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Relevance

Posted By David Clements, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Due to new technology, social networking and competition, individuals have many options as to where and from whom they can obtain information. Consequently, associations, the traditional suppliers of industry information, are facing intense pressures. Gone are the days when members would automatically renew their memberships. IAEI is no different and we face many of the same challenges.

In order to grow our membership, we need the assistance of all members; this includes our chapters, divisions and individuals. I’ve announced a new membership drive campaign in which, for new members only, we are offering 18 months of membership for the same price as a 12-month membership (that’s six months of free membership). This is a limited time offer that expires on December 31. You can make a difference by sharing this offer with your friends in the industry who have not yet discovered IAEI.*

I recently read the book, Race for Relevance, 5 Radical Changes for Associations by Harrison Coerver and Mary Byers, which outlines what an association needs to do in order to stay relevant. Interestingly enough, we are running the race for relevance in the right direction. We will never cross the finish line as it will continue to move in a forward direction; however, we can do things to ensure we stay current and remain competitive in today’s market.

So let me touch briefly on things we have been doing to remain relevant.

• We are fulfilling our obligation to our mem-bers, to the electrical industry and to the general public to participate in code devel-opment, to provide premier education and to support the inspection process.

• We are developing a five-year strategic plan for the association, which includes strength-ening our business practices, community involvements, and member educationpractices.

• We are forging partnerships with other organizations within the industry. The most recent agreement is with ICC(International Code Council).

• Following our mission statement of promoting advocacy, IAEI has joined the Electrical Code Coalition in taking the position on early adoption of the NEC without amend-ments. This position is under great pressure from certain in-dustry associations, but the Coalition feels that both the industry and the public need a fair picture of the necessity of early adoption without amendments.

• IAEI has created a new Department of Advertising and Marketing and has commissioned the new director to create and implement a robust marketing plan for IAEI publica-tions, membership, training, and meetings.

• IAEI is enlarging its publication formats to include newer and more relevant platforms. We believe that all members will be excited and pleased with this forward move.

• IAEI will be ramping up its use of social media (Facebook, Twitter and LinkedIn) to market and promote the associa-tion. I encourage you to use these tools. I am now tweeting multiple times a week. You’ll find me @DavidEClements.

• IAEI will be optimizing the development of the board’s insight into current technologies, broader target audience, and industry diversifications.

• Members will find easier password access to their IAEI ac-count information on the website which will interact seam-lessly with the IAEI store and IAEI magazine.

Although IAEI faces the same challenges as all associations, we are up the task. We are ready and willing to embrace our industry as it evolves and to make the necessary changes. As we continue to run the race for relevance, we will not forget to provide the services and products that our members deserve.

David Clements is CEO/Executive Director of IAEI

* If you need more information about this offer, visit our website or call Annette Thomas, director of membership and customer service.

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Tags:  Editorial  November-December 2012 

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Selection of conductors – do we have a problem with this?

Posted By Ark Tsisserev, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Apparently, we do. However, there is no reason to generalize this problem. Although there might be problems (or rather challenges) for the code users in understanding of some requirements related to the selection of conductors, I’ll concentrate on two specific issues that have apparently become a source of confusion:

1. Introduction of Rule 4-006 into the CE Code; and

2. Recent UL/ULC Public Notice release 12PN-51.

So, let’s concentrate on each of these subjects separately.

Our first issue is introduction of Rule 4-006 into the CE Code. Why now?

In order to clearly follow the sequence of events, we need to "unearth” a few relevant bits of history. A number of years ago, the NEC/CEC Ampacity Task Force had been established.

This Task Force was charged with the responsibility to conduct a thorough review of the ampacity values of the NEC Tables 310.16 and 310.17 and the CEC Tables 1–4, and to harmonize these values in both Codes. The reason for such assignment was based on a need to re-calculate the ampacities used in both Codes in accordance with the objective scientific formula and to facilitate necessary changes to both Codes that would prevent excess of the maximum allowable operating temperature at any connected termination. There are many pieces of electrical equipment (fused switches, circuit breakers, panelboards, etc.) that have been tested, marked (and certified to the harmonized bi-national: UL/CSA) product standards based on the maximum permitted operating temperature at 75⁰C.

This fact has been captured by the NEC for quite some time. Article 110.14(C) of the NEC mandates temperature limitations at such termination and requires use of conductors being sized on the ampacity values in 75⁰C column of Tables 310.16 and 310.17.

Until 2012 edition of the CE Code, there was no similar requirement in the CEC, as the previous values of ampacity tables of the CEC were more conservative than in the NEC, and no temperature imitation at conductors terminations were deemed to be necessary. Therefore, users of the CE Code have been routinely selecting conductor sizes based on 90⁰C column from Tables 1–4 for termination on the equipment that is marked for the temperature restrictions up to 75⁰C.

However, after the assignment—to correlate ampacity values had been completed by the NEC/CEC Ampacity Task Force, all values of the NEC Table 310.15(B)(16) [formerly Table 310.16] and 310.15(B)(17) [formerly Table 310.17], and the CEC Tables 1–4 have been harmonized.

The result of such harmonization is seen in both Codes. The 2011 edition of the NEC and 2012 edition of the CEC have absolutely identical ampacity values in these respective tables. If we now compare the ampacities values between 2009 and 2012 editions of the CEC, we’ll see that in the latest edition of the CE Code these ampacities (particularly in 90⁰C column of Tables 1– 4) have been significantly raised.

It is obvious now that the restrictions mandated by Article 110.14(C) of the NEC have to be reflected in the CEC—to prevent unsafe operating temperatures at the point of termination of the conductors to the equipment that is marked with the temperature limitation.

New Rule 4-006 of the CE Code states this requirement as follows:

"4-006 Temperature limitations

(see Appendix B)

"(1) Where equipment is marked with a maximum conductor termination temperature, the maximum allowable ampacity of the conductor shall be based on the corresponding temperature column from Table 1, 2, 3, or 4.

"(2) Where equipment is not marked with a maximum conductor termination temperature, 90 °C shall be used by default.”

Appendix B Note on this Rule provides additional clarification on this requirement:

"Appendix B Note on Rule 4-006

"The intent of this Rule is to correlate the temperature rating of conductors where the ampacity is selected from Tables 1 to 4 with the lowest temperature rating of electrical equipment or any wire connector (terminal connector, lug, etc.). It is intended by this Rule that the ampacity of conductors be selected from the temperature column in Table 1, 2, 3, or 4 that corresponds to the temperature rating marked on the electrical equipment. As an example, where a conductor is terminated on a breaker with a 75 °C rating, the maximum conductor ampacity would be based on the 75 °C column of the Tables. It should be noted that the temperature rating of a wire connector (terminal connector, lug, etc.) that is connected to the equipment may be higher than that of the equipment itself; it is the equipment rating that determines the conductor size, not the lug.”

So, based on the requirement of Rule 4-006 and on the clarification Note on this Rule, it appears to be clear that the conductor ampacity should be selected from the temperature column that is consistent with the maximum allowable operating temperature of equipment to which that conductor is intended to be terminated.

But, what if a RW90 conductor is readily available and is intended to be used by a contractor? Could we use the ampacity value from the 90⁰C column and apply some de-rating factors of Tables 5A–5C? From the discussions on this issue between the designers, electrical contractors and regulators, it appears that there is some confusion in relation to this particular point.

Nobody would argue that a typical RW90 conductor could not be selected, but the ampacity of this conductor would now have to be selected from 75⁰C column of Tables 1–4 of the CE Code.

So, why can’t we select ampacity for a RW90 conductor from the 90⁰C column of a respective ampacity Table and to apply one of the correction factors of Tables 5A–5C?

Correction factors of Table 5A, 5B, and 5C are intended only for the allowable ampacity values obtained from Table 1, 2, 3, and 4.

It should be noted that for equipment with a conductor termination rating of 75⁰C, Rule 4-006 requires the allowable ampacities to be "based” (i.e., to be obtained) on the 75⁰C column of Table 1, 2, 3, or 4. The Rule does not permit basing the allowable ampacity on any other value than the value obtained from the 75⁰C column for equipment with a required conductor termination rating of 75⁰C.

