Posted By Michael Johnston,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
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Since 1897 theNational Electrical Code(NEC), the world’s most widely used and adopted code for the built environment, has been the source for electrical installation requirements in all types of occupancies and applications, including dwelling units. The NEC was originally developed as a result of united efforts of various insurance, architectural and allied interests, and in 1911 the NFPA assumed stewardship of the NEC. As stewards of the Code, NFPA is responsible for its development and publishing and promotes its use and adoption as the sole source of comprehensive electrical installation requirements for all occupancies in accordance with its scope as stated in Section 90.2. Within the NEC there are numerous electrical installation requirements that apply specifically to one-, two-, and multi-family dwellings. These dwelling-unit-specific requirements reflect the fact that in most cases, particularly with one- and two- family dwellings the layout and design of the electrical system is the responsibility of the installer. Although Section 90.1(C) specifies that the Code is not intended to be a design document, the fact of the matter is that in all dwelling units, an electrical system that complies with the NEC will be safe and in most cases will be adequate for good service. When one looks at the membership of the NEC code-making panels responsible for the article in which the dwelling unit requirements reside, there are technical expertise and balanced representation that enable the Code to stay current with a dynamic and ever progressing electrical industry.
Photo 1. This fairly large one-family dwelling is served by a 400-ampere service and includes approximately 3800 square feet
Photo 2. Another typical one-family dwelling has roughly 3000 square feet of habitable floor space and is supplied by a 200-ampere service
Some codes and standards are occupancy-based or, in some cases, they are occupancy specific. An example of an occupancy-based code is NFPA 101. The first ten chapters of this document are dedicated to general and specific requirements on subjects ranging from means of egress to features of fire protection. The remaining chapters (11-42) cover various occupancy types and how to apply the requirements of Chapters 1-10 to these occupancies. There are codes and standards, the scopes of which focus exclusively on one specific type of occupancy. NFPA 99, Standard for Health Care Facilities is an example of a sole occupancy set of requirements. In general, Chapters 1-4 of the NEC are not considered to be occupancy specific unless otherwise indicated by a requirement. In other words the majority of the requirements in these chapters apply to electrical installations regardless of where they are installed. Chapters 5, 6, and 7 do provide more focused requirements for special occupancies, special equipment and special conditions and, according to the hierarchal arrangement of the Code specified in Section 90.3, these requirements may amend or modify the general requirements contained in Chapters 1-4.
Photo 3. This typical wiring rough-in using non-metallic sheathed cable has supports provided at outlet box and also at required intervals
There are numerous requirements in the NEC, particularly in Chapter 2 that are only applicable to dwellings. Examples of such requirements include the GFCI requirements in 210.8(A), the receptacle spacing rules in 210.52 and the lighting outlet requirements of 210.70(A). The text of these requirements clearly indicates that their application is to dwelling units only. In some cases there are requirements that apply to one- and two-family dwellings or to multi-family dwellings, but the fact of the matter is that for the most part the requirements in the NEC are not occupancy limited (see photos 1 and 2).
Photo 4. A close view of the device outlet box shows the rough-in stages in a typical dwelling unit
In 1968 under the direction of the NEC Correlating Committee, an ad-hoc committee developed NFPA 70A, Electrical Code for One- and Two-Family Dwellings. This code was developed as a convenience to those members of the electrical industry whose primary focus was electrical installations in one- and two-family dwellings. The requirements in this code covered the most typical wiring methods and materials used in the construction of one- and two-family dwellings. In those cases where a wiring method or piece of equipment was not covered in NFPA 70A, the rules of theNECwere to be applied. The first edition of NFPA 70A was based on the 1968 NEC and revised for each subsequent Code cycle until 1993. The requirements in NFPA 70A were directly excerpted from the NEC with only editorial changes to reflect the limited scope of the document. In addition, the chapter arrangement and section numbering sequence of the NEC was retained for 70A so that the Code had the same look and feel as the parent document. This approach ensured that inspectors and installers were on the same page in respect to technical content, presentation and arrangement.
NFPA 70A was not revised for the 1996 and 1999 NEC cycles. However, for the 2002 cycle NFPA 70A has been revised and like its predecessors is a document containing excerpted text from the current edition of the NEC. The requirements are arranged in the same sequence as they appear in the NEC, an important concept that ensures inspectors and contractors are "”speaking the same language.”" There has been an expansion of the topics covered in this edition of 70A that reflects the changing electrical needs of today’s homeowner. As with the past editions, the default position is to refer to the NEC for those specific installation requirements not contained in NFPA 70A.
Photo 5. In this typical two-family dwelling underground service, two utility meters are shown as well as other utilities supplying each dwelling
The International Codes Council (ICC) has also developed a series of codes that are available for adoption and use in the construction industry. One of the codes included in this family of codes is the International Residential Code (IRC), which was developed in 1996 and is actually referred to as the "”International Residential Code for One- and Two-Family Dwellings.”" The International Residential Code includes the requirements for construction, alterations, repairs, movement, enlargement, replacement, use and occupancy, locations, and removal or demolition of one- and two-family dwellings, and multiple single-family dwellings (townhouses) not more than three stories in height with separate means of egress and associated accessory structures [IRC 2000 R101.2].
The purpose of the IRC is to provide minimum requirements to safeguard life or limb, health and public welfare. The IRC includes minimum code requirements for all of the separate disciplines (trades) including electrical code requirements related to one- and two-family dwelling occupancies [R101.3]. The purpose of the NEC is specific to the practical safeguarding of persons and property from the hazards associated with the use of electricity [90.1(A)]. Both codes are directed to essentially the same purpose of safety. The ability to effectively apply the codes to installations and systems is a vital part of the electrical safety system in North America and beyond.
Table 1. A summary of how the IRC 2000 is organized. Part VIII of the IRC is titled "Electrical" and includes ten chapters 3 through 42.
Table 1 is a summary of how the IRC 2000 is organized. Part VIII of the IRC is titled "Electrical” and includes ten chapters—33 through 42.
It is important to provide a bit of background information related to the electrical provisions contained in the IRC. First, it must be understood by both the installer and the inspector that Part VIII (The Electrical Requirements) of the IRC is produced and copyrighted by the NFPA and is based on the requirements of the 1999 National Electrical Code. In simple terms, the requirements contained in the IRC 2000 are derived from the requirements applicable to one- and two-family dwelling electrical systems contained in the NEC presented in a format that is compatible with ICC developed codes. The technical content of the requirements are based on the NEC but there is a different numbering scheme in the IRC that makes things a bit more difficult to find. There are two real important sections contained in Chapter 33 of the IRC that include vital information about the scope and applicability. A close look at Sections E3301.1 and E3301.2 provide the framework for proper application of the rules in Part VIII.
What’s Covered and What’s Not Covered?
The electrical provisions in Chapters 33 through 42 of the IRC are intended to cover the most typical installations of electrical systems, equipment and components installed indoors and outdoors at one- and two-family dwellings. The scope includes the requirements for services, power distribution systems, luminaires (fixtures), appliances, devices and other electrical appurtenances. The IRC includes the requirements for electrical installations and equipment most commonly encountered in the construction or alteration of one- and two-family dwellings and associated accessory structures. The IRC includes provisions for electrical services rated up to 400 amperes that are single-phase, 120/240-volts. Any electrical service beyond those ratings is required to fall under the provisions of NFPA 70, National Electrical Code. Other wiring methods and materials and subject matter that are not covered by the IRC but are covered by the rules in the NEC are allowed by the IRC. [See photos 3 and 4]
IRC defaults to NEC
Photo 6. Here is a closer view of photo 5
The IRC includes the requirements related to the most common one- and two-family dwelling electrical systems and is intended to be used with the NEC in order to provide a complete set of electrical installation requirements for residential occupancies. If any requirement of the NEC is omitted or not included in the IRC, this omission is not to be construed as prohibiting the use of such omitted equipment or installations. The scope of the IRC clearly indicates that electrical systems, equipment or components that are not specifically covered by Chapters 33 through 42 must comply with the applicable provisions of the NEC. Basically, this means that the provisions of Part VIII apply and where the installation is beyond the scope as outlined in E3301.2 of the IRC, the requirements of the NEC are applicable by default. An example is central air-conditioning equipment covered within the scope of Article 440 of the NEC. One should also be aware of any local amendments that may be applicable in addition to these minimum requirements. Generally, local amendments will exceed the minimum provisions by national codes and standards based on particular conditions that require such amendments.
Comparison to the NEC
Photo 7. A typical combination smoke/carbon monoxide detector in a dwelling
The rules in the IRC are primarily derived from the NEC requirements that apply to one- and two-family dwelling electrical systems. Generally, other than a different numbering system, the requirements are the same but in some cases may be worded a bit differently. There are a few differences between the two codes that should be emphasized. This article is not intended to be all inclusive of differences between the two documents. The differences are primarily limited to the limitations in scope and how the rules are presented to the user. The first major difference is the limitation of service size and voltage to 400-amperes, single-phase, 120/240-volts. The NEC does not limit the size of service for dwellings. Remember the IRC is intended to cover the most commonly encountered electrical installations in one- and two-family dwellings. Another difference between the two codes is that many of the rules found in the NEC sections are presented in the IRC in tabular form; that is, the requirements are the same, they just appear in the form of a table rather than a section. Look at the following comparison as an example. The wiring methods for a dwelling are provided in the NEC in Chapter 3. Each wiring method has an article assigned to it and within that particular article the uses permitted, uses not permitted, support and installation requirements, etc., can be found. In the IRC, specifically Chapter 37 Wiring Methods, there is a table that lists all allowable wiring methods (Table E3701.2). Looking further into this chapter there are three additional tables, E3701.4, E3702.1, and E3703.1.
Photo 8. This smoke detector in a dwelling is connected to a listed fire alarm/burglar alarm system
Table E3703.1 and its applicable notes parallel the requirements of NEC Table 300.5 for minimum cover requirements of underground electrical installations. Tables E3701.4 and E3702.1 include the requirements for wiring methods. Table E3701.4 includes the wiring method across the top of the table and the allowable application for the wiring methods listed in the vertical column on the left. This table provides the uses permitted and uses not permitted for the particular wiring methods. This differs from the NEC but only in how the information is presented. The uses permitted and uses not permitted are the same, just provided in tabular form all on the same page.
Table E3702.1 and its applicable notes provide the requirements for installation and protection of the wiring methods. The wiring methods are included across the top of the table and the vertical column on the left provides the installation requirements. This column includes the general installation requirements and specific rules relating to securing and supporting the particular wiring method allowed, such as bored holes in wood framing members, number of 90-degree bends in a conduit run between junction or outlet boxes, and maximum intervals between supports for the wiring method used. This differs once again from how the NEC presents the requirements, but the rules are the same. They just appear in one table rather than in the individual wiring method article.
Photo 9. This large living space in a dwelling has two large ceiling paddle fans in the center
Another table provided in the IRC is Table E3808.12, which is included in Chapter 38 and provides the minimum size equipment grounding conductor for circuits. This table essentially provides the same minimum sizes that are provided by Table 250.122 of the NEC. The primary difference is that Table E3808.12 is limited to circuits rated up to 400-amperes.
The IRC also provides the requirements for service, feeder, and grounding electrode conductor sizing in Table E3503.1. Essentially, this table is an expanded version of NEC Table 250.66. Table E3503.1 not only includes the minimum size grounding electrode conductor required for the service, but also lists the minimum size service-entrance conductor and allowable ampacity for the service-entrance conductor.
The minimum service load calculation requirements are also provided in a tabular format. The minimum size service is 100-ampere and the load calculation is performed similar to those in Article 220 of the NEC. Table E3502.2 is required to be used for calculating the minimum load for ungrounded service conductors and service devices that serve 100 percent of the dwelling unit load. Ungrounded service conductors and equipment that serve less than 100 percent of the dwelling unit load are required to follow the sizing requirements for feeders provided in Chapter 36.
Other sections in the IRC that include the requirements are presented in tabular format. It takes a bit of referencing back and forth from the NEC to the IRC but once located, the information provided, whether in text or table form, has its technical basis in the NEC.