The rationale for Rule 4-006 was to recognize how the equipment was tested during the certification process.

If we’ll review the CSA standards C22.2 No 4 Enclosed and Dead-Front Switches; C22.2 No 5 Molded-Case Circuit Breakers; Molded-Case Switches and Circuit-Breaker Enclosures; C22.2 No 29 Panelboards and enclosed panelboards and C22.2 No 244 Switchboards, we’ll find that all these standards require the conductor used during the temperature testing to be based on a 75⁰C ampacity.

The maximum allowable operating temperature of any circuit should be always limited to the lowest permissible value of such temperature for any component of the circuit.

In a practical sense, a conductor ampacity is the operating temperature for a conductor that is fully loaded to the applicable values in Tables 1, 2, 3, and 4, and this ampacity would be equal to the temperature rating of the conductor.

For example, if 4X350 kcmil copper conductors rated at 75 degrees C are installed in four raceways at an ambient temperature of 30⁰C and loaded to 1200 A, the operating temperature of these conductors would be 75⁰C. If we would select the 90⁰C rated conductor for the same example, the operating temperature of the conductor would be also 75⁰C.

If, in another example, 3X#3 RW90 conductors in a raceway are loaded to 115 A in accordance with Table 2 of the CEC, then such conductor loading would result in a conductor operating temperature of 90⁰C.

When the number of #3 RW90 conductors is increased (let say to eight conductors), Table 5C would require a correction factor of 0.7. In this case, 115 A x 0.7 = 80.5 A. Therefore, each of these 8X#3 RW90 conductors loaded to 80.5 A will again operate at the temperature of 90⁰C.

To limit the operating temperature of the conductor to 75⁰C (the maximum allowable temperature rating of the equipment) the ampacity would need to be selected from the 75⁰C column, and then the correction factor of Table 5C should be applied to the selected ampacity. In the example of 8x#3 RW90 conductors in the raceway (from the 75⁰C column of Table 2 and from Table 5C) 100 A x 0.7 = 70 Amp. Therefore, each of these 8X#3 RW90 conductors loaded to 70 Amp will again operate at the temperature of 75⁰C.

The main issue here is the effect that the operating temperature of the conductor has on the equipment to which this conductor is connected. The conductor can handle the ampacity, but the equipment was not tested with terminations above 75⁰C.

If, in addition to the discussion above, the selected 3X#3AWG RW90 conductors are terminated at the equipment rated at 75⁰C, and these conductors are operating in the ambient temperature exceeding 30⁰C, then the appropriate de-rating factor of Table 5A should be applied to the ampacity already selected from the 75⁰C column. If, for example, the ambient temperature is 40⁰C, then 100 A ampacity must be multiplied by the correction factor 0.91 from Table 5A, as the actual conductor used in this example is RW90 (and not RW75). Therefore, each of these 3X#3 RW90 conductors would be now loaded to 100 A x 0.91 = 91 A, and these RW90 conductors will again operate at the temperature of 75⁰C.

And, of course, regardless what correction factors are used for the selected ampacities, the resulting (decreased) ampacity of conductor should be checked for compliance with Rule 8-104 to ensure that it is not less than 125% of the calculated load.

Let’s now discuss the second issue – Recent UL/ULC Public Notice release 12PN-51.

UL and ULC have recently published the following notice. (However, from the perspective of application of this notice for the Canadian electrical industry, the discussion is limited only to the ULC portion of this notice).

"UL and ULC announce important changes to certification programs (Release 12PN-51)

"UL has recently conducted research on a wide array of current products and systems originally certified under UL 2196, Tests for Fire Resistive Cables and ULC-S139, Standard Method of Fire Test for Evaluation of Integrity of Electrical Cables and determined that they no longer consistently achieve a two-hour fire-resistive rating when subjected to the standard Fire Endurance Test of UL2196 or

ULC-S139. "Consequently, UL and ULC will not be able to offer certification to the currently existing program related to these standards.

"As a result, manufacturers are no longer authorized to place the UL mark or ULC mark on the following products:

"UL Classified Fire Resistive Cable (FHJR)

"ULC Listed Fire Resistant Cable (FHJRC)

"UL Listed cable with "-CI” suffix (Circuit Integrity)

"Furthermore, UL has removed from its certification directory all Electrical Circuit Protective Systems constructed with Fire Resistive Cable (FHIT).”

This notice has created a significant adverse impact on all electrical safety stakeholders, and particularly on the manufacturers of wiring products and on the electrical designers, and has become a subject of confusion in the electrical industry.

It appears from the early UL generic letter to the manufacturers of wiring products that UL (and in Canada – ULC) has published the attached public notice based on concerns that certain wiring products (which in addition to being designed, constructed, tested and certified to the applicable CSA Part II standards), are designated as "fire resistive cables” after being tested to the ULC standard S139, may, in fact, no longer conform to the ULC S139 circuit integrity test.

Apparently, some of such cables have failed the ULC S139 test, when they are installed in a metal conduit with the interior wall constructed with zinc coating, as at high temperatures a zinc coating may interact with copper conductors creating a brass alloy that melts at a lower temperature than copper conductors, thus impacting on the circuit integrity.

If the specific technical concern identified above is accurate (i.e., if it is limited to the melting of alloy inside the rigid metal conduit), the ULC following statement "manufacturers are no longer authorized to place the ULC mark on the following products: ULC Listed Fire Resistant Cable (FHJRC),” made in the referenced "Public Notice release” appears to be highly questionable, as the compliance with the circuit integrity test method described in the ULC S139 does not apparently require a certification monogram (in addition to the monogram signifying compliance of a cable with the applicable CSA safety product standard).

It is interesting to note that in accordance with Clause 6.1A of ULC S139 – the product shall be marked with the circuit integrity rating only, and not with the additional certification monogram. The ULC Notice indicating "ULC will not be able to offer certification to the currently existing program related to these standards” also appears to be questionable, as Clause 3.2.1 of the ULC S139 states the following: "Cables shall be installed in raceways or supports as permitted for that cable type by the Canadian Electrical Code.”

Based on this provision of Clause 3.2.1 of the ULC S139, each particular test assembly in accordance with this standard must reflect condition of use of a specific type of cable under relevant installation requirements of the CE Code. This means that if an armoured cable is being tested for circuit integrity in accordance with the ULC S139, such cable would not be tested in a raceway, as armoured cable is not intended by Table 19 of the CE Code to be used in raceway. Accordingly, if a typical communication, community antenna or Class 2 circuit cable would be subjected to the test in accordance with ULC S139, such test assembly would not have to include a raceway, as in accordance with the CE Code, communication, community antenna or Class 2 circuit cables are not specifically required to be installed in raceways. These examples clearly indicate that the technical concerns which prompted the ULC to publish the referenced notice would not be warranted for all test methods of the ULC S139, and that suspension of the certification of the circuit integrity tests to absolutely all types of test assemblies which are set up in accordance with Clause 3.2.1 of the ULC S139 to comply with the conductors installation requirements of the CE Code, is not necessarily warranted.

One of the main concerns with this ULC Public Notice relates to the fact that the compliance with the test methods for circuit integrity of conductors in accordance with the ULC standard S139 is mandated by the National Building Code of Canada (NBCC) and by the ULC standard S524 "Installation of fire alarm systems,” and both these documents are legally adopted for a regulatory purpose in the respective Canadian jurisdictions.

From a practical view point, the ULC Public Notice will leave the electrical industry practitioners with no other option, except for resorting to means for fire protection of conductors (required by the NBCC to be protected against exposure to fire) by encasing conduits containing such conductors in at least 100 mm of concrete.

This Public Notice appears to disregard the fact that a typical MI cable designed and constructed to very stringent requirements of the CSA standard C22.2 No.124 (which also incorporates provisions for fire rating) would not be allowed to be used for the purpose of complying with the NBCC 1 h or 2 h fire rating requirements, as Clause 6.7 of this CSA standard states the following

"6.7 Fire rating

"Cables marked in accordance with Clause 5.3 shall comply with the requirements of ULC-S139.”