The IRC also includes definitions in Chapter 34. These definitions are derived from Article 100 and are essentially the same. A few definitions, like authority having jurisdiction, and some that would not apply to one- and two-family dwelling electrical installations are not included. The IRC includes another general definitions chapter that applies to the whole code (see Chapter 2 of the IRC). Administrative provisions are located in Article 80 of the NEC and Chapter 1 of the IRC. Information about the scope, applicability, enforcement, permits and plans, powers of the building official, etc., are also found in Chapter 1.
Provisions for Smoke Alarms
The Building Codes generally require rules for fire protection systems and smoke detectors. Building codes will reference NFPA 72 in addition to the specific requirements of the applicable building code. The IRC is no exception. Although smoke alarms and detectors are not a requirement in the electrical provisions of the IRC, the requirements for smoke detectors can be found in Section R317 of the IRC. This section includes the rules for placement, listing requirements, alterations and repairs, and the required power source. Basically this section requires the equipment to be listed and installed in accordance with R317 and the household fire warning equipment provisions of NFPA 72.
Smoke detectors are required in each sleeping room, outside of each sleeping room, and in each additional story including basements and cellars but not crawl spaces. Where more than one smoke detector is installed to meet these requirements, all smoke detectors within the dwelling unit require an interlock or interconnection in a suitable manner that upon activation of one, all alarms will be activated.
The wiring for these smoke detectors/alarms must follow the applicable provisions of Part VIII (Electrical) of the IRC. Smoke alarm equipment installed in new construction requires a primary source of power supplied by the building wiring and must include a battery backup. Smoke alarms that operate on batteries only are permitted under regulation R317.1.1 for remodels or for buildings that do not have commercial power supplied to them. It is important to consult the local authorities relative to any smoke alarm requirements that may also apply.
Cross Reference Information
Electrical requirements are critical to safety of persons and property and serve as the basis for development of codes and standards for safety. Many involved in the electrical field know and understand the provisions of the NEC that apply to one- and two-family dwelling electrical systems. Where jurisdictions adopt the IRC into law, there will be assimilation challenges for those installers and inspectors involved with one- and two-family dwellings. Hopefully this article will reduce some of the anxiety levels created by fear of having to relearn the arrangement of electrical installation requirements.
There is a built in fast finder in the IRC that is similar to the NEC. It includes a contents and an index. The index references section numbers and the contents references page numbers. The IRC also includes a cross-reference between the IRC sections and the NEC sections. IAEI has also included the IRC-NEC cross-reference information in the 2002 IAEI Ferm’s Fast Finder to assist users of these codes.
In today’s world it is not uncommon at all for a dwelling unit electrical system, particularly the service equipment and first level of feeder distribution, to resemble that of a small to mid-sized commercial occupancy. One-family dwellings supplied by 2000-ampere services, 3-phase 208Y/120-volt services, and special equipment such as large air-conditioning and central heating units are not unusual. Services rated at 400 amperes are no longer a surprise to installers and inspectors. Elaborate communication and computer networking systems serve the needs of today’s home office. With this in mind, installers and inspectors involved with dwelling unit electrical systems of this magnitude are using more of the NEC requirements than ever before. For this reason, abridged sets of electrical requirements, such as the IRC, will inevitably require the inspector and installer to refer back to the NEC in order to access all of the applicable requirements.
IAEI is concerned about electrical safety as one of its primary objectives across all codes and electrical safety standards. IAEI is an international organization that has a responsibility to represent the electrical inspector in national and international affairs. One of the key benefits of being an IAEI member includes the access to critical industry information. This article was put together to provide valuable insight into the prospect of having to face the learning curve inherent to using the reorganized electrical provisions of the International Residential Code (IRC) and to help reduce anxiety levels for those having to install or inspect in accordance with the rules in the IRC. One can rest a bit easier with the understanding that the IRC electrical requirements, although unfamiliar in presentation, have been developed through the technical expertise of the National Electrical Code Committee. Some jurisdictions have adopted the IRC with its electrical provisions while the trepidation of relearning the location of familiar requirements has resulted in a number of adoptions without Part VIII and reference the NEC for the electrical requirements. IAEI feels strongly that information relative to finding and applying the electrical code requirements in both the NEC and the IRC is important in the interest of electrical safety. Providing this information is a continuation of the commitment of the IAEI to provide effective products and information for installers, inspectors, engineers, etc., all in the interest of electrical safety.
Always consult the local authority having jurisdiction for the code(s) that applies to one- and two-family dwellings in your area.
Read more by Michael Johnston
Posted By George Gregory and Alan Manche,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
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AFCIs are not new, but they are newly applied under theNECrules. A variety of questions have arisen regarding where they must be applied, whether to expect unwanted operation, and how to test and service installations. This part of the two-part article answers some of those questions.
Electricians, contractors and users should be aware that AFCIs are installed in locations that the standard circuit breakers are installed. They can be retrofitted into existing loadcenters and panelboards. Electrical connections are similar to those of a circuit breaker GFCI in that they have a load-neutral connector and a pigtail connection to the panel neutral bus.
Photo 1. Branch/circuit-breaker type AFCI
It should be very difficult to cause an unwanted tripping condition in a dwelling unit branch circuit. When tripping occurs, it is most likely a result of an arcing condition or an improperly wired circuit. The AFCI is designed to trip when certain conditions likely to cause a fire exist in the circuit. There has been relatively little experience in locating these conditions. This paper provides some guidelines that may be helpful. Part I of the article lists conditions under which the AFCI is designed to trip. The discussion focuses on the branch/feeder AFCI, which is the only commercially available AFCI.
Applying AFCIs under NEC 210.12
As mentioned in Part I of this article, theNEC2002 retained, with only minor revisions, the requirement of the NEC 1999 that AFCI protection be required on branch circuits that supply receptacle outlets in bedrooms. One revision confirmed that the AFCI must protect the "entire” branch circuit. Another replaced the term "receptacle outlets” with simply "outlets” and required that all outlets—including those for lights, fans and smoke alarms—be protected as well as receptacle outlets. These changes affirm that NEC Code-making Panel 2 (CMP-2) intends that fixed wiring be protected and that all wiring associated with bedrooms be covered by the rule.
As regards what must be protected, the requirement is clear as written: "All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter listed to provide protection of the entire branch circuit.”1 This includes outlets for receptacles, for lights, for fans, and so forth in circuits that supply bedrooms.
Retrofit applications in 2-wire circuits
A branch/feeder AFCI (circuit breaker type) provides good protection for 2-wire circuits. It provides for detection of a low-level short circuit of 75 amperes or above that would not be detected by an overcurrent protective device. It also provides detection of an arcing ground fault occurrence of 5 amperes or above. Note that commercially available AFCIs actually detect arcing ground fault of 50 milliamperes and above even though 5 amperes is the standard requirement. This protection is as valid in 2-wire circuits as in 3-wire circuits that include the grounding conductor. The difference is that with the added grounding conductor in the 3-wire circuit, an arc of any level may reach the grounding conductor and be detected at levels below 75 amperes, which provides a degree of protection not available in 2-wire circuits.
Required locations under the NEC
Article 100 of the NEC defines a dwelling unit as: "One or more rooms for the use of one or more persons as a housekeeping unit with space for eating, living, and sleeping, and permanent provisions for cooking and sanitation.” AFCIs are required in specified circuits that supply dwelling unit bedrooms. The following points are from questions that have arisen regarding circuits to be protected.
Hotels and dormitories
One question that has arisen is whether hotel or motel rooms and dormitories are considered dwelling units. The rule must be interpreted by the authority having jurisdiction (AHJ). If the AHJ considers these units dwelling units, they must be so considered for NEC 210.12. One way to make this judgment is to consider whether the units would constitute a dwelling unit if the facility were placed under new ownership and occupied as apartments or condominiums.
Smoke detector circuits
Circuits supplying smoke detectors in bedrooms fall under the category of bedroom outlets. Recall that the purpose of the AFCI is to address fire causes. If the potential fire cause is in the smoke detector wiring, the first approach for protection against fire should be to clear the potential cause. Further, listed smoke detectors are required to have battery back up, so that power to the smoke detector is not dependent on the presence of power from the utility.
Whether bedroom closets are part of the bedroom is a judgment to be made by the AHJ. However, it is clear that the intent of 210.12 is to provide protection for the entire bedroom. When the closet is an integral part of the bedroom, a safe approach would call for the closet wiring to be protected just as other parts of the bedroom.
Although not required under the NEC, AFCIs are suitable for use in commercial applications in circuits for which they are rated.
Tripping Causes on Installation
Causes of tripping of branch/feeder AFCIs are listed in Part I of this article. Understandably, it is frustrating to install a device and find that it trips as soon as it is turned on. It is important to understand that where single-pole AFCIs are used, the neutrals of two or more circuits cannot be shared, mixed or crossed. Also, if the neutral is grounded on the load side of the AFCI, the AFCI may trip.
Because there were a significant number of reports of AFCIs tripping on installation, Square D re-contacted those who had reported the tripping after the initial inquiry from them. The following is a list of the findings.
- 4 cases were unresolved.
- 1 was an application problem in which equipment of two manufacturers was mixed on the job. The AFCI worked fine and continues to do so.
- 6 were resolved by reading the instructions. The callers had not initially understood how the AFCI was to be used.
- 1 was a bad appliance, a room air conditioner.
- 23 were wiring problems broken down as follows.
1 problem at a connector in which wires were too close
4 crossed neutrals
7 shared neutrals
9 grounded neutrals
2 shared neutrals also grounded
Crossed neutrals are defined here as neutrals from multiple circuits either crossed or touching. Shared neutrals are defined here as multi-circuit neutrals.
Reported difficulties in troubleshooting installation problems are an indication of a learning curve and are not a reflection on poor performance of the AFCI. Today’s AFCIs are performing their detection function properly and are finding problems that should be corrected. There is some resistance to this change as is to be expected with any change. However, this small and informal survey indicates that installers are learning the issues that are uncovered by AFCIs and that they can be found and corrected. When the circuit is corrected, not only is the circuit correct, it also has additional AFCI protection operating to help retain it free of hazardous arcing.
Single-pole AFCIs cannot protect circuits in which the neutral (grounded circuit) conductor is shared or mixed. The reason is that current flowing out and returning is monitored for the presence of arcing faults. When single-pole AFCIs are applied, the circuit must have a distinct hot and a distinct neutral conductor. Otherwise, the AFCI cannot distinguish arcing ground-fault occurrences.
Table 2. 1999 adoptions and adoption states (2002 and 1999)
Contractors and users should understand that thereare some drawbacks to using shared neutrals. For example, if a 2-pole, common-trip version is used, then both circuits are interrupted during a fault. If the 2-pole, common-trip version is used, then both circuits are interrupted during a fault. If the 2-pole circuit breaker has independent trip, then when a circuit is tripped and an outlet device is removed (assuming a dead circuit), if the home run is split at that point, the wiring in the box is not really dead. Another example of shared neutral wiring disadvantages is the result if the home run neutral is lost—a motor load will take one side of the circuit to zero, putting the loads on the other side to 240 volts. This tends to play havoc with many 120-volt devices. Further, cable manufacturers are apparently planning cables that contain four wires plus ground for exactly this kind of application.
Availability of test equipment has been questioned for three purposes:
a. To verify that the circuit has been installed properly so that contractors can demonstrate that their work has been done competently.
b. To verify that the AFCI is functioning properly.
c. To trip an AFCI from a load circuit in order to identify which AFCI is in the circuit.
We will discuss each item briefly.
Verification of the installation
The authors are not aware of special equipment available to test the circuit for proper installation beyond that which has been available without the AFCI. If wiring is installed competently, there should be no reason for any testing that is not done for a circuit without an AFCI. However, there are two possible practices that can be used to test the installation, if a test is desired.
1) Probably the best test is to install an AFCI, at least temporarily in the circuit. For this test to be effective, the circuit must be complete, since it must be energized as in service with 120 volts. Use the test button to verify that the AFCI is functioning properly. Then leave the AFCI in the energized circuit for some period of time. If it does not trip, that is an indication that the circuit is acceptable.
2) As with any installation, an insulation resistance (Megger device) test can be done to verify that the wiring and connections are properly insulated. With this test, high voltages are applied. Be sure to keep personnel away from circuits being tested and follow safety practices described in NFPA 70E, Part II.
To perform this test, disconnect all loads and verify that unconnected wire ends are insulated. Disconnect the load wire to any AFCI or GFCI in the circuit because these devices may be damaged by high voltage. Use an insulation resistance tester that will apply a direct current voltage of at least 500 volts to the circuit under test. All resistance readings should be at least one megohm (1,000,000 ohms). A successful test will indicate that the insulation is intact and initiation of an arc would be highly unlikely for the portion of the circuit tested.
Recognize that neither of these tests will identify loose connections. Good workmanship is required as always.
Verification of the AFCI
The most effective test is the self-test supplied with the AFCI. See the instructions supplied with the AFCI by the manufacturer. In accordance with UL 1699, this test "simulates an arc such that the arc detection circuit or software is caused to detect the simulated arc.” By doing so, it tests all of the AFCIs systems and tripping parts. An external tester is not necessary.
The authors are not aware of commercially available testers other than those mentioned below that trip the AFCI by applying a ground fault.
Tripping the AFCI from a load
There are several devices being marketed that will trip the AFCI by applying a ground fault on the system. Be aware that devices that are not listed for this purpose may be creating a potential shock hazard by creating a ground fault of sufficient current to trip the AFCI.
Finding the cause of AFCI tripping
One of the most frequently asked questions is about how to find the cause of tripping when an AFCI trips. There is no single correct answer to this question. An orderly search is probably the best approach. We are not aware of specialized equipment that would help locate a problem. The skill and experience of the electrician will help. Remember that the circuit breaker AFCI will trip from an overcurrent sensed by the circuit breaker or from an arcing occurrence sensed by the AFCI function, including a ground fault.
The AFCI function will be sensing an arc that occurs because insulation or isolation is not adequate. The problem or fault may be in one or a combination of these three conditions:
3) Series arc in broken or separated conductor (could be a loose connection). Note that the branch/feeder AFCI will not generally detect a series arc because series current is usually below the detection level.
Here are some steps that may be useful:
a) Gather information from people who have used the circuit regarding any buzzing noises, visible arcing, the odor of smoke, or similar indications of improperly operating or defective appliances or equipment. This information may lead to the fault location. If arcing is suspected in an extension cord or a cord-connected appliance, immediately unplug the suspected unit.
b) The most likely cause of tripping in a new installation is wiring. Check for neutral (grounded circuit) conductors that are shared or crossed with those of other circuits, or neutral conductors that are grounded on the load side of the AFCI.
c) Unplug all appliance and extension cords connected in the circuit. If tripping continues to occur when the AFCI is turned on, the fault is in the fixed wiring system.
d) Similarly, turn off all fixed appliances such as lights and ceiling fans that have switches. Since these circuits cannot be fully disconnected (line, neutral and ground), tripping occurrences with their switches turned off does not necessarily mean that they are fault free.
e) If the AFCI does not trip when all plugs are disconnected, turn on the AFCI again and reconnect the plugs one by one. Then turn on fixed lights and appliances. This procedure may locate the faulted cord or appliance.
f) Because arcs are sometimes sporadic, turning off the circuit may temporarily clear the arc and it may not immediately reappear when the circuit is re-energized. For this reason, the arc may not be located by unplugging and reconnecting appliances. If the arc has been located to be in the fixed wiring system, or if the arc has not been located by removing plug-in loads, some of the following techniques may be helpful.
- Examine appliance cords, plugs and equipment carefully for indications of damage.
- With the circuit de-energized, examine connections to the AFCI, receptacles, lighting fixtures and other appliances.
Note: De-energize the load center by turning off the main disconnect, if possible, before conducting the following checks. By means of a reliable voltmeter, verify that voltage is not present.
g) Apply the insulation resistance test described in a response to a question above to check for insulation adequacy line-to-neutral, line-to-ground and neutral-to-ground. Alternatively, use an ohmmeter to check for electrical continuity line-to-neutral, line-to-ground and neutral-to-ground. Continuity indicates presence of a fault. The insulation resistance check is the preferred method.
h) Indication of adequate insulation in a circuit that has been identified as having an arc fault may point to a series fault, that is a broken conductor or a loose connection.
i) The line-to-ground sensing is for small leakage current of about 50 milliamperes (0.050 amperes) and above. It may not be visible as an arc. Any technique used to find a ground fault would be useful for locating an arc to ground.
j) Once the fault is located, damage must be repaired or improperly operating equipment or appliances must be replaced.
k) In most cases, the steps noted above will help locate the fault. It is important to recognize that the AFCI has provided an indication of a condition that could become a fire hazard. Do not continue to use the circuit without a correction.
The introduction of AFCIs is a change. There is a learning curve for the entire industry. Through this change, it is clear that AFCIs are finding problems with installations, both in older upgrades and in new construction, in fixed wiring as well as in extensions to loads. The data indicates that there are many potential fire causes that the AFCI will help avoid becoming fires. When they are applied as intended, we will see results in more potential fire causes corrected.
1 Section 210.12(B),National Electrical Code2002, (National Fire Protection Association, Quincy, MA), p. 70-54.
Read more by Alan Manche
Posted By Jeffrey S. Sargent,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
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Every electrical inspector has been there, the first time out to approve an electrical installation as the "authority having jurisdiction.” Realizing the importance of his or her role in the safety chain, new electrical inspectors, and for that matter all electrical inspectors, want to perform their duties with a thorough and professional approach. In most cases the electrical inspector is the independent public safety advocate with no stake in a particular project other than to ensure that the end result is a safe installation that complies with all of the applicable NEC requirements. In some cases inspectors may be working as a "clerk of the works” or project inspector for a private concern. The bottom line is, whatever the role of an electrical inspector is for a particular installation, he or she is charged with the responsibility of quality assurance, and the benchmark on which compliance is judged most generally is the requirements of the NEC.
Photo 1. Home under construction
Where to Start?
Electrical inspectors bring varying degrees of background and expertise to their positions. Many have been electricians prior to accepting the role as electrical inspector, but that fact alone does not ensure a seamless transition from installer to inspector. Although they may be well-versed in the NEC requirements from past training and experience, when they are placed in the position of being the authority having jurisdiction (AHJ) their electrical world inevitably expands into the full scope of what the NEC covers. Many electricians have a specific focus as an installer. Industrial electricians may never have used and applied the rules for dwelling units or manufactured homes, and residential electricians probably did not perform many installations involving the installation of large separately derived systems or capacitor banks. Now, in the new role as the electrical inspector, this person is expected to be an expert in all facets of the NEC. Electrical inspectors soon realize that their new position has put them in a new learning curve and most experienced electrical inspectors will tell you that this learning curve is on-going and ever-changing throughout their electrical inspection careers. Certainly there are training and certification programs that enable electrical inspectors to enhance their job performance. However, new and seasoned electrical inspectors will inevitably encounter an installation that is new ground.
When put into the position of having to approve an electrical installation that one has not previously encountered, either as an electrician or as an installer, the logical question is where to start? From a very general sense, a logical approach to the inspection and approval process is determined based on the phase of construction a project is at. Certainly the status of the construction project will direct the focus of the inspection. For new building projects, inspections are generally made incrementally as the building is constructed. Depending on the size of the building and more importantly the complexity of the building’s electrical system, the number and focus of electrical inspections will differ.
The major considerations for "rough wiring” inspections differ from the major considerations for a "final inspection.” Putting this all together into a logical and thorough approach is the challenge faced by the electrical inspector. He or she is compelled by the responsibility placed in his or her hands to ensure that the building electrical system is essentially free from fire and shock hazards.
A systematic approach often will involve the use of some kind of written or mental checklist. As inspectors gain experience in the multitude of electrical installations that they are exposed to, there is a natural maturation in how they perform their duties. Experience promotes efficiency and thoroughness. A key component to this increased efficiency and thoroughness is the development of the inspector’s "inspection system.” Many electrical inspectors approach the inspection task using mental checklists. The development and refinement of these checklists evolves with experience. Like any job, one’s proficiency develops with experience and this definitely holds true for electrical inspectors. Tasks that were at one time daunting become routine through the lessons of experience. But the question remains, as a new electrical inspector where does one start in order to develop a polished inspectional procedure?
A Tool for Inspectors
Unlike apprentice programs for training electricians, the training of electrical inspectors is generally far less formal or structured. For those who have entered the inspection field from a background in electrical installations or design, there is generally a thorough understanding of the NEC and how electrical systems are put together. This background provides a solid foundation for an electrical inspector to build on as he or she changes perspective from installer to approver. Organizations such as the IAEI that promote uniform application of the NEC via their educational programs offered by their local chapters and the International office help electrical inspectors make this transition. This type of meeting provides an excellent forum for the dissemination of knowledge regarding the NEC, however there was a need for an inspectional job-aid that could be used by electrical inspectors on a daily basis. The National Fire Protection Association (NFPA), the developer and publisher of the National Electrical Code has developed a tool to meet this need.
First published in 1999 and based on the 1999 edition of the NEC, the Electrical Inspection Manual with Checklists was developed to fit the needs of anyone who installs or inspects electrical installations. Endorsed by the IAEI, the purpose of this manual is to provide inspectors and installers with a compilation of electrical inspection checklists. These checklists range in coverage from general requirements for all electrical installations to more specific checklists based on type of occupancy, type of equipment or type of location. The checklists are an assemblage of electrical installation requirements that pertain to a respective type of occupancy or equipment and are not intended to dictate a specific inspection order or procedure. Electrical inspectors are individuals and need to develop an inspection system they are comfortable with. There is not one inspection template that will be suitable for every inspector. What works for one inspector will not necessarily work for another. The bottom line is that the inspection is performed efficiently and comprehensively. Use of the Inspection Manual checklists will assist the inspector in developing an approach that meets this objective.
The checklists are comprehensive and in most cases provide all of the necessary references to the NEC requirements that apply to a particular installation. In some cases all of the items in the checklist may not be applicable to a given installation. On the other hand, the checklists are not intended to imply that there may not be other NEC requirements that are applicable to a given installation.
How the Manual Works
The foundation of the manual is the checklists. Each checklist contains a number of inspection activity items and there is a cross-reference to the applicable section of the NEC. An important feature of the manual is the brief explanation that is provided for every inspection activity item. This commentary provides insight on the application of the particular NEC requirement that the inspection activity is based on. This commentary material is numerically linked to the number of the inspection activity item in the checklist. Table 1
An important concept in using the Inspection Manual is its structure. Like the hierarchal arrangement of the chapters within the NEC, the chapters in the Inspection Manual are arranged to provide general overall considerations regarding electrical installations in the first five chapters, while Chapters six through twelve contain specific occupancy or equipment checklists. As an example, the checklist in Chapter 2 of the Inspection Manual contains inspection items from Articles 90 and 110 of the NEC. These checklist items are general requirements that will apply to most electrical installations that the inspector will encounter. However, the checklists in the latter chapters are more specific and do not have the broad scope of the up-front chapters. Like the NEC, it is necessary to use more than one part of the book for any given installation. Chapter Six on Dwelling Units and Mobile/Manufactured Homes is the only chapter that for the most part is self-contained and does not require the use of other chapters. The decision to make Chapter Six a "stand-alone” chapter was based on the fact that in most cases electrical inspectors who work for a city or town will inspect a large number of dwelling unit electrical systems.
Additionally, each checklist contains "key questions” that are germane to that particular inspection checklist occupancy or equipment. The purpose of the key questions is to put the inspector "in the mood” for that particular inspection by providing some general considerations and items to be aware as the inspection is being performed. Like the commentary provided for each of the inspection activities, background information is provided for each of the key questions and uses alphabetical links. The checklists have many different applications. An individual electrical inspector can use them as a self-training tool for developing a personal inspection protocol. The checklists can be used as a template for training groups of electrical inspectors or they can be used during the field inspection process where a comprehensive written record of a particular installation is required.