It should be noted that the ULC is aware of the industry concerns, and hopefully this matter will be resolved, when this article is published.
 
Meanwhile, as usual, the electrical inspection authorities should be consulted on all applicable aspects related to the issues discussed in this article.
 

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Tags:  Canadian Perspective  November-December 2012 

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The Slash-Rated Breaker and Shared Neutral Applications

Posted By Thomas A. Domitrovich, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012
Think back one or maybe more years ago when you had to assemble that latest purchase in front of the Christmas tree; picture the moment, if ever, you decided to open the assembly instructions and read them. It could have been before you got started — as you were drinking your coffee looking at the box and all of the parts. Or perhaps it was half way through when you couldn’t figure out how two parts went together. If you’re anything like me, it was when you were all done and you had a handful of parts left over. When it comes to electrical products, no matter how simple or how many times you’ve installed them, reading the labels on the products and the instructions can go a long way for electrical safety. Familiarity can indeed breed contempt in this arena. Today we’ll focus on slash-rated and non-slash-rated breakers and their applications.
 
This is an important topic as code requirements have driven more use of handle ties. Two 1-pole circuit breakers can be tied together with an approved handle tie but close attention to the markings and listing of the products is important to ensure they are not applied outside of their rating. Observing labels and understanding what they mean is an important first step.
 
Photo 1. 1-pole thermal magnetic circuit breakers rated 120/240V
Photo 1. 1-pole thermal magnetic circuit breakers rated 120/240V

Slash Ratings
The UL white book, in the "Marking and Application Guide – Molded Case Circuit Breakers,” which is available at www.ul.com/whitebook helps us understand the markings of circuit breakers. The General section, Item 3 entitled "Voltage Rating” illustrates that all breakers are required to be marked with their voltage rating. This marking is important to the proper application of these products, to ensure they are not applied at a voltage outside of their rating. All UL 489 Molded Case Circuit Breakers are marked with a voltage rating chosen from the following:

DC Voltage Ratings:
60, 125, 125/250, 160, 250, 500 and 600 volts

AC Voltage Ratings:
120, 127, 120/240, 240, 277, 347, 480Y/277, 480, 600Y/347 and 600 volts
 
Photo 2. Two 1-pole breakers and an approved handle tie before assembly
Photo 2. Two 1-pole breakers and an approved handle tie before assembly


This reference identifies the existence of breakers that can be designated with a single voltage rating or a slant (or slash) voltage rating. A circuit breaker that carries a single voltage rating is intended for use in circuits where the circuit voltage and the voltage to ground do not exceed the voltage rating of the breaker. A slash-rated breaker, such as 120/240 V, is intended to be used in circuits where the circuit voltage does not exceed the higher of the two voltages and the voltage to ground does not exceed the lower of the two voltages. This reference notes the following when it comes to a slash-rated breaker:
 
"Two-pole independent-trip breakers and single-pole breakers with handle ties that are rated 120/240 V ac have been investigated for use in line-to-line single-phase circuits or line-to-line branch circuits connected to 3-phase, 4-wire systems, provided the systems have a grounded neutral and the voltage to ground does not exceed 120 V.”
 
A peek into UL 489 provides an understanding of what extra testing and requirements a slash-rated breaker must endure to qualify for this slash rating. Section 6.1.5 entitled "Operating Mechanism” includes Section 6.1.5.3 stating the following:
 
"6.1.5.3 Single-pole circuit breakers rated at 120/240 V ac or 125/250 V dc shall have provision for the use of handle ties. Handle ties, when installed, shall:
a) Operate both circuit breakers when either circuit breaker handle is manually operated;
b) Not be readily removable; and
c) Not obscure the ampere marking on either circuit breaker.”
 
These important physical requirements/qualities of an approved handle tie illustrate what an approved handle tie means physically for a circuit breaker. Section 7 of this same UL standard covers the performance based testing for breakers with the handle tie in place. Section 7.1.1.12 is specific for single-pole breakers rated 120/240 V. I’ll note here that most single-pole breakers that we encounter on residential systems, as depicted in figure 1, are slash-rated in this manner. This permits the use of approved handle ties in the field in cases where a contractor decides to "share the neutral,” a practice some electrical contractors employ to reduce the amount of wire required for home run circuits. Section 7.1.1.12 identifies the testing that must be performed on these single-pole slash-rated breakers as follows:
"7.1.1.12 If a single-pole circuit breaker is rated at 120/240 V ac or 125/250 V dc, see 6.1.5.3, two such circuit breakers shall be tested together in the intended manner as a 2-pole independent-trip circuit breaker in the overload, endurance, interrupting, and dielectric voltage-withstand test described below. Two such ‘pairs’ of circuit breakers constitute a set.”

When two 1-pole breakers are combined via an approved handle tie, they must both be slash-rated breakers. This ensures that proper testing has been performed on the "pair” of breakers for their application. Even if applied on only single-phase circuits, as is the case of shared neutral applications, this "pair” of breakers may be called upon to interrupt a line-to-line fault, a condition for which they have not been tested if they are rated 120 V only. The above introduces the term independent-trip which operates such that any single breaker in the pair of combined breakers may trip without causing the trip of the other breaker(s). This can be the result of applying an approved handle tie to two 1-pole breakers. Handle ties have become more popular these days due to recent National Electrical Code (NEC) changes.
 
Photo 3. Applying the handle tie to two 1-pole breakers. Note that the ampere rating on the handle will be visible after the application of the handle tie.
Photo 3. Applying the handle tie to two 1-pole breakers. Note that the ampere rating on the handle will be visible after the application of the handle tie.

Shared Neutral Applications
The shared neutral application is familiar to many electrical contractors as sharing the neutral on the home run circuit from the breaker to first outlet can be one way of reducing material costs. Those applications where you would have pulled two 2-conductor (+ ground) wires instead are pulled with a single 3-conductor (+ ground) wire. Section 210.4 of the NEC addresses multiwire branch circuits noting that these circuits are those where all conductors originate from the same panelboard or similar distribution equipment.

An approved handle tie applied to two single-pole breakers for such applications as shared neutral installations ensures the installation meets the requirement of section 210.4(B), "Disconnecting Means,” of NEC 2011 which states:
 
"(B) Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.”
 
Section 210.4(B) does not require the breaker to disconnect all ungrounded conductors in the case of a trip. A breaker that operates such that only that pole which experienced the overcurrent trips while the other doesn’t is termed as an independent trip type of device. This section, rather, requires that when you turn the breaker to the off position all poles are turned to the off position. It is important to note that the construction of the breaker and the position to which the handle moves in the tripped state plays an important role on whether or not the breakers are independent trip. Some breakers trip to center. Applying an approved handle tie to two of these breakers may result in independent trip functionality as without an internal link between the two breakers, a single handle itself tripping to center may not pull the handle of the second breaker to the off position. The functionality of tripping both or all poles due to one single-pole seeing a fault, if present, is a common trip type of two pole device. Due to the internal linkages on these devices they are manufactured to ship as a two pole device. The manufacturer’s literature will indicate how the device operates, independent or common trip.

Applying the Approved Handle Tie
Care must be taken when applying an approved handle tie to two single-pole breakers in the field. As stated earlier, the practice of doing this was made easy due to the fact that most single-pole breakers you work with in residential systems are slash-rated. Sometimes the fact that most are slash-rated can lead toward a violation due to not reading the labels and checking. I guess this is a good example of the age old phrase "familiarity breeds contempt.” Before you apply an approved handle tie, you must verify that the breaker carries the slash-rating for the application and ensure that the handle tie is approved for use on that breaker. The manufacturer’s literature can be helpful and the label check is even easier. Looking for the slash-rating is a great first step for success.
 
There are single-pole breakers on the market that are not slash-rated. The ground-fault circuit interrupter (GFCI) and arc-fault circuit interrupter (AFCI) breakers are two examples. GFCI breakers provide a technical reason why the use of single-pole breakers in a shared neutral application, with an approved handle tie, is problematic. This is due to the fact that the breakers need all of the current that goes out on the hot to come back on the neutral. These devices act to trip the circuit if the current going out on the black wire (hot) does not equal the current that comes back on the white wire (neutral). Sharing the neutral with two GFCI breakers with this construction will result in instant tripping the moment a load on either breaker is energized.
 