Using the Dwelling Unit Checklists
The inspection checklists for dwelling units in Chapter 6 provide a slightly different approach than the checklists contained in the other chapters. Chapter 6 takes a residential project from start to finish and provides checklists covering "rough” and "finish” inspections. Another feature of this chapter is that it provides a breakdown of specific rooms or areas within or associated with a dwelling based on the specific NEC requirements for those areas. Beginning with some key questions that are intended to give the inspector some general points to focus on as the project proceeds, the checklist next provides some general requirements that apply throughout the dwelling unit, and then it continues with specific NEC requirements for kitchens, dining rooms, bathrooms, other habitable rooms, hallways, stairways, closets, laundry areas, basements and attics, garages, and outdoors. This area approach provides the inspector with the NEC requirements that are unique to that specific area. This reflects the fact that the NEC, particularly in Article 210 provides more requirements for specific locations within a dwelling than for any other type of occupancy. This type of approach is taken in the NEC since in most cases, the electrical system of a dwelling is laid out by the installer.
The dwelling unit checklist then proceeds into the requirements applicable to the installation of the electric service, the installation of any feeders, and the grounding and bonding provisions for the service equipment. This portion of the checklist also provides the requirements for panelboards that are supplied by service or feeder conductors.
The "finish” inspection checklist is arranged similarly to the "rough” wiring checklist. Beginning with a number of general requirements that apply throughout the dwelling, the checklist proceeds with the room-by-room approach, ensuring that the completed installation in each room meets the NEC requirements that are unique to that area. For instance, during the rough wiring inspection of the kitchen the inspector needs to verify the installation and proper use of the minimum two small-appliance branch circuits, while during the final inspection the inspector is verifying that GFCI protection has been provided for the receptacles serving the kitchen counter area. On the same vein, within the dwelling unit bathroom(s) the inspector has verified the presence of the 20-ampere circuit for the bathroom receptacle outlets, while during the finish inspection it can be verified that GFCI protection has been provided for the bathroom receptacles.
As part of the final inspection checklist, there are also requirements for service equipment and panelboards supplied by feeders. Among the items covered in this portion of the checklist are the verification of the completed grounding system and the identification of the circuits within the panelboard(s).
New for the 2002 edition of the manual is a checklist that covers the NEC requirements for manufactured home site supply wiring. For new manufactured home installations, the electrical inspector does not typically inspect the factory-installed wiring, however the site supply installation and any additional branch circuit or feeder installations are subject to field inspection. Also new for this NEC cycle is the Pocket Guide to Residential Electrical Inspections. This abridged version of the Electrical Inspection Manual contains all of the dwelling unit checklists and associated commentary. In addition, the checklists for general wiring requirements, wiring methods, grounding and bonding and swimming pools are also included.
No two electrical inspectors will perform their field inspections exactly alike. Inspection processes and techniques differ and often are dictated by construction conditions. Thus it is often not possible to "package” the inspection of a dwelling as is neatly laid out in the checklists. This was never the purpose of the book. The purpose was to lay out the applicable requirements in a list format that can be used as an aid to inspectors of dwellings and other occupancies and electrical equipment covered in the manual to develop a system for performing thorough, efficient and effective electrical inspections. As was previously stated, experience and an upfront understanding of how electrical systems operate are two of the most important factors to having a strong foundation on which an inspector can grow from. After all, the method by which the inspection is performed is not nearly as important as is how well the inspection is performed.
Read more by Jeffrey S. Sargent
Posted By Ken McLennan,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
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Section 18 of the CSA Canadian Electrical Code (CE Code) covers the installation of equipment and wiring in locations considered hazardous because of the presence of ignitable or explosive materials. Such locations are divided into three classes:
Class I, which contains explosive gas or vapours
Class II, which contains combustible dust
Class III, which contains combustible fibres.
A major change in the 18th edition of the CE Code, published in 1998, introduced the zone system of dividing Class I locations into three zones instead of the two divisions used in previous editions. This was a significant change, affecting all electrical installations in hazardous locations, and is still not entirely understood by everyone.
It would not be appropriate to simply identify the revisions brought about by this change without discussing the principles behind them.
The Division System
Originally, Class I locations were not divided. A location that was subject to the presence of flammable gas or vapour was simply classified as a Class I location. Electrical equipment and wiring located in such areas had to meet the most stringent requirements that were approved at that time.
It was eventually agreed that there was a need to divide Class I into two divisions. It had become obvious that there were many situations where there was a minimal chance that gas or vapour would be present. In fact, it was not expected that gas or vapour would be present at all during normal working conditions, but it was recognized that an accident or other abnormal condition could result in a release of hazardous gas or vapour.
Locations in which the presence of gas or vapour was unlikely under normal situations, were classified Division 2, and were subject to less stringent requirements for equipment and wiring. All other Class I locations were classified Division 1 and continued to be subject to the more stringent requirements.
It should be noted that the principle behind the division of Class I locations is as significant as the actual practical application. Dividing Class I locations into two divisions introduced the principle of "probabilities.” In other words, when classifying hazardous locations it became acceptable to consider the probability, or likelihood, of gas or vapour being present simultaneously with a source of ignition.
Therefore, in the division system, Division 1 locations are those where the likelihood of explosive gas atmospheres occurring is the highest, and Division 2 locations are those where the likelihood is reduced. The Canadian Electrical Code defines Division 1 and 2 as follows:
(a) Division 1, comprising Class I locations in which:
(i) Hazardous concentrations of flammable gases or vapours exist continuously, intermittently, or periodically under normal operating conditions; or
(ii) Hazardous concentrations of flammable gases or vapours may exist frequently because of repair or maintenance operation or because of leakage.
(b) Division 2, comprising Class I locations in which:
(i) Flammable volatile liquids, flammable gases, or vapours are handled, processed, or used, but in which the liquids, gases, or vapours are normally confined within closed containers or closed systems from which they can escape only as a result of accidental rupture or breakdown of the containers or systems or the abnormal operation of the equipment by which the liquids or gases are handled, processed, or used; or
(ii) Explosive gas atmospheres are not likely to occur in normal operation and, if they do occur, they will exist for a short time only; or
(iii) Explosive gas atmospheres are normally prevented by adequate ventilation but which may occur as a result of failure or abnormal operation of the ventilation system; or
(iv) The location is adjacent to a Class I, Division 1 location, from which a hazardous concentration of gases or vapours could be communicated, unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.1
The Zone System
Just as the division system uses two divisions to describe the specifics of Class I locations, the zone system, first published in the CE Code in 1998, uses three zones. The zone system originated in the international community, in standards developed by standards development organizations such as the International Electrotechnical Commission (IEC) and CENELEC (the European standards writing body).
The following is an excerpt from the IEC Standard 60079-10 and explains the probability principle that is used in international standards. (It is interesting to note that the Canadian Electrical Code has followed this same principle in developing standards for equipment and wiring in hazardous locations since the implementation of the division system).
In most practical situations where flammable materials are used, it is difficult to insure that an explosive gas atmosphere will never occur. It may also be difficult to insure that apparatus will never give rise to a source of ignition. Therefore, in situations where an explosive gas atmosphere has a high likelihood of occurring, reliance is placed on using apparatus which has a low likelihood of creating a source of ignition. Conversely, where the likelihood of an explosive gas atmosphere occurring is reduced, apparatus constructed to a less rigorous standard may be used.”2
In the zone system, Zone 0 represents that area where there is the most likelihood of an explosive gas atmosphere being present, Zone 1 is that area where the likelihood is reduced somewhat, and Zone 2 is that area where the likelihood is reduced even further.
The Canadian Electrical Code Rule 18-006 defines Zones 0, 1, and 2 as follows:
(a) Zone 0, comprising Class I locations in which explosive gas atmospheres are present continuously or are present for long periods;
(b) Zone 1, comprising Class I locations in which:
(i) Explosive gas atmospheres are likely to occur in normal operation; or
(ii) Explosive gas atmospheres may exist frequently because of repair or maintenance operations or because of leakage; or
(iii) The location is adjacent to a Class I, Zone 0 location, from which explosive gas atmospheres could be communicated.
(c) Zone 2, comprising Class I locations in which:
(i) Explosive gas atmospheres are not likely to occur in normal operation and, if they do occur, they will exist for a short time only; or
(ii) Flammable volatile liquids, flammable gases, or vapours are handled, processed, or used, but in which liquids, gases, or vapours are normally confined within closed containers or closed systems from which they can escape only as a result of accidental rupture or breakdown of the containers or systems or the abnormal operation of the equipment by which the liquids or gases are handled, processed, or used; or
(iii) Explosive gas atmospheres are normally prevented by adequate ventilation but may occur as a result of failure or abnormal operation of the ventilation system; or
(iv) The location is adjacent to a Class I, Zone 1 location from which explosive gas atmospheres could be communicated, unless such communication is prevented by adequate positive-pressure ventilation from a source of clean air, and effective safeguards against ventilation failure are provided.3
The process of changing a two-division system to a three-zone system was simplified by the knowledge that the rather broad allocation of "”Division 1″” would be more specific when split into two parts. These two parts are relative to the frequency and duration of exposure to a release of gas or vapour, i.e.,
Areas having a high likelihood of release (continuous, long periods of time) match the definition of Zone 0.
Areas having a lower likelihood of release (expected but will not occur for long periods) match the definition of Zone 1
Division 2 became Zone 2
Impact on Section 18 (installation rules)
Rule 18-000 Scope
Because of the significance of the changes made to the CE Code, the scope had to be worded to make it clear that any new installation undertaken, subsequent to the adoption of the 1998 edition of the code, would be subject to the zone system of classification. Subrule (1) covers this by stating that Section 18 (which uses the zone system) applies to all locations classified as Class I.
At the same time, there had to be enough flexibility for those existing facilities, already classified to the division system, to continue to operate, expand, or be modified, without an enforced reclassification. As well, the rules related to the division system had to be kept up to date and be available for use with those facilities.
This was accomplished by expanding the Scope from the previous two subrules to the present five. The Scope now includes provisions for the continued use of the division system in specific cases (Subrule 18-000(3)), and mandates the division system rules, located in Appendix J, for those cases (Subrule 18-000(4)).
Rule 18-002 Terminology
There is some new terminology in Section 18 that is particularly important to the application of the zone system.
"Adequate Ventilation.”This term has never been defined in the CE Code prior to the 1998 edition. Adequate ventilation simply means ventilation, either natural or artificial, that is sufficient to prevent the accumulation of vapour/air or gas/air mixtures in concentrations above 25 percent of their lower explosive limit. Both artificial ventilation and natural ventilation are considered in this definition. In previous issues of the code natural ventilation was never a consideration.
"Degree of Protection”and"Methods of Protection.”These definitions appear to be related but the difference is quite significant and warrant some discussion.
Degree of protection signifies the degree to which equipment will prevent ingress of foreign bodies such as dust or liquids.
Methods of protection are the methods used in the manufacture of equipment to ensure that it does not become or provide a source of ignition. These terms will appear in several of the revised rules in this section.
"Explosive Gas Atmosphere.”This is defined as a mixture of gas or vapour and air that is within its flammable limits. The term simplifies the previous reference to "flammable gases or vapours which may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.”
"Normal Operation.”This term is used in much of the literature dealing with the zone system and has been defined as the situation when the plant or equipment is operating within its design parameters. An abnormal operation would result in a release of gas or vapour sufficient to develop an explosive gas atmosphere.
Methods of Protection
The division system uses the basic protection features of explosion-proof equipment, purged or pressurized equipment or intrinsically safe equipment. The zone system introduces a number of additional protective principles.
They are defined in the Canadian Electrical Code, so the following is intended as a paraphrase only. (Included in brackets after the name is the symbol that is used to identify each one.)
"Intrinsically Safe” (Intrinsic Safety i, ia, or ib).Intrinsic safety (i) is the intrinsic safety that has been part of the division system. The IEC standards have introduced two new classifications of intrinsically safe:
- Intrinsic safety (ia) provides the same level of protection as intrinsic safety (i) used in the previous edition of the code. During testing, it must continue to provide explosion protection after two countable faults have been applied (countable faults are faults to components of the equipment being tested, not field wiring components).
- Intrinsic safety (ib). Equipment certified with intrinsic safety (ib) does not have quite the same level of backup protection as (ia) or (i). During testing, it must continue to provide explosion protection after only one countable fault has been applied.
"Flameproof” (d).Flameproof equipment provides the same type of protection as explosion-proof. The principle of both is to contain an explosion within the enclosure. Hot gases cool as the increased pressure forces them out though an engineered flame path and will not ignite the surrounding hazardous atmosphere.
"Increased Safety” (e).Equipment which is considered approved under the increased safety standard will have:
- a high impact type of enclosure,
- protection against the ingress of dust and moisture,
- a high degree of safety in the terminals, i.e., splices will not be permitted in an increased safety enclosure, and
- improved tracking distances between terminations.
In general, an increased safety enclosure is one in which steps have been taken to increase the safety that is provided by the enclosure and the equipment that is inside. There will be no arc producing, heat producing or sparking apparatus enclosed in an increased safety enclosure.
The following four methods of protection use similar principles:
- "oil immersed” (o)
- "pressurized” (p)
- "powder filled” (q)
- "encapsulation” (m)
Because of the special type of manufacture, gas or vapour is excluded from contact with those parts of the equipment that produce arcs, sparks or high temperatures. Ignition will therefore not occur.
"Non-sparking” (n).This is a more generalized term and will cover many types of equipment. Basically, the equipment will not produce arcs, sparks, or high temperatures, and it is unlikely that a fault will occur within the equipment.
Refer to the Canadian Electrical Code, Appendix B notes, page 577 for further information, including the standard number, for each method of protection covered in the CAN/CSA – E79 series of standards.
Rule 18-050, Electrical Equipment
Standards governing the manufacture of equipment for use in hazardous locations have traditionally been part of the C22.2 or CAN/CSA C22.2 group of standards. When referring to equipment certified under these standards, the code has stated that equipment that is required to be approved for a class of location, i.e., Class I, must also be approved for the specific gas or vapour that will be present. To simplify this process, gases and vapours having similar properties are grouped together. Group designations used with the division system for Class I locations are Groups A, B, C, and D.
To take full advantage of the move to the zone system, new standards were required to cover the manufacture of equipment intended for Class I, Zone 0, 1, and 2 locations. Standards, based on the IEC standards, were developed and adopted under the CAN/CSA E79 series of standards. To follow the IEC standards as closely as possible, the IEC method of naming gas groups IIA, IIB, and IIC was also adopted.
It is critical to recognize that the gases contained in Group IIA do not correspond to those in Group A. Instead, Group IIA gases correspond to those in Group D. Similarly, Group IIB gases correspond to those in Group C, and Group IIC gases correspond to those in Groups A and B combined. This means greater attention needs to be paid to the marking on the equipment (i.e., is the equipment suitable for Group A or Group IIA gases?)
A complete listing of typical gases and vapours along with a cross reference between the two types of group names is shown in the Canadian Electrical Code Appendix
Rule 18-052 Marking
All electrical equipment must bear a certification mark such as the CSA mark, to confirm that the equipment has been certified, as required by Rule 2-024.
In addition, the marking convention for equipment intended for hazardous locations under the division system includes the class of location, gas group, and temperature or temperature code. A typical marking may be:
Class I, Group D, T4
The marking convention under the zone system includes the Ex or EEx mark to indicate that the equipment is explosion protected, the symbol for the method of protection (d, e, etc.), the gas group, and the temperature code. A typical marking may be:
Ex d IIA T4
The marking conventions between the division and zone systems are quite different and we can expect to see either one on equipment used in Class I hazardous locations. An important point is that the latter does not include the "”class of location”" and, therefore, equipment with this marking is not permitted in a Class I Division 1 location unless it has had the class of location added.
A table showing the types of equipment permitted and the methods of protection acceptable for use in the zone and division systems is given in the Canadian Electrical Code, Appendix J.
Rule 18-090 Equipment and Wiring in Class I Zone 0 Locations
While a Class I Division 1 location includes the area designated under the zone system as Zone 0, there is a difference between the two systems in the rules for electrical equipment and wiring.
Rules for Class I Division 1 locations include:
explosion-proof equipment and wiring,
equipment and wiring that is pressurized or purged with a protective gas (see Rule 18-002 Special Terminology), or
equipment approved as intrinsically safe and associated wiring that is designed and installed as intrinsically safe.
Rules for Class I Zone 0 locations require intrinsically safe equipment and wiring of the (i) or (ia) types only.
Rule 18-090 also includes the requirements for seals in conduit runs where they leave the Zone 0 location and in cable runs at the first termination in the Zone 0 location.
Rules 18-106 Wiring Methods Class I Zone I
Although the wiring methods for Class I Zone 1 locations are quite similar to those normally permitted in Class I Division I locations, Subrules 18-106(3), (4), and (5) indicate that there are some significant differences.
Subrules (3) and (4) cover the requirements for threaded joints. Subrule (3) permits the use of straight threads in equipment required to be explosion-proof or flameproof design (tapered threads must still be used on the conduit as required in Rule 12-1006). Subrule (4) covers the need for approved adapters in cases where the threads may be metric rather than the more commonly used National Pipe Thread (NPT).
Another point to consider in dealing with threaded joints in a hazardous location is the number of fully engaged threads that are required. With the division system, the requirement is for 5 fully engaged threads in any hazardous atmosphere. With equipment used in the zone system, 5 fully engaged threads are required in Group IIA or IIB atmospheres, but at least 8 fully engaged threads are required in a Group IIC atmosphere.
Subrule 18-106(5) covers the need for care when terminating conduit or cable in enclosures with the method of protection "”e”" (increased safety). Such entries are to maintain the degree of protection provided by the enclosure. The increased safety principle includes preventing the ingress of dust or moisture into the enclosure. When such an enclosure is installed in the field, steps must be taken to ensure that principle is not compromised.
Rule 18-108 Sealing, Class I, Zone 1
There are two basic differences in the rules for sealing brought about by the move to the zone system.
The type of enclosure that is permitted in a Class I Zone 1 location is significant. For instance, seals will not be required on cables terminating at enclosures with the method protection "e” when run within the zone. Also cables that leave a Zone 1 location will not require a seal providing the cable is greater than 10 m (32.8 ft) in length and there are no excess process or atmospheric pressures involved that may force gas or vapour through the cable.
The need to seal conduit entries into enclosures that are not required to be either explosion-proof or flameproof is another significant difference. There are two reasons for this: the need to ensure dust and moisture cannot enter an increased safety enclosure, and the need to ensure the integrity of an explosion-proof or flameproof wiring system (i.e., a wiring system intended to contain an explosion). A seal must be installed at the transition to a wiring system that is not required to be explosion-proof or flameproof.
Rule 18-156 and Rule 18-158 cover wiring methods and sealing for Zone 2 locations. Since a Class I Zone 2 location is considered equivalent to a Class I Division 2 location, there are no significant differences in either the type of equipment that is permitted, the wiring methods or the requirements for sealing.
1 Canadian Electrical Code – C22.1 – 02
2 CEI IEC Standard 79-10 (60079-10) Third edition, 1995-12
3 Canadian Electrical Code – C22.1 – 02
Read more by Ken McLennan
Posted By David Young,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
| Comments (0)
About fifteen years ago, on a beautiful Saturday in September, my then nine-year-old son and I had just finished a wonderful day of sailing. Five hours earlier, when we put in at a new boat ramp, there were very few cars with trailers in the parking lot because the stiff wind was scaring the power boaters away. When we arrived back at the ramp, the parking lot was almost full. As I pulled my boat out of the water, I had to park on the far side of the parking lot well away from the water. As I pulled into the parking space to down rig the mast, I noticed a power line between the front of my car and the adjacent roadway. The high voltage conductors seemed too low for their location adjacent to an area that the National Electrical Safety Code (NESC) would clearly define as an established boat ramp and associated rigging area.
Photo 1. The utility quickly replaced the poles with taller ones. Photo 1 shows the line before it was corrected.
As my son and I lowered the short mast of our day sailor well away from the power line, another family backed their 22-foot day sailor into the parking space next to ours. I asked the man the length of his mast. He replied twenty-nine feet as he and his wife and two children prepared to raise the mast. I identified myself as an engineer with an electric power company and called his attention to the high voltage power line directly above the stern of his sailboat. If he raised the mast, it would surely hit the phase conductor. He acknowledged the hazard and then got irritated at me because he now had to move the trailer.
The next day, I contacted the utility and inquired about the line. The utility was not aware of the new boat ramp. The clearances were fine for a line along a coastal road, but they were dangerous next to a boat ramp. The people who built the boat ramp had created the hazard when they did not contact the utility. The phase conductor was only 24 feet above the ground. The utility quickly replaced the poles with taller ones. Photo 1 shows the line before it was corrected. The NESC minimum clearance of conductors over boat ramps and associated rigging areas is a function of the minimum clearance over the adjacent water.
Photo 2. Photo 2 shows an example of an obstruction that would prevent the passage of a sailboat.
The minimum clearance of conductors over water is covered by Rule 232 (page 71) and rows 6 and 7 of Table 232-1 (page 78). An "unobstructed surface” is a body of water where there is no fixed bridge or other obstruction preventing large sailboat access from a larger body of water. The larger the surface area of the body of water, the higher the clearance. For rivers, streams and canals, the surface area shall be the largest surface area of any one-mile segment that includes the crossing (Footnote 19). If a river, stream or canal has an unobstructed connection to a larger body of water, the clearance shall be based upon the water surface area of the larger body of water. Photo 2 shows an example of an obstruction that would prevent the passage of a sailboat. In photo 2, the power line crossing is actually between two fixed bridges 500 feet apart. The water surface area is less than 20 acres and thus the minimum clearance over that body of water is only 20.5 feet for phase conductors up to 22 kV phase to ground. If the body of water on the power line side of the bridge was directly connected without obstruction to the ocean, then the minimum clearance becomes 40.5 feet for phase conductors up to 22 kV to ground. Drawbridges are not considered obstructions. For bodies of water where the water level is controlled, the surface area and corresponding clearance shall be based upon the design high water level (Footnote 17). For bodies of water where the water level is not controlled, the surface area shall be that enclosed by its annual high-water mark. The clearance shall be based upon the normal flood level. If available, the 10-year flood level may be assumed as the normal flood level (Footnote 18). Note that some utilities have run into problems crossing shallow streams that become deep rivers at flood level. During storms, people out in sailboats often go up rivers to find a safe haven to weather the storm. Let us hope that they don’t find out in a flash that it wasn’t the safest move.
For boat ramps and associated rigging areas, the minimum clearance is specified in Rule 232 and in row 8 of Table 232-1 to be five feet greater than that specified over water in row 7. For the ramp and rigging area I spoke of previously, the minimum clearance for a 25 kV line (14,400-volt phase to ground) is 45.5 feet since the body of water next to the ramp is a river connected to the Atlantic Ocean.
The minimum clearances shall be met when the conductor is under maximum sag conditions. The three conditions that can create maximum sag conditions are spelled out in Rule 232A1, 2, and 3. The clearance shall be met with the conductor temperature of 120°F. If the crossing is designed for a maximum operating temperature exceeding 120°F; the clearance shall be met at the maximum operating temperature. In the medium and heavy loading districts, the clearance shall also be met when the conductor is at 32°F, with radial thickness of ice as specified in Rule 250B for the district.
National Electrical Safety Code® and NESC® are registered trademarks of the Institute of Electrical and Electronics Engineers.
Read more by David Young
Posted By Leslie Stoch,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
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This article looks at effective grounding and bonding, how it is defined by the code, and its importance to electrical safety.
The Canadian Electrical Code, Rule 10-500 Effective Grounding defines and specifies that: "The path to ground from circuits, equipment or conductor enclosures shall be permanent and continuous, and shall have ample ampacity to conduct safely any currents likely to be imposed on it, and shall have impedance sufficiently low to limit the voltage above ground, and to facilitate the operation of the overcurrent devices in the circuit.”
Appendix B offers some additional guidance by specifying that the impedance of the circuit fault return path must be sufficiently low so as to ensure that the overcurrent protection trips when it should to limit voltages on exposed metal and to permit minimum 5 x rated current to flow during a ground fault. "Rated current” is considered to be the rating of protection ahead in the circuit.