Single-pole AFCI breakers on the market today, to the author’s knowledge, also carry a single voltage rating of 120 volts. Applying two 120V rated (NOT 120/240V) single-pole AFCI devices with an approved handle tie to serve shared neutral loads would be applying these devices outside of their rating. The bottom line for applying an approved handle tie to any pair of 1-pole breakers is to check the label for the slash rating. Slash-rated breakers are available, even for GFCI and AFCI circuits.
 
Photo 4. Final assembled 2-pole breaker with handle tie applied and approved
Photo 4. Final assembled 2-pole breaker with handle tie applied and approved

National Electrical Code Requirements
The NEC is not silent when it comes to handle ties and their application as discussed above. The various sections in the NEC that address this topic can stand for a little improvement but the requirements that align with the UL standards are there. Let’s explore this topic with respect to the NEC and I trust you’ll see what I mean.
The key sections in NEC 2011that are important for this discussion include the following:

Article 210 Branch Circuits
210.4 Multiwire Branch Circuits
210.4(B) Disconnecting Means

Article 240 Overcurrent Protection
240.15 Ungrounded Conductors
240.15(B)(1) Multiwire branch circuits
240.85 Application

Our first stop is going to be in Section 240.85, Application. This section is within Part VII of Article 240 which focuses on circuit breaker overcurrent protection. The language in this section mirrors that which is in the Marking and Application Guide for Molded Case Circuit Breakers found in the 2012 version of the UL White Book which was previously referenced in this article. Section 240.85 states the following:
 
"A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker’s voltage rating. A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1φ–3φ to indicate such suitability.
 
"A circuit breaker with a slash rating, such as 120/240V or 480Y/277V, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed the lower of the two values of the circuit breaker’s voltage rating and the nominal voltage between any two conductors does not exceed the higher value of the circuit breaker’s voltage rating.”
 
This section provides guidance to help with the proper application of the product within its rating. It offers a simple check to ensure that you don’t exceed the rating of the device — measure the voltage between any two conductors. Let’s use a shared neutral application for this discussion (figure 1). Figure 1 illustrates the terminations in a shared neutral application where two 1-pole breakers have had an approved handle tie applied in the field. Measuring the voltage between any two conductors yields a maximum voltage potential reading of 240V between H1 & H2. If both or any single 1-pole breakers were rated only 120V, a violation of section 240.85 would result.
 
Section 240.15(B) is another area of the NEC that provides guidance for the application of handle ties. 240.15(B)(1) language is not specific on the voltage rating requirements of the two 1-pole breakers being handle tied. This section simply permits an approved handle tie to be applied in the field. 240.15(B)(2) does specify the voltage rating of the breakers handle tied for line-to-line connected loads. It is possible for one to mistakenly assume that two 1-pole breakers rated 120V may be handle tied as long as they are supplying single-phase line-to-neutral loads based on the words in these two sections. This would be in error, though, as other sections of the Code and UL requirements mentioned above help us to understand the proper application of these devices.
 
Section 240.15 has seen considerable changes over the years. Previous editions of the NEC, going at least back to the 1987 version of the Code, saw this "Ungrounded Conductors” section as 240-20. 240-20(B) in NEC 1987 read as follows:
 
"(B) Circuit Breaker as Overcurrent Device. Circuit breakers shall open all ungrounded conductors of the circuit.”

This had one exception:
 
"Exception: Individual single-pole circuit breakers shall be acceptable as the protection for each ungrounded conductor of 3-wire direct-current or single-phase circuits, or for each ungrounded conductor of lighting or appliance branch circuits connected to 4-wire, 3-phase systems or 5-wire, 2-phase systems, provided such lighting or appliance circuits are supplied from a system having a grounded neutral and no conductor in such circuits operates at a voltage greater than permitted in Section 210-6.”
 
This verbiage was in place, for the most part, at least as far back as NEC 1962. This section saw considerable changes in NEC 1993, NEC 1996, NEC 2005 and NEC 2011. It was in NEC 2008 that the section went from 240.20 to 240.15.
 
NEC 1990 introduced section 240.83(e), Voltage Marking. This section stated the following: "Circuit breakers shall be marked with a voltage rating no less than the nominal system voltage that is indicative of their capability to interrupt fault currents between phases or phase to ground.” This section also included a Fine Print Note (FPN) as follows:
"A circuit breaker with a straight voltage marking, e.g., 480V, may be applied in neutral grounded systems or grounded wye or grounded and ungrounded delta systems. Circuit breakers with slash voltage markings, e.g., 480Y/277V, 120/240, may be applied only in grounded neutral systems.”
 
This section ultimately ended up being split between 240.83(e) and a new 240.85, Application, section which was added in NEC 1996. This section has seen some changes since to better clarify the proper application of a circuit breaker.
 
This review illustrates an important aspect of the NEC — in some cases, many different sections of the Code work together to ensure a safe installation. When you think you have found the answer to your question quite easily, look a little harder; you just may learn something more.
 
Figure 1. Shared neutral termination on two 1-pole breakers with handle tie. The voltage between any two conductors cannot exceed the rating of the breaker (240.85).
Figure 1. Shared neutral termination on two 1-pole breakers with handle tie. The voltage between any two conductors cannot exceed the rating of the breaker (240.85).

Summary for Safety
We’ve talked a lot so far about ratings, UL requirements for single-pole and two-pole devices and the NEC. Let’s provide a quick overview via the following bulleted items:
 
  • A circuit breaker that carries a single voltage (120V) rating is intended for use in circuits where the circuit voltage and the voltage to ground do not exceed the voltage rating of the breaker. You cannot apply an approved handle tie to these breakers.
  • A slash-rated breaker, such as 120/240, is intended to be used in circuits where the circuit voltage does not exceed the higher of the two voltages and the voltage to ground does not exceed the lower of the two voltages. Single-pole breakers with slash ratings can have approved handle ties applied for shared neutral applications.
  • GFCI single-pole devices only rated 120V cannot have an approved handle tie applied. This not only is a UL violation but also results in instant tripping of the device. For those shared neutral applications, 2-pole 120/240V rated GFCI breakers are available.
  • AFCI single-pole devices rated 120V cannot have an approved handle tie applied. This is a violation of the UL listing and for those shared neutral applications 2-pole 120/240V rated AFCI breakers are available. Should a 1-pole AFCI carry a 120/240V rating, an approved handle tie may be applied for shared neutral situations.
 
The bottom line in the application of an approved handle tie is to read the labels and the manufacturer’s instructions to ensure you are not applying the product outside of its rating.
 
As always, keep safety at the top of your list and ensure you and those around you live to see another day.

Read more by Thomas A. Domitrovich

Tags:  November-December 2012  Safety in Our States 

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UL Certifies First Stand-Alone Replacement LED Tube

Posted By Underwriters Laboratories, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Question 

Does UL List (certify) stand-alone LED (light emitting diode) tubes for direct replacement of fluorescent tubes in fluorescent luminaires? 

Answer

Yes, recently UL has certified (Listed) the first stand-alone LED tube for direct replacement of a fluorescent tube in a fluorescent luminaire. The replacement tubes operate in the existing ballast circuit present in the fluorescent luminaire. They have been evaluated to operate in the ballast circuit so that the LED tube does not adversely affect the ballast operation in the luminaire. These LED tubes are certified (Listed) under the product category Lamps, Self-ballasted, Light-emitting-diode Type (OOLV), located on page 279 of the 2012 UL White Book and will bear a UL Listing Mark and also identify  the type of fluorescent tube it is intended to replace, e.g. 40W/48T12/RS.

These certified (Listed) replacement LED tubes differ from what UL has certified up until this point in that LED tube retrofits and conversions involved modifying an already Listed luminaire by replacing the ballast with a driver or removing the ballast and direct wiring the branch circuit to the lamp holders in the luminaire. These types of LED retrofit and conversion kits are certified under either of the product categories Light-emitting-diode Retrofit Luminaire Conversion Kits (IFAR) or Light-emitting-diode Retrofit Luminaire Conversion Kits for Commercial Refrigerators and Freezers (IFAS) located on page 180 in the 2012 UL White Book or Luminaire Conversions, Retrofit (IEUQ), located on page 173 in the 2012 UL White Book. For these categories, one of the major subassemblies will bear the UL Classification Mark and verbiage identifying that it is a Classified kit for use in specific luminaires.

You can also view the UL Guide Information and certifications online at www.ul.com/database and enter any of the category codes OOLV, IFAR, IFAS or IEUQ at the category code search field.


Question

AFCI Troubleshooting, Online Training at UL Knowledge Services

Answer

UL Knowledge Services (formerly UL University) is offering a free 2-hour online training class that was developed by NEMA (National Electrical Manufacturers Association) and the arc-fault circuit interrupter (AFCI) manufacturers themselves.

This FREE two-hour course will help electrical system installers complete the trouble-free installation of arc-fault circuit-interrupter (AFCI) circuit breakers. It also describes what they should do in the unlikely event that unwanted tripping should occur. Proper installation will result in fewer electrical fires started as a result of low level arcing, contributing to greater safety for those who live in the homes that have AFCI circuit breakers installed in them. It will also reduce call-backs, resulting in more satisfied homeowners.

This course is intended for anyone who installs electrical systems in residences, whether they are single, multifamily or apartment buildings—in other words, anywhere the use of AFCI circuit breakers are required by the National Electrical Code.

Some of the topics covered are:

  • Product knowledge 
  • Code requirements 
  • Wire routing and installation 
  • How to install an AFCI circuit breaker 
  • How to install wiring devices and hard wired equipment 
  • Perform a final system test 
  • How to troubleshoot 
  • Installing AFCIs in existing homes 
  • Success stories and additional resources 

Go to www.ulknowledgeservices.com, select United States as your location and search for "AFCI Basics” register and take the free course.

Tags:  November-December 2012  UL Question Corner 

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Are Type AC and Type MC cables considered pre-wired raceways?

Posted By Joseph Wages, Jr., Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Question

Is the definition of a raceway applicable to Type AC cable and Type MC cable since these wiring methods are factory assembled with insulated conductors? Are Type AC cables and Type MC cables considered pre-wired raceways? KJ

Answer

This is an interesting question, and I appreciate an opportunity to address it. Let’s begin by looking at a few definitions. I am referencing the 2011 NEC for this information. A raceway is defined in Article 100 as an "enclosed channel of metal or nonmetallic material designed expressly for holding wires, cables, or busbars, with additional functions as permitted in the Code. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways and busways.”

In Article 320, Type AC cable is defined as "a fabricated assembly of insulated conductors in a flexible interlocked metallic armor.” Looking closer at 320.100, it further states that "Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.”

Article 330 defines Type MC (metal clad) cable as "a factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking metal tape, or a smooth or corrugated metallic sheath.”

Article 300 will give us further guidance concerning a raceway as 300.18 tells us that "raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors.” This section further goes on to state that "prewired raceway assemblies shall be permitted only where specifically permitted in this Code for the applicable wiring method.”

I could not locate a definition for prewired raceway assemblies and feel that it does not apply to AC or MC cable. Article 354 covers Nonmetallic Underground Conduit with Conductors. This is known as Type NUCC. The definition states that this is "a factory assembly of conductors or cables inside a nonmetallic, smooth wall conduit with a circular cross section.” This item may fall under the nonexistent definition of a prewired factory assembly.

In conclusion, a raceway must be installed as a complete system before the routing or installation of conductors, which also provides for the removal of conductors. Cables are prewired assemblies whereby conductors cannot be installed or removed. Type AC cables and MC cables are not considered pre-wired raceways. They are fabricated assemblies of insulated conductors in a flexible metallic enclosure, interlocking metal tape, or a smooth or corrugated metallic sheath. —Joseph Wages, Jr. IAEI Alternate Rep CMP-3

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Tags:  Focus on the Code  November-December 2012 

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Are there any practical guidelines available to installers and the enforement community with regards to continuous loads?

Posted By Keith Lofland, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Question

A continuous load is defined as "a load where the maximum current is expected to continue for 3 hours or more.” Are there any practical guidelines available to installers and the enforcement community to apply this definition?

Answer

As stated in the question, NEC Article 100 defines a continuous load as "a load where the maximum current is expected to continue for 3 hours or more.” In some cases, the NEC tells us when certain loads are continuous. For example, 422.13 demands that a water heater with "a capacity of 450 L (120 gal) or less be considered continuous loads for purposes of sizing branch circuits.” Most commercial lighting and electric signs [600.5(B)] are considered continuous loads. Unfortunately, the Code does not always spell out clearly when to consider a load as a continuous load for calculation purposes.

This is an AHJ call. Generally, dwelling loads are not considered to be continuous. For example, a table lamp may be left on for 3-hours or more, but that is a very small percentage of the ampacity of the circuit so we would not consider the circuit to be continuously loaded. On the other hand, parking lot lights or public hallway lighting would be a continuous load because the entire circuit would be loaded for 3-hours or more.

The definition of continuous load first appeared in the 1965 NEC. The original proposal called for a continuous load to be "four hours or more.” Subsequent action by CMP-6 on the wire tables in Article 310 settled the time element to three hours or more. This code detective could not find anything in the 1965 NEC substantiation that concluded anything "magical” about the 3-hour time frame, but this was the time frame that was eventually settled upon to define a continuous load. —Keith Lofland, IAEI Director of Education

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Tags:  Focus on the Code  November-December 2012 

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Canadian Electrical Code Appendix B

Posted By Leslie Stoch, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Many of the Canadian Electrical Code rules display a note, "See Appendix B.” Appendix B provides important information on interpreting and applying the rules. To be sure you’re on the right track it’s always a good idea to find out what Appendix B has to say. This article reviews a sample of excerpts from this valuable information source.

Rule 10-700 defines an in-situ grounding electrode as a part of the existing infrastructure, buried a minimum 600 mm below grade and having a surface area equivalent to a manufactured grounding electrode (two rod electrodes or a plate electrode).

Appendix B provides a list of acceptable in-situ grounding electrodes such as three metres of metal water piping, concrete reinforcing rods and iron pilings. It also provides a cautionary note – metal treated with a non-conducting corrosion protection does not satisfy the requirements for an in-situ grounding electrode.

Rule 12-120(4) now requires that the internal conductors of long vertical runs of armoured or sheathed cable must be supported at intervals not exceeding the distances specified in Table 21. Alternative methods of support include a 90-degree bend or several bends totaling 90 degrees at intervals not exceeding the Table 21 intervals, a horizontal run not shorter than the vertical run or a cable designed for vertical runs.

Appendix B explains that a horizontal run that equals or exceeds the vertical length or incorporates a 90-degree bend or several bends equal to 90 degrees reduces the strain on the conductor terminations.

Rule 12-902 permits pulling armoured cables into raceways with a number of conditions.

Appendix B warns that armoured cables may be damaged when pulled into conduit or tubing. Calculations and specifications are required to determine maximum cable lengths. Cable manufacturers should also be consulted for minimum bending radii.

Rules 12-1104, 1154 and 1508 refer to temperature limitations for PVC conduit, duct and tubing and specify that PVC must not be subjected to temperatures in excess of 75°C. However, 90°C rated conductors may be installed at their assigned ampacity ratings.

Appendix B explains that continuously loaded 90°C conductors under conditions of 50% fill and 30°C ambient do not result in temperatures above 75°C. Conductors with insulation temperature ratings above 90°C are also acceptable as long as their ampacities are derated to 90°C.

Rule 12-714 requires that mineral insulated box connectors must be used for mineral insulated cables.

Appendix B explains that mineral insulated cables may have copper, aluminum or stainless steel sheaths. Therefore box connectors must be suitable for use with each sheath material.

Rule 12-012 requires that allowance must be made for expansion and contraction of PVC conduit due to changes in temperature by using approved expansion joints.