This article reviews several possible ground-fault return paths— the effective ones and the not so effective ones. When required, the Canadian Electrical Code requires that bonding conductors be installed in the same cable or raceways as circuit conductors. How important is that requirement and how critical is conductor spacing? The code does not specify any restrictions on the lengths of metal conduit or EMT when used as the equipment bonding means. Can metal raceways provide an equally effective fault path without any restrictions as to maximum length?
Let’s start with bonding conductor spacing. Tests have shown that bonding conductors must be close and parallel to the circuit conductors for the lowest impedance path for ground-fault currents. Inductive reactance increases with the distance between the circuit and bonding conductors and increases total impedance in the fault current return path. Inductive reactance always forces more current to flow along the paths closest to the circuit conductors.
Tests also show that the most effective fault return paths are bonding conductors inside cables or raceways, or metal conduit enclosing circuit conductors. Ineffective fault current paths are connections to grounded (or ungrounded) building steel, and bonding conductors external to raceways or cables. Also, due to its method of construction, metallic cable armour presents a higher impedance than metallic sheaths.
It can easily be demonstrated by testing that only an internal bonding conductor can divert a sizable amount of fault current from a metal raceway (approximately a 50-50 division). None of the other possible paths (building steel or external bonding) will have any appreciable effect on the direction of current flow.
The Canadian Electrical Code specifies no maximum length restrictions when metal raceway is used for equipment bonding. The cross-sectional area of a metal raceway is considered adequate to carry the available fault currents when selected in compliance with Tables 6 to 10. But is this enough?
The total circuit impedance of metal raceway consists of the raceway impedance, the couplings and the arc fault impedance. To determine the maximum length of metal conduit when used for equipment bonding, we must know:
- The minimum permissible ground-fault current (for effective grounding— at least 5 x the circuit overcurrent protection setting)
- The conduit impedance (from manufacturer’s data)
- The arc voltage (assume 50 volts)
- And allow a 50% margin of safety
Example – To calculate maximum ground fault impedance, for a 120/208-volt, 400-ampere circuit, assume a minimum fault level of 400 x 5 = 2000 amperes. Subtract the assumed arc voltage and divide by 2000 amperes.
120 – 50 volts = .035 ohms maximum
Next, find the conduit impedance at 2000 amperes per 100 feet (from wire and cable manufacturer’s data), apply a 50 percent safety factor and divide the permissible ground-fault return path (in this example .035 ohms) impedance by conduit impedance with safety factor to obtain the maximum permissible length of conduit. Although the Canadian Electrical Code does not specify it, maximum length is required by implication by Rule 10-500.
Based on the circuit protection rating, minimum bonding conductor sizes are selected from Table 16, but as a rule of thumb, they should have no less ampacity than 25 percent of overcurrent protection ratings. Bonding conductors must carry available fault currents during the clearing times of fuses or circuit breakers without any damage to wiring insulation, and without any risk of burning off.
Manufacturers can provide damage curve tables showing how much fault current and the lengths of time during which different size wiring can withstand faults without damage. Burn off tables are also available to show the melting points of copper and aluminum conductors at different fault currents and protection clearing times.
As mentioned above, distances between bonding and circuit conductors will affect bonding conductor impedance and resulting voltage drop during a ground fault. A higher impedance creates an increased risk of electric shock due to contact with exposed metal parts.
As in the past, you should check with the electrical inspection authority in each province or territory as applicable for a more precise interpretation of any of the above.
Read more by Leslie Stoch
Posted By James W. Carpenter,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
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Many questions have arisen since the announcement that the IAEI Board of Directors, recognizing the need for additional revenue, voted to increase the dues to $90.00 per year effective January 1, 2003.
Let us review what the purpose and objectives of the International Association of Electrical Inspectors are. Our founders, some 75 years ago, saw the need for an organization that could represent the electrical inspector in the national and international arena. In fashioning the Articles of Association they set forth in Article II, Section 1 the details of what the objectives of the IAEI shall be.
(a) To cooperate in the formulation of standards for the safe installation and use of electrical materials, devices and appliances.
(b) To promote the uniform understanding and application of the National Electrical Code and other electrical codes.
(c) To promote cooperation between inspectors, the electrical industry and the public.
(d) To collect and disseminate information relative to the safe use of electricity.
(e) To represent the Electrical Inspectors in all matters which are dealt with nationally and internationally by the electrical industry.
(f) To cooperate with other national and international organizations in furthering the development of the electrical industry.
Back 75 years ago the emphasis was on the national scene but today, in 2003, the scene is moving globally.
What do these objectives mean to the local one-person inspection department in small town America or the largest municipality? Why does the inspector need to belong to an international organization? What does the inspector member or the associate member get for $90.00 a year?
The IAEI sponsors two members, a principal and an alternate, on each of the nineteen NEC code making panels, and a principal and an alternate on the Technical Correlating Committee. The IAEI also has members on other standards making panels. This is done to fulfill the first objective to cooperate in the formation of standards. Even though the members are volunteering their time to do this important work of assuring that the inspectors’ voice and viewpoint is presented in the standards making process, the IAEI finances the travel, lodging, and meals of these 40 plus people. This happens on a three-year cycle so funds must be available for the ROP and ROC meetings. Even the smallest building in the most remote location must have a safe electrical installation and use safe electrical materials, devices, and appliances. The IAEI objective of cooperating in the formation of recognized standards IS important to every citizen living or working where electricity is used.
To promote the uniform understanding of electrical codes and standards, the IAEI produces publications on various aspects of the electrical code. These publications are on such timely code subjects as grounding, wiring of one- and two-family dwellings, and analysis of changes of the NEC. These books are priced to defray the cost of production and to return some extra funds to the association but printing must be paid for up-front. The IAEI decided to make these books available in the year that the NEC came out instead of spreading the production out over three years. The IAEI has an outstanding and hardworking staff writing material for the various books but they can’t do it all, so others are contracted to help write—another expense.
The Education Department is also producing and conducting seminars on a variety of timely subjects. The IAEI provides these educational experiences in many different ways. We conduct on-site seminars using our staff as instructors or contract with others to provide the instruction. We can partner with local chapters or divisions to conduct seminars, and we make available materials for chapters and divisions to conduct their own seminars.
The Education Department and the Publication Department combine to collect information (Education Department) and disseminate information (Publication Department) on the safe installation and use of electricity. Our representatives on code panels provide valuable information and insight on the code changes that is used by the Education Department to compose the text for the books. The Publication Department does an excellent job of editing and laying out the text and illustrations to produce an award-winning IAEI News and other technical books. This work does not just happen. Talented people are necessary and proper support in the form of advanced computers and software is required.
To represent the electrical inspector in the national and international arena and to cooperate with national and international organizations, the IAEI joins with others on the United States National Committee to represent the U.S. on the International Electrotechnical Commission (IEC).
Of course all this requires a support staff in the Customer Service Department. With the turn-over in customer service personnel, we have had problems with errors with our database. This seems to be what most people notice first about the association. We must do something to keep staff longer so they will be more sensitive to the members’ needs and realize what it means when errors are made.
Other things are needed to support the carrying out of the objectives. We have an office building that we must keep up to protect the investment— new roof, maintenance, taxes, and utilities. Also legal fees are incurred to protect our intellectual properties and to keep us out of trouble in contracts and agreements we enter into with other parties.
When all things are considered, I believe when one stops and reflects on them, one can see that a $90.00 membership fee to belong and support the IAEI is still "The Best Bang for the Buck.” I also believe that you only get out of anything, what you put into it. So take advantage of Section, Chapter and Divisions meetings. Participate in the education programs provided or better yet share your knowledge with others through the IAEI!
Read more by James W. Carpenter
Posted By Underwriters Laboratories,
Saturday, March 01, 2003
Updated: Thursday, February 14, 2013
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Question: Light curtains on industrial machinery
Does UL List light curtains that are used on industrial machinery to prevent personal injury?
Yes, light curtains are Listed under the category Active Opto-Electronic Protective Devices (NIPF), located on Page 60 of the 2002 General Information for Electrical Equipment Directory (White Book).
In January 2002 UL published new standards for Electro-Sensitive Protective Equipment, UL/ ANSI 61496-1 and 61496-2. UL 61496-1 contains general requirements and tests for all Electro-Sensitive Protective Equipment; UL 61496-2 contains specific requirements for Active Opto-Electronic Protective Devices, otherwise known as light curtains.
Light curtains are commonly used in industrial settings for the safeguarding of machinery that presents risk of personal injury. Light curtains typically consist of an emitter/ receiver pair. The length of the light curtain, number of light beams and spacing of light beams may vary depending upon customer application. When one or more beams of light are broken, due to for instance a hand in a point of hazard zone, within milliseconds a signal is sent to shut down machine operation. Signal redundancy and continuous selfchecking are among the requirements for light curtains.
In addition to an evaluation for fire and electric shock hazards, light curtains undergo a stringent investigation of their safety-related performance features. This includes evaluations of software reliability, Failure Mode and Effect Analysis (FMEA), EMC immunity, and resistance to mechanical and environmental stresses.
Question: USE and USE-2
Are Type USE and USE-2 suitable for exposure to sunlight?
All UL Listed service entrance cables are required to be sunlight resistant as part of their UL Listing. Both the cable assembly and the individual inner conductors are sunlight resistant, and neither is required to be marked. This information is noted in the UL Guide Information for Service Entrance Cable (TYLZ) located on page 104 of the 2002 White Book.
As a side note, individual insulated conductors, such as THWN, that are not part of a service entrance cable assembly are not sunlight resistant, unless so marked, (i.e., "sunlight resistant”).
Question: Electric sign
Does each individual part of an electric sign require a "Section ____ of _____” marking?
A UL Listed sign may be shipped in sections only when the sections form a complete sign and complete instructions for field assembly are provided. Each major subassembly is required to bear an electric sign section marking.
For example, separate channel letters and remote neon power supplies are considered major subassemblies and each subassembly requires a section marking. Sign faces, trim and mounting hardware are not considered major subassemblies.
The "section” UL Label has changed. The UL Guide information was revised to require each section to bear an "Electric Sign Section” Listing Mark in lieu of the "Section _____ of _____” marking where each section of the sign was assigned a number. The Electric Sign "Section _____ of ______” Listing Mark is still acceptable until the stock is depleted.
Electric signs are Listed under the category, "Signs” (UXYT). The UL Guide Information can be found on page 105 of the 2002 White Book or visit the UL Online Certification Database atwww.ul.com/database.
Question: Shower lights
Are lights installed in showers required to have GFCIs?
UL Listed luminaries are evaluated for compliance with the Standard for Luminaires, UL 1598. The UL Standard does not require integral GFCI protection for luminaries. If the manufacturer’s installation instructions require GFCI protection in the installation, then Section 110.3(B) of the NEC would be applicable. Also note that for some special occupancies in Chapter 5, the NEC requires GFCI protection to be provided for the equipment in the installation. The UL Guide Information for luminaires (IETX) can be found on page 40 of the 2002 General Information for Electrical Equipment Directory (White Book).
It is important to note that combination ceiling-insert exhaust fan/lights are Listed under the product category Electric Fans (GPWV) and are required by the Standard for Electric Fans, UL 507, to be marked, "Acceptable for use over a bathtub or shower when installed in a GFCI protected branch circuit.” This information is detailed in the Guide Information for this category located on page 203 of the 2002 White Book. In this case, the UL Standard does not require integral GFCI protection in the product. However, the product must be marked to indicate that a GFCI protected branch circuit should be used to supply power to the product. Section 110.3(B) of the NEC is applicable.
Question: Listing mark on outlet box
Why isn’t the UL Listing Mark always required on an outlet box? I’ve seen the Mark on packaging, but once it’s discarded, it is difficult to verify Listing.
For some products, the UL Mark is on the smallest unit container. This is due to the size and/or shape of the products, which physically does not allow the UL Mark on the product itself. For outlet boxes, the UL Listing Mark is required on the product, or the UL symbol can be marked on the product and the complete Listing Mark of Underwriters Laboratories Inc. is marked on the smallest unit container. This practice has been in place for many years. This information is detailed in the UL Guide information for "Metallic Outlet Boxes” (QCIT) located on page 81 of the 2002 General Information for Electrical Equipment Directory (White Book).