Appendix B identifies the PVC coefficient of expansion as .0520 and provides a sample calculation. For a 20-metre run of rigid PVC conduit where temperatures range from minus 40 C to plus 30 C, the change in conduit length is 20 x (40 + 30) x .0520 = 73 mm.

Rule 14-510 specifies that manually operated general-use switches must be approved and marked for each purpose.

Appendix B the required switch markings as follows:

"T” – A switch for control of tungsten AC or DC filament lamps up to 125 volts
"L” – An AC/DC switch for control of AC lamps up to 125 volts
"AC, frequency or phase markings” – A general-use switch for use only on AC circuits

Rules 18-108 and 18-154 specify that cable seals must be provided where cables enter an explosion-proof or flame-proof enclosure or where first terminating in a Zone 1 explosive gas atmosphere.

Appendix B explains that cables are not tested for their ability to withstand an internal explosion and therefore must be sealed. Seals are also necessary to prevent passage through the cables of gases, vapours or flames.

I hope I have convinced you that Appendix B holds a wealth of invaluable information. Spending a few moments to find out what it has to say can provide big dividends.

As with earlier articles, you should always consult with the electrical inspection authority in each province or territory for a more precise interpretation of any of the above.

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Tags:  Canadian Code  November-December 2012 

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Grain Elevator Safety

Posted By Thomas A. Domitrovich, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

What’s tall, holds some dusty stuff, and at times can go boom? You guessed it, grain elevators. This just may be a topic you don’t hear discussed very often, yet there are statistics associated with these structures that may surprise you. Headlines such as "Three More Victims Found after Explosion at Kansas Grain Facility . . .” or "2 Hurt in Grain Elevator Explosion in Tracy, Minn. . .” are very concerning and found all too often. A simple Google search for "grain elevator explosion” brings to light the urgency of safety in these types of facilities. Grain elevators have been around for quite some time and will be around for years to come as they are critical not only to many farmers across this country but also to this country’s economy. The statistics and news reports tell us we need to be concerned about grain elevator safety, which deserves your attention and your efforts when it comes to preventing what is happening across the United States — explosions that claim millions of dollars in property and many lives.

Photo 1. Grain elevators enable the handling of loose grain in large volumes.

Photo 1. Grain elevators enable the handling of loose grain in large volumes.

Background

Grain elevators have been around for a very long time; they were invented in Buffalo in the 1842 /1843 time frame to eliminate the need to bag and handle grain. They enabled the handling of loose grain in large volumes. A grain elevator includes a complex of facilities focused on handling grain. That would include offices, weigh-bridges, storage facilities and more. The United States Department of Labor’s Occupational Safety & Health Administration (OSHA) describes grain handling facilities as those "that may receive, handle, store, process and ship bulk raw agricultural commodities such as (but not limited to) corn, wheat, oats, barley, sunflower seeds, and soybeans. Grain handling facilities include grain elevators, feed mills, flour mills, rice mills, dust pelletizing plants, dry corn mills, facilities with soybean flaking operations, and facilities with dry grinding operations of soycake” (http://www.osha.gov/SLTC/grainhandling/index.html). When it comes to safety concerns, any business that has a grain elevator on-site that is utilized for the storage, transport and/or processing of a raw agricultural commodity is a prime target. As an example, these may also include breweries where malt and other ingredients are stored.

These facilities usually employ a bucket elevator or a pneumatic conveyor to take grain from a lower level to a higher level ultimately deposited in a silo or other similar storage facility. They come in all shapes and sizes from smaller grain elevators found on a farm to large grain elevators run by companies that focus only on this aspect of the grain trade. These larger grain elevator complexes are the beginning of a journey for the grain they hold, which finds its way to grain wholesalers, exporters and local users, being emptied out of the silos or bins by gravity into railroad cars, barges or other movers like trucks. This is a very efficient way to handle massive amounts of grain and beats the backbreaking job of handling bags or sacks of the stuff. It’s a process that is critical to our U.S. economy.

The statistics around grain elevators and dust explosions, in general, command our attention. Over the ten-year period reported in table 1 coming out of a Kansas State University study, there were 16 deaths, 126 injuries and $162.8 million in damage due to "dust” explosions. Grain elevator explosions are specifically called out in this report showing 51 explosions over this ten-year period from 1996 through 2005. More recent statistics are available from OSHA and show that over a more recent ten-year period, 2001 through 2011, there have been 83 explosions 59 injuries and 13 deaths.

Table 1. U. S. Agricultural Dust Explosion Statistics

Table 1. U. S. Agricultural Dust Explosion Statistics

The above statistics cover explosions, but the hazards in these grain handling facilities are many. Having grown up in a steel mill town [Aliquippa] in the Pittsburgh, Pennsylvania, area, I can remember sitting around the table listening to my father talk about the dangers that he witnessed in the steel mill and the lives that were lost. Mills, grain elevators and similar types of facilities have certain things in common; there are high areas, gratings, many rotating machines and ultimately many locations where life and limb are at risk. Workers can be exposed to a wide variety of life-threatening hazards in these facilities. Some examples include, but are not limited to, fires and explosions from grain dust accumulation, suffocation from engulfment and entrapment in grain bins, falls from heights, crushing injuries and amputations from grain-handling equipment. Suffocation is the leading cause of death in grain bins. This typically occurs when a worker enters a filled bin and walks/works on the grain without fall protection. A person can be engulfed and trapped when caught in flowing grain. Bridged grain and vertical piles of stored grain can also engulf a worker who enters a bin. Contrary to what you may think, only a few seconds pass before you realize you are entrapped and engulfed by flowing grain, leaving you helpless to free yourself. Suffocation shortly follows as a result of being buried alive in the grain.

Table 2. Grain Elevator Explosions

Table 2. Grain Elevator Explosions

The bottom line is that the handling and transporting of grain creates many hazards in addition to the hazard of the dust created by the process. Unlike the other hazards, the dust problem is one that can become a ticking bomb. Dust is typically very fine and gets just about everywhere. This dust can become an important piece of the recipe for an explosion. The elements of a dust explosion include fuel, oxygen, containment/enclosure and an ignition source. The dust generated at these grain elevator environments is the fuel.

Dust as a Fuel

Any Boy Scout or Girl Scout can tell you how to start a fire — it doesn’t include grabbing the largest available log and holding a match to it. No, quite the opposite; you gather smaller materials (kindling) and ignite those first. In general, the hazard increases as particle sizes decrease. The surface area to mass ratio of the dust particle is a key criterion with combustible dust. The ability of a particular dust to explode is determined by its concentration in air and is influenced by factors such as chemical composition and particle size. In the January/February 2010 issue of IAEI magazine, the inaugural printing of the "Safety in Our States” column included a discussion specifically on how an electrical fire starts. The basic principles discussed there apply here as well. It was shared in that article that "When it comes to ignition, for a solid to burn, it must be volatilized. For ignition to occur, the material first must be capable of propagating self-sustained combustion. The warming, the heat, causes chemical bonds to break and the material to be decomposed into volatile substances which either ignites in the presence of a pilot or it auto ignites.” In that article, I focused on the burning of building materials; here we are talking about materials of much smaller size which increases the overall ignitible surface area. Dust particles, from a size perspective, are smaller than 0.42 mm (420 microns). For comparison sake, granules are in the 0.42 mm to 2 mm size and pellets are larger than 2 mm in diameter. The size of dust is important as there are code requirements that reference dust particle sizes. Article 500 of the NEC, Hazardous (Classified) Locations, Classes I, II, and III, Divisions 1 and 2, during the 2011 code cycle, introduced a definition for combustible dust as "Any finely divided solid material that is 420 microns (.017 in.) or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) and presents a fire or explosion hazard when dispersed and ignited in air.” Proposal 14-9 of the 2011 cycle Report on Proposals (ROP), which is available at www.nfpa.org/70, was accepted to add this definition. This proposal was submitted by the American Chemistry Council (ACC) to retain the reference to dust size which was recently removed from other documents. This same definition made it into Article 506, as well.

Photo 2. The dust generated at these grain elevator environments is the fuel.

Photo 2. The dust generated at these grain elevator environments is the fuel.

Dust clouds present a very nice recipe for ignition as there is plenty of oxygen and surface area for ignition; but in addition to dust clouds, the presence of layered dust is also a significant safety concern. Dust can settle on horizontal and vertical surfaces, and to some extent, it can also settle on ceilings. This settled dust, depending upon the surface on which it has settled, has an opportunity to dry out, resulting in the lowering of its ignition temperature. This layered dust has been identified to be the source of damaging secondary explosions. Secondary explosions, in many cases, have been much more devastating than the initial explosion which may have resulted from ignition of airborne dust. It very well may have been a small explosion whose resulting pressure waves caused the structural vibrations that were enough to dislodge layered dust which, in turn, became fuel for yet another explosion. This secondary explosion will typically be much larger and result in a chain effect of more explosions, dislodging even more dust carrying the explosions well beyond an isolated location to quite possibly the entire facility.

Ignition Sources

I guess it would be accurate to say you can’t have an explosion without an ignition source. Ignition sources can come in different forms including thermal, mechanical or electrical energy. Welding, cutting operations, matches, lighters, cigarettes and even space heaters are all examples of ignition sources that have been identified in fire investigations as the cause of dust explosions. The source, though, doesn’t necessarily have to be some external activity to the process. The equipment itself can lead to ignition through friction, misaligned belts or pulleys, metallic buckets striking leg casings and slippage of belts and more; these are all sources of ignition. The point here is that you don’t need a flame to create a dust explosion. Over one-half of the dust explosions in Germany in 2005 were from non-flame sources. Common sources of ignition include:

  • electrostatic discharge
  • friction
  • arcing from machinery or other equipment
  • hot surfaces, including, e.g., overheated bearings
  • fire

It is, however, often difficult to determine the exact source of ignition post-explosion. Static charges can occur by friction at the surfaces of particles as they move against one another and build up to levels leading to a sudden discharge to earth. The use of electric power has also been identified. Sparks from the normal operation of switches, contacts, rotating machinery, and fuses can generate sufficient energy to ignite dust clouds. I have read of various incidents that involved electricity, including one where a light bulb with a faulty extension cord was being used to illuminate a bucket elevator boot pit and caused an explosion. The heat generated by arcing and sparking or even glowing contacts can generate the energy needed to ignite dust.

Photo 3. Sparks from the normal operation of switches, contacts, rotating machinery, and fuses can generate sufficient energy to ignite dust clouds.

Photo 3. Sparks from the normal operation of switches, contacts, rotating machinery, and fuses can generate sufficient energy to ignite dust clouds.

The recipe for disaster also includes the presence of oxygen and the containment/enclosure. The influence that oxygen has on fire is quite obvious and it is hard to reduce its presence. The amount of oxygen in air is more than adequate to support grain dust explosions. Falling or airborne dust acts to "mix” the dust particles with air. It is very desirable to minimize this mixing activity for obvious reasons. Combining an oxygen rich mixture of dust particles and a contained area with an ignition source provides the explosion with the right recipe for devastating energy.

The Safety Plan and Operating Procedures

I have two words when it comes to your safety plan — "Coin Up!” For those military personnel out there, you probably know what I’m talking about. Your safety plan is a critical part of your business and when challenged with the words "Coin Up” you should be able to produce it.

For those who may not be familiar, a challenge coin is something the military uses to enhance morale and remind Brothers in Arms of their commitment to each other. The origin of the challenge coin dates back to the Second World War where it was first used by the Office of Strategic Services personnel who were deployed in enemy held France. The coins back then were a local coin used to prove your identity. They were your bona fides that you had to produce during a meeting to help verify who you said you were. These coins may have been standard coins for the area, but they were unique in specific aspects such as the type, date, and a few other unique features of the coin. These details would be examined by each party, and they prevented infiltration into the meeting by spies. Today these coins represent each military individual’s commitment to his or her unit. Other organizations have produced these coins to raise awareness and to build bonds for many different reasons. The tradition of a challenge is the most common way to ensure that members are carrying the unit’s coin. The challenge begins when a challenger draws the coin and slaps it on the table or bar. Those being challenged must immediately produce their coins. Anyone failing to do so must buy a round of drinks for the challenger and for everyone else who has his or her challenge coin. However, if those being challenged produce their own coins, the challenger has to buy the round of drinks for the group. There are many different rules around the challenge but suffice it to say, for the purposes of this discussion, "Coin Up” is a challenge to produce your safety plan.

Photo 4. Combining an oxygen rich mixture of dust particles and a contained area with an ignition source provides the explosion with the right recipe for devastating energy.

Photo 4. Combining an oxygen rich mixture of dust particles and a contained area with an ignition source provides the explosion with the right recipe for devastating energy.

The following is by no means everything you need to include in your safety plan and procedures but are some highlights. Most of these were taken from NFPA 654, "Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids.” The referential documents offered as part of this article should be reviewed and understood and should ultimately influence the content of your safety plan and operating procedures.

Emergency Action Plan (EAP): Include your procedures for reporting of emergencies and evacuations. Include critical operations as well. Your employees need to understand how to assist in orderly evacuations. The EAP should be reviewed with all new hires, when their responsibilities change, and when the EAP changes. Include the EAP in your training. Make sure that you identify and follow applicable federal, state and local laws and regulations.

Grain Handling Requirements: You need at least two emergency escape routes from certain locations. Reference OSHA 1910.272(O)(1) and (2) for the requirements of these escape routes.

Safety Training: Make sure your training is job specific and some may say annually; but more frequent sessions are advisable. It’s important to ensure your employees can identify the hazard and understand how to prevent problems. Dust accumulation is a problem in these facilities. Ignition sources should be understood and identifiable. Those who have to access or enter bins must understand engulfment and mechanical hazards. Make sure they know their entry and rescue procedures.

Housekeeping: As discussed above, layered dust presents opportunities for subsequent explosions after the initial event. Your plans must include proper house cleaning which should call for the immediate cleaning when dust layers are noted to be 1/32-inch of thickness or more over a surface area of at least 5% of the floor area of the facility or the room. This thickness may change based on the type of dust as well. Make sure that there are no surfaces that are hard to get to and clean. Dust will continue to collect in these areas without your knowledge. Only use vacuum cleaners that are approved for dust collection.

Electrical Equipment: The use of appropriate electrical equipment for the environment and the proper wiring methods are very important to safety in these locations. Equipment bonding is very important. Some electrical equipment can become warm or hot. Motors, transformers, lights and other types of equipment not only offer surfaces for dust to rest but also act to dry that dust, again providing the perfect recipe for disaster.

Dust Control: In addition to housekeeping, there are ways to minimize the escape of dust from the process equipment. Ventilation systems should be considered as well as dust filters and collection systems. Minimize or eliminate activities that generate dust clouds, especially if ignition sources are present. As noted above, the ability to identify these dust cloud generating processes and ignition sources is critical.

Inspection: Inspect areas routinely. Make sure you have access to all areas and that there are no hidden surfaces that can accumulate dust.

Ignition Source Control: The ability to identify ignition sources should lead you to be able to limit these sources in your facility. Proper machine maintenance can help here as degrading machines may offer opportunities for friction and sparks to be generated. Heated surfaces and other sources of heat or sparks should be addressed.

Vehicles and Tools: The vehicles and tools on the job site should receive critical review. Maintenance of the vehicles, tools and equipment used in these dust areas is important to eliminate ignition sources and dust cloud generation.

Closing Remarks

Grain elevators are target rich environments when it comes to safety concerns. There are many tools available today to help ensure these facilities operate in a safe manner. We need to read, understand and "Coin Up” when it comes to our safety plans. Grain elevator explosions don’t have to occur. I hope this article stimulates the discussions that need to occur in various publications and educational forums to drive a downward trend in the statistics around grain elevator explosions.

Remember, keep safety at the top of your list and ensure you and those around you live to see another day.