For all UL Listed or Classified products, the Guide Information for each product category contains a description of how the product is to be marked to identify that the product is UL Listed or Classified under that product category.
UL Question Corner
Posted By Brian Haydon,
Wednesday, January 01, 2003
Updated: Thursday, February 14, 2013
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In Canada, CSA is one of four nationally accredited Standard Development Organizations (SDO) and publishes Canada’s electrical code and electrical product standards.
The Canadian Electrical Code (CE Code) is the governing electrical code for the majority of Canada, and consists of two parts. The CE Code, Part I establishes requirements for electrical work and the installation of electrical equipment operating or intending to operate at all voltages in electrical installations for buildings, structures and premises across Canada. The 2002 CE Code, Part I is the 19th edition of the code, and was first published in 1927.
Requirements for electrical equipment are included in a list of more than 500 individual product standards, collectively referred to as the CSA CE Code, Part II. CSA Part II electrical equipment standards include product specifications, test methods, design requirements, classifications, recommended practices and other requirements to which electrical products are certified in order to bear the appropriate certification mark in Canada.
Standards are living documents, continually revised and refreshed to address changing requirements and emerging technologies. Standards are reviewed at least every five years as part of this process of continual improvement.
Accreditation of a Standards Development Organization (SDO) is the formal recognition of their competence to develop standards, and comply with specific accreditation criteria as determined by the accreditor.
The Standards Council of Canada (SCC), a division of Industry Canada, a Federal Crown Corporation, has responsibility for co-ordination of the National Standards System (NSS) in Canada. To achieve and maintain accreditation, a SDO must adhere to the principles governing the consensus process used in Canada for the development of consensus standards. This includes, but is not limited to, undergoing a public review process and not being framed in such a way that it will act as a restraint to trade. Further, standards should be consistent with or incorporate appropriate international standards as well as pertinent national standards.
Anyone can come forward and request a standard. Often it is a consumer organization, trade/industry association or a government department, which has observed a need. The SDO then evaluates the usefulness of a potential standard in meeting the need and assesses the level of support in the community and industry.
In the standards development process, the SDO functions as a neutral third party, providing a structure and a forum for developing the standard. Standards are developed using committees created using a "”balanced matrix”" approach. This means that each committee is structured to capitalize on the combined strengths and expertise of its members— with no single interest group dominating. In CSA’s development process, under which the CE Code, Parts I and II are developed, committees are divided into distinct interest groups including producers, regulatory authorities, end users and general interest.
The standards development process requires the technical committee to consider the views of all participants and develop the details of the standard by a consensus process, which includes the principles of inclusive participation, and respect for diverse interest and transparency. Substantial agreement among committee members, rather than a simple majority of votes, is necessary. When a draft standard has been agreed upon, it is submitted for public review, and amended if necessary.
The CE Code, Parts I and II, as well as all other standards facilitated by CSA, are developed by sub-committees and technical committees, consisting of recognized experts, who volunteer their time, resources and efforts to the standards development process.
Input on changes and maintenance of the CE Code Part I come from forty-two subcommittees each representing a section of the CE Code Part I. Using a similar process, over five hundred CE Code Part II product standards have been developed and maintained over the last 70 years. The present committee hierarchy includes five CSA technical committees, supported by 224 CSA technical subcommittees with over 1,200 voluntary members.
In accordance with the National Standards System, a consensus development process is followed to create and maintain CSA Part II electrical equipment standards. This process is used in the development of new standards, amendments to standards or new editions. Because of the immense size and scope of the CE Code Part II, each standard is identified as a project, with a schedule established and monitored by a CSA-assigned project manager. Time to completion is dependent on member commitment to the task, available resources, and the need to move the project through defined stages of development. The flow, followed for each project, is shown in the following diagram.
The complete process is described in eight stages.
To begin, a request for the development of a new standard, new edition or amendment, may come from any interested person, organization or committee. At the preliminary stage, an evaluation is conducted and the project submitted for authorization. The evaluation determines if the product and process selected, for example, an amendment versus a new edition, will be an appropriate solution to the problem. In addition, the result must have value for the stakeholders, and the result must be achievable. After a defined evaluation process, a decision is reached on whether the project can proceed.
Organizations, industries, regulatory authorities, etc., that have been identified as having an interest in the project are requested to participate. To complement this, a public notice of intent is made to improve input early in the process. This provides unidentified stakeholders the opportunity to request to participate, to offer comments, or keep abreast of the progress of a project.
Assignment of the project to an appropriate CSA Technical Committee (TC) is made at this stage. For the CSA electrical program, the six established CSA TCs are Wiring Products, Industrial Products, Consumer and Commercial Products, General Requirements, International Standards, and Fuel Cell Technologies. Each TC receives strategic leadership from the Strategic Resource Group (SRG), a steering committee for electrical standards development, and policy direction from the Standards Policy Board (SPB). The SPB, SRG and TC(s) committees are balanced, with voting members maintained within a minimum and maximum range, in defined categories, for example, regulatory, manufacturer and general interests. Each TC may assign detailed technical work to a Technical Subcommittee (TSC), while maintaining responsibility for formal approval of a standards technical content.
In the preparatory stage, the items considered are harmonization, copyright, resources to develop a working draft, and the project schedule.
Harmonization:A recommendation on harmonization may occur at an earlier stage. This issue is now given full consideration. First preference is to harmonize with an international standard. For products in the electrical field, an IEC standard may be adopted. Minor technical deviations from the original IEC standard are allowed to satisfy Canadian needs. These may include unique conditions such as environment, government regulation, the electrical installation code, or industry practice.
Second preference, when not feasible or appropriate to harmonize with an international standard, is the development of a regional standard. This is a joint standard, typically tri-national or bi-national, formally approved and published by CSA and the SDO of one or more other countries. The CANENA (a Spanish acronym for Council for Harmonization of Electrotechnical Standards of the Nations of Americas) forum has been established in North America to facilitate the harmonization of standards and promote the reduction of non-tariff trade barriers for electrotechnical products between Canada, Mexico, and the United States of America. Currently, there are over 40 CANENA Technical Harmonization Committees. Their role is to help facilitate the development of harmonized seed documents for consideration by each country and its participating SDO. In August 2000, the first tri-national harmonized series of standards in the electrical sector, CSA C22.2 No. 248.1 – 248.16 (Low-Voltage Fuses) was published by the participating SDOs and is recognized in all three countries. Currently, CSA has published 25 bi- and tri-national electrical standards where the harmonized seed document was developed within the CANENA forum.
Third and least used for electrical products, a national standard unique to Canada would be established, where no standard exists elsewhere.
Copyright:At stage 2, copyright issues are addressed. The Standards Council of Canada has been granted copyright control within Canada for standards of the IEC. In turn, the Standards Council of Canada can permit these rights to be used by CSA for developing National Standards of Canada. A National Standard of Canada (NSC) is a consensus standard prepared by an accredited standards-development organization and where the development process has been approved by the Standards Council of Canada.
For regional standards, an existing standard from another standards-development organization may be used as a start point. For such material, copyright agreements are established or reaffirmed at this stage.
Resources:With the aid of a CSA-assigned project manager, preparation of a working draft can now begin in accordance with CSA Directives and guidelines through the TC, a subsidiary committee(s), or a single technical expert. A subsidiary committee may be a task force, or as indicated earlier, a technical subcommittee (TSC).
Project schedule:CSA staff, in consultation with the TC, establish target dates for key milestones, including public and internal review, TC approval, final edit, and publication. A schedule is formed at this stage to ensure the availability, on a timely basis, of needed resources to advance the project.
The committee stage involves the development of technical content of a draft. CSA technical subcommittees for specific electrical product sectors are well established, providing balanced expertise to prepare a draft on a consensus basis. For regional electrical standards, a CANENA technical harmonization committee (THC) may prepare the draft, prior to review by a CSA TSC or TC. The THC typically will include selected members from the corresponding CSA TSC, as well as technical experts from the other participating countries.
The technical content of a draft is developed at meetings (either in person or by video/teleconference), by correspondence, or by electronic means. Internet-based meeting methods are now appearing, providing a combination of teleconferencing with PC-based Internet access to the draft under development. Using this method, committee members can provide input, without the necessity of travel, while one person controls and updates the draft in real time.
During development, consideration is given to corresponding international activity, including relevant international documents and the work of the Canadian Subcommittee for IEC, where one exists. In the electrical safety sector, integration of CSA technical subcommittees with Standards Council of Canada, Canadian Subcommittees to the IEC is a current initiative underway at CSA.
All decisions regarding technical content are determined by consensus. Consensus on the technical content, which is the responsibility of the TC, is confirmed by letter ballot or recorded vote.
At this stage, the draft is offered to the public for review and comment. The comments are then passed on to the appropriate committee for consideration, and if the draft is subsequently revised, the draft is re-circulated to the committee.
An internal review of the draft by CSA staff verifies compliance with CSA policy, format and editorial style. This is to ensure that all users of the standard will be able to reach a common understanding of its contents.
First phase:The TC approves the technical content by letter ballot or recorded vote. The criterion for approval asks the questions, are the technical requirements reasonable and justifiable considering the state of the art in the particular field? Does the draft meet the defined need, and is the scope of the draft consistent with the technical requirements included?
For approval, defined numerical requirements for voting must be met, negative votes must be suitably dispositioned, and comments must be considered.
Second phase:In the first phase, the approval of technical content by the TC is final. The second phase, Second Level Review, is a strict procedural review by an internal CSA committee to verify that all required steps during development have occurred in accordance with CSA Directives and guidelines.
Completion of the previous stage is a prerequisite to proceeding with publication. When this stage is reached, a final edit by CSA staff verifies conformance with applicable editorial requirements. Then the standard is published. CSA Part II electrical equipment standards are available in a number of formats, including hard-copy text, PDF files (on-line) and CD-ROM.
The final standard may be voluntarily adopted for use, or may be referenced in legislation. Additionally, if in compliance with Standards Council of Canada requirements, CSA is authorized to publish the standard as a National Standard of Canada.
The standard is maintained with the objective of keeping it up-to-date and technically valid. The same consensus development process as defined earlier, if required, develops amendments or new editions. A systematic (five-year) review of all CSA Part II standards is made, and reaffirmed as written, or a new edition, if appropriate, is produced.CSA CE Code, Part II standards provide the product requirements for certification of electrical equipment in Canada. Only products bearing one of the marks or labels applicable for Canada, from an accredited certification organization are normally considered approved by Canadian regulators, within their authority and jurisdiction to approve electrical products.
For harmonized standards that are regional or international, national differences applicable strictly to Canada, if any, appear within the Part II standard. Products bearing one of the marks or labels, applicable for Canada, indicate approval for use in Canada through compliance with the Part II standard, and must include compliance with any requirements for national differences for Canada.
CSA International, a division of CSA Group that offers global conformity assessment services, is an OSHA-accredited testing laboratory in the United States. Electrical inspectors accept products certified by CSA International to U.S. standards if they are adorned with the CSA/US certification mark.
In summary, for Canada a list of CSA Canadian Electrical Code, Part II, Safety Standards for Electrical Equipment appears in Appendix A of the CSA Canadian Electrical Code, Part I. Each of these electrical equipment standards have been developed and maintained, using CSA’s consensus standards development process.
Read more by Brian Haydon
Posted By George Gregory,
Wednesday, January 01, 2003
Updated: Thursday, February 14, 2013
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Arc-fault circuit interrupters (AFCIs) have just become required for installation in residences under the 2002National Electrical Code(NEC). Not surprisingly, questions have been raised regarding their application and even the need for them. There have been marketing pitches, technical opinions and, quite frankly, intentional misinformation floating around various industry channels. The intent of this article is to bring out the truth about what AFCIs are and what they are not.
This is Part I of a two-part article produced to directly address some of the questions and the misinformation about AFCIs. Part I focuses on the technology, the AFCI product standard and what the NEC is written to accept. Part II will focus on questions related to application and installation in accordance with the NEC.
Contrary to popular belief, AFCIs are not "new.” They are certainly in their infancy relative to many products, but they are not new. Square D began research in this area in the late 1980s and early 1990s; at about the same time the Consumer Product Safety Commission identified a concern with residential fires of electrical origin. A large number of these fires were identified to be in the branch-circuit wiring system.
The need for AFCIs became more apparent as the Electronic Industries Association (EIA) initiated a project and ultimately code proposals to the 1993 NEC to change the instantaneous trip levels of 15 and 20 A circuit breakers. EIA had studied the issue of arcing fires and determined that some level of additional protection from effects of arcing faults would be beneficial. EIA attempted to improve protection by requiring that the instantaneous trip level of a circuit breaker be reduced to the 85 A level. However, it became clear that lowering the instantaneous levels below the minimums already in the market would result in nuisance operation of the circuit breaker due to inrush currents.
The CPSC study and the EIA efforts led to the first proposals to require AFCIs during the revision cycle to create the 1999 NEC.
Figure 1. 210.12, Arc-fault Circuit-Interrupter Protection
NEC Code-making Panel 2 (CMP-2) was presented with numerous proposals ranging from protection of basically all 15- and 20-A circuits in dwelling units to protection of living and sleeping areas. After listening to many presentations, reviewing large amounts of data, conducting extensive discussions and giving consideration to the issues, CMP-2 concluded that AFCI protection should be required for branch circuits that supply receptacle outlets in bedrooms. The panel placed an effective date of January 1, 2002, for the requirement to become effective. CMP-2 members unanimously passed this action. Subsequently, the requirement was retained in the 2002 NEC with enhancements.
The Need for Arc-Fault Protection
Just as we only need a smoke alarm or a circuit breaker when a problem occurs, we also only need AFCI protection when a problem occurs—then we really need it. A fuse or circuit breaker cannot detect hazardous arcing current that is below its time-current opening characteristic. Arcing faults are frequently below the characteristic. The data on fire origin shows the need for this protection.
A recent report by the National Association of State Fire Marshals states:
According to the National Fire Protection Association and the National Fire Incident Reporting Sys- tem data, during the five-year period from 1994- 1998, there were an average of 73,500 total electrical fires annually, which were responsible for 591 Deaths, 2,247 injuries, and property damage totaling $1,047,900,000. The electrical problems that lead to these fires went undetected by conventional circuit breakers. Of these 73,500 electrical fires, 60,900 or 82% were caused by arcing and not by overloads or short circuits. 1
It may not be realistic to expect AFCIs to detect 82 percent of the conditions that cause fires from electricity and the cited report does not expect that. However, the conclusion indicates the high percentage of cases in which at least one authoritative source finds arcs to be a fire cause worthy of attacking. The AFCI does just that and does it effectively.
AFCIs address a real cause of home fires. Below is a list of reported incidents in which AFCIs detected arcing conditions that could have developed into fire causes.
- An appliance plug damaged by impact repeatedly caused tripping of the AFCI until the problem was discovered. When the appliance cord was replaced, no further tripping of the AFCI occurred.
- A room air conditioner that had developed a defect tripped the AFCI. The performance of the AFCI was questioned until the offending appliance was discovered and disconnected. The AFCI continues in service with no further tripping.
- An AFCI installed in a new building tripped repeatedly until damage caused by a nail through insulation was discovered and corrected.
- An AFCI installed as a retrofit in an older building tripped as soon as it was turned on. The installing electrician found the problem with extensive evidence of arcing in an old lighting fixture.
- Another damaged lamp with line-to-ground arcing was found when an AFCI was installed in an existing circuit. The AFCI tripped when the circuit was first energized after the installation.
- An AFCI tripped when retrofitted into an existing circuit. Examination of the circuit disclosed that wire insulation had burnt back exposing bare conductors near their connection to a receptacle. The exposed wires had been arcing through the charred insulation. It appeared that heat from a loose connection at the receptacle had caused the wires to burn back.
Table 1. Table 1 briefly compares the capabilities of the three types plus the outlet branch circuit AFCI.
As you might guess from that list, the greatest number of fires from electrical causes is in homes ten years old and older where changes have been made to electrical circuits by various owners and where insulation is deteriorating with age, use and misuse. However, fires from electrical arcs are recorded for residences of all ages. Besides, all homes become older homes. If the protection is not present before they age, they will remain unprotected as they age.
NEC 210.12 Requirement
NEC 210.12 defines an AFCI as "a device intended to provide protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.” The AFCI has two basic functions, which are recognizing arc characteristics and de-energizing the circuit when it recognizes them. There is no protection unless the source of voltage is disconnected from the hazard, once the hazard is detected.
The requirement of 210.12(B) states, "All branch circuits that supply 125-volt, single-phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter listed to provide protection of the entire branch circuit.”
This requirement in the 2002 NEC reads the same as that in 1999, except for two points. First, "outlets” read "receptacle outlets” in 1999. The change indicates that CMP-2 intended that all fixed wiring be protected. The protection extends also to extension and appliance cords. Second, the word "entire” is added, again indicating the intention to protect the fixed wiring of the entire branch circuit.
The only devices covered by the UL 1699 Standard for Arc-fault Circuit Interrupters that also satisfy these NEC requirements are the branch/feeder and combination AFCIs, when they are installed at the source of the branch. The branch/feeder AFCI is the circuit-breaker type that has been the topic of discussion since the AFCI was first proposed for the 1999 NEC. Branch/feeder AFCIs are listed by at least four manufacturers and are readily available. A combination AFCI has not yet appeared commercially, but at least two manufacturers have mentioned development of them.
There are six devices covered in UL 1699, three of which are defined there as follows:
Branch/feeder AFCI — A device intended to be installed at the origin of a branch circuit or feeder, such as at a panelboard. It is intended to provide protection of the branch-circuit wiring, feeder wiring, or both, against unwanted effects of arcing. This device also provides limited protection to branch-circuit extension wiring. It may be a circuit-breaker type device or a device in its own enclosure mounted at or near a panelboard.
Outlet circuit AFCI — A device intended to be installed at a branch-circuit outlet, such as at an outlet box. It is intended to provide protection of cord sets and power-supply cords connected to it (when provided with receptacle outlets) against the unwanted effects of arcing. This device may provide feed-through protection of the cord sets and power-supply cords connected to downstream receptacles.
Combination AFCI — An AFCI which complies with the requirements for both branch/feeder and outlet circuit AFCIs. It is intended to protect downstream branch-circuit wiring and cord sets and power-supply cords.
Definitions of the cord or portable AFCIs or the leakage-current detector-interrupter are not provided here because they are for specialized applications and are not intended for general protection of branch circuits.
Table 1 briefly compares the capabilities of the three types plus the outlet branch circuit AFCI.
This table, together with the definitions, is intended to help clarify the differences between these three types. So far, only the branch/feeder AFCI has been offered commercially, to the knowledge of the authors. It is the commonly available AFCI in circuit-breaker form. The outlet circuit AFCI is intended for protection of extension and appliance cords. It could also be produced in "feed through” form to protect fixed wiring on its load side. Located at a receptacle outlet, it would not protect the entire branch and would not satisfy the NEC 210.12 requirement.
The combination AFCI is intended to combine the performance of the other two in a single device. Its location is not specified in the definition; however, it can be configured in a form, such as in a circuit breaker, to be located such that it will protect the entire branch circuit, including fixed wiring plus extension and appliance cords in accordance with the UL 1699 Standard.
Branch/feeder AFCI Performance
One of the major reasons for development of AFCI technology is that a number of fires are caused by arcing short circuits in fixed wiring that are not detected by an overcurrent protective device before the fire starts. An overcurrent protective device (a circuit breaker or fuse) has an intentional time delay to allow for elevated current such as would be experienced when operating a microwave oven or starting a vacuum cleaner motor. In other words, when starting a vacuum cleaner, the elevated current is essential and is contained within the conductors. When the current is an arc, it is causing damage continuously. The AFCI distinguishes between the hazardous arc and normal current flow.
As discussions of a standard began in 1994, a rough but scientific experiment was conducted to determine the time and current within which an arc will ignite tissue paper. It was found that arcs above 5 amperes were likely to cause fire ignition if they persisted for a second and those below 5 amperes were much less likely to cause fire. Since then, other experiments have been conducted that suggest that fire can be ignited with lower current levels, but none have been definitive.
The branch/feeder AFCI was the first type to be developed. The intention was to protect branch-circuit wiring primarily and to also provide protection for extension and appliance wiring to the extent it could. The 5-ampere level was found to be difficult to achieve in line-to-neutral arcing at the time AFCIs were first developed, since it is essential to also avoid nuisance operation for the broad range of signals in electrical circuits. In any general-use branch circuit, a variety of dimmers, computers, motors, entertainment appliances and other equipment that produce arcs as part of normal operation may be installed or connected. The 5-ampere detection requirement was set for series arcs that include arcing to grounded conductors.
The 75-ampere level was taken from a survey conducted by UL for the EIA that reported that the lowest short circuit level available at a receptacle within the United States is 75 amperes. This means that a line-to-neutral fault in a branch circuit will have 75 amperes or more available. Correspondingly, AFCI testing verifies that the AFCI will detect an arc in a circuit with 75 amperes available. Therefore, the 75-ampere detection level will identify and de-energize arcing short circuits that are known fire causes.
During the tests, actual current flowing is somewhat less than 75 amperes. The test circuit has 75 amperes available before the arc is introduced. The arc current will be lower because of the impedance of the arc itself. The AFCI must detect the arc current.
Questions have arisen about the ability of the branch/feeder to detect series arcs. The UL 1699 Standard requires that the branch/feeder detect arcs in circuits that deliver 75 amperes and higher fault current. It does not distinguish between series and parallel. These are short-circuit conditions—and are the conditions that drove the industry to develop arc detection. We know that fires occur from these higher energy arcs. This means that true series arcs with no arcing to a grounding conductor, which are at load current values well below 75 amperes, are not detected.
Outlet Circuit AFCI Performance
In considering a device located at the receptacle, it was clear as the standard was being written that the primary function of such a device would be protection of extension and appliance wiring. Detection of series arcs at the lower current level of a single appliance would be important. The device was envisioned to be electrically closer to the appliance and not necessarily in the circuit with the variety of products and conditions on a general branch circuit. Therefore, for the envisioned outlet circuit (OC) AFCI, a 5-ampere detection level was required in the standard for line-to-neutral, line-to-ground and series arcs.
There is a place for each of these devices. As we look at the need addressed by NEC 210.12(A), a branch/feeder AFCI is necessary to protect the entire circuit. Protection would be enhanced if an outlet circuit AFCI were added for extension and appliance wiring.
The ideal device is the combination AFCI located at the source of the branch. The combination AFCI combines the performance of the branch/feeder with that of the outlet circuit in a single unit. With the technology available, why not require combination performance to provide the best available protection for the entire branch?
Causes of Tripping of the Branch/Circuit AFCI
The circuit-breaker branch/feeder AFCI incorporates functions of both an overcurrent protective device and an arc-detection device. It is designed to trip under the following conditions.
Overcurrent.For any current above its current rating it will trip according to its circuit breaker time-current characteristic.
Hazardous arcing.For arcing at current levels of about 75 amperes and above, the AFCI will trip. Commercially available AFCIs will actually operate at some level below 75 amperes. The AFCI will operate faster than a fuse or circuit breaker under short-circuit overcurrent conditions up to about 125 amperes.
Arcing ground faults.The standard requires tripping on faults of 5 amperes and greater. Commercial units will actually detect ground faults of 50 milliamperes and greater. Tripping will be instantaneous, with no intentional delay.
Neutral grounding.If the neutral conductor (grounded-circuit conductor) of an AFCI protected circuit touches grounded metal, the AFCI will trip if the impedance to ground is very low impedance.
Abnormal environments.Some abnormal events may also cause tripping, such as high voltage surges from lightning or utility line surges, voltage or frequency fluctuations from poorly regulated backup generators, or mechanical shock.
More To Come
Part II of this article addresses such questions as which circuits must be protected under the NEC and how to check and troubleshoot installed AFCIs. Look for these questions in the next edition of this magazine.
1. "AFCI Inquiry and Report” by the Consumer Product Safety Task Force of the National Association of State Fire Marshals, August 1, 2002.
Read more by Alan Manche