Related Codes and Standards

 

Related NFPA Standards:

 

 

NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities

 

 

NFPA 68, Guide for Venting of Deflagrations

 

 

NFPA 69, Standard on Explosion Prevention Systems

 

 

NFPA 70, National Electrical Code®

 

 

NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Noncombustible Particulate Solids

 

 

NFPA 120, Standard for Fire Prevention and Control in Metal/Nonmetal Mining and Metal Mineral Processing Facilities

 

 

NFPA 432, Code for the Storage of Organic Peroxide Formulations

 

 

NFPA 480, Standard for the Storage, Handling, and Processing of Magnesium Solids and Powders

 

 

NFPA 481, Standard for the Production, Processing, Handling, and Storage of Titanium

 

 

NFPA 482, Standard for the Production, Processing, Handling, and Storage of Zirconium

 

 

NFPA 484, Standard for Combustible Metals, Metal Powders, and Metal Dusts

 

 

NFPA 485, Standard for the Storage, Handling, Processing, and Use of Lithium Metal

 

 

NFPA 495, Explosive Materials Code

 

 

NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas

 

 

NFPA 505, Fire Safety Standard for Powered Industrial Trucks Including Type Designations, Areas of Use, Conversions, Maintenance, and Operation

 

 

NFPA 560, Standard for the Storage, Handling, and Use of Ethylene Oxide for Sterilization and Fumigation

 

 

NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids

 

 

NFPA 655, Standard for Prevention of Sulfur Fires and Explosions

 

 

NFPA 664, Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities

 

 

NFPA 1124, Code for the Manufacture, Transportation, Storage, and Retail Sales of Fireworks and Pyrotechnic Articles

 

 

NFPA 1125, Code for the Manufacture of Model Rocket and High Power Rocket Motors

 

 


Related ASTM Standards:

 

 

E789-95 Standard Test Method for Dust Explosions in a 1.2-Litre Closed Cylindrical Vessel

 

 

E1226-00e1 Standard Test Method for Pressure and Rate of Pressure Rise for Combustible Dusts

 

 

E1491-97 Standard Test Method for Minimum Autoignition Temperature of Dust Clouds

 

 

E1515-03a Standard Test Method for Minimum Explosible Concentration of Combustible Dusts

 

 

E2021-01 Standard Test Method for Hot- Surface Ignition Temperature of Dust Layers

 

 


Related OSHA standards found in 29 CFR:

 

 

1910.22 - General Requirements: Housekeeping

 

 

1910.38 - Emergency Action Plans

 

 

1910.94 - Ventilation

 

 

1910.107 - Spray Finishing Using Flammable and Combustible Materials

 

 

1910.146 - Permit-Required Confined Spaces (references combustible dust)

 

 

1910.178 - Powered Industrial Trucks

 

 

1910.269 - Electrical Power Generation, Transmission and Distribution (coal handling)

 

 

1910.272 - Grain Handling Facilities

 

 

1910.307 - Hazardous (classified) Locations (for electrical equipment)

 

 

1910.1200 - Hazard Communication

 


Read more by Thomas A. Domitrovich

Tags:  Featured  November-December 2012 

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Article 230, Services

Posted By Randy Hunter, Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Article 230 is in some ways the genesis of the electrical system, meaning that it is very often the starting point of the electrical installation for a facility. Therefore, this is where I would usually commence my inspection process. As a rule of thumb, if the service is installed in a good workmanlike manner, the rest of the installation would also look good. However, if the service is a mess, you can generally assume that you are in for a long inspection and several items to note on your inspection record. The service is the location where we have some very specific things that have to happen to insure a good reliable system for the rest of the installation. The scope of this article covers the service conductors and equipment for control and protection of services and their installation requirements.

If we do a little review, the first item to remember is the term service point. Generally, it will be very close to the location of the service; and for most residential installations which are fed underground, the service point is at the meter base (see photo 1). From the service point, we start what we call the "service” which may consist of underground or overheard conductors, and then we will actually reach what most refer to as the service, or the main disconnect. If you will look at the first page of Article 230, you will find one of those handy road maps for the NEC. This diagram is a quick reference as to where you will find the requirements for a service installation.

Photo 1. This photo shows the service point, which is at the conductor terminations below the meter.

 

Photo 1. This photo shows the service point, which is at the conductor terminations below the meter.

 

In 230.2 we find the limitation on the number of services for a building or structure; one service is usually all that is required. However, we may have special conditions which would qualify for an additional service. These are commonly at larger locations which will have fire pumps, emergency systems fed from generators, and now with the sudden rise in alternative energy, we may find other types of services (see photo 3). In 230.2(B), Special Occupancies, we have language which allows multiple services for larger facilities. Often on larger apartment complexes, you may find more than one service. This is commonly true if the serving utility supplies a single-phase service which can be limited in capacity. For example, we are limited to only 600 amps for this type of service by the utility in my area. We’ve even had large custom homes which had more than one service due to this limitation. This condition is covered in (C), and again you should be getting used to the fact that one set of rules doesn’t fit every condition, so we add the last sentence to (C) which is "by special permission.” This means that the AHJ can grant permission depending on justification which he sees fit to accept. An example of this would be some of the newer data centers being constructed where reliability is of the upmost importance, requiring redundancy within the system.

Continuing with 230.2 in (D), Different Characteristics, you will find that if you have the need for different voltages you may be allowed to have an additional service. This is common in a manufacturing facility where the office may be supplied for a 120/208-volt, 3-phase service; however, the plant has larger equipment which is more efficiently run on a 277/480-volt, 3-phase system. The last part of 230.2 is the Identification requirement, which states that if a location has more than one service or a combination of sources, then we will have to properly inform people of the other locations of power feeding that location. This is accomplished by the use of a permanent plaque or directory installed at each service notifying one of all the other service, feeders and branch circuits supplying the building or structure. As I mentioned in the last article, this is the same requirement as found in 225.37. This is more than just a convenience for the electrician, it is also for our first responders who in the event of an emergency need to disconnect all power sources to a facility and to do so in a fast, orderly fashion.

Photo 2. Here is an example of a large service with signage to identify the main. As a local amendment, Las Vegas codes require the main to have a yellow sign, which helps the first responders identify the mains service disconnects.

Photo 2. Here is an example of a large service with signage to identify the main. As a local amendment, Las Vegas codes require the main to have a yellow sign, which helps the first responders identify the mains service disconnects.

Briefly I will mention 230.3, which states that service conductors may not pass through the interior of another building. This leads us right into 230.6 which outlines what is considered to be outside of a building. Here you will find that if conductors are beneath a building under 2″ of concrete or buried 18″ down, or if you have a raceway totally encased in 2″ of concrete within a building, these conditions would be considered outside. In the 2011 edition of the NEC, we now have a new addition to this section, which is that a service riser conduit may pass through an eave when installed on the outside of a building. This is one of those areas I had never considered as inside a building for the short distance that the riser may pass through an eave; however, I guess technically it was.

The next two sections mention that no other conductors shall be contained within a raceway or cable with service conductors, with only two exceptions (which I will trust you to review, as these conditions don’t happen often). However, the requirement for raceway seals in 230.8 is one of the most overlooked and missed inspection items I’ve seen, even though it can have catastrophic results if not followed. Simply put, if you have raceways entering from underground you are to seal them, even spare empty conduits. There are several products on the market which are great for this, even duct seal putty or clay will do the job just fine. One of the reasons for this requirement is that if you have some condition which will cause overheating of the underground conductors and they are installed in PVC conduit, the conduit might exceed its allowable temperature and start to degrade and even off-gas. These gases could be and often are very flammable; so if there is any type of an ignition source, like a loose connection or an arc from a breaker actuation, it may cause these gasses to explode. This makes for great photos, however, it is very expensive to repair and the lost time for this type of failure is huge. The simple task of sealing these with an approved method limits this type of condition and could save thousands of dollars.

We will now cover several items which were mentioned briefly in my previous article. I stated in the last edition that there is a huge overlap between Articles 225 and 230 when it comes to clearances, so this will be a bit of review. However, don’t discount the importance of these requirements, as they are all related to safe installations. So open the code book and please review the actual language as I summarize these again. First in 230.9 and 230.10, we find that we need to keep conductors 3 ft. from any openings, which will include windows, doors, porches, balconies, ladders, stairs, fire escapes or similar locations.

Photo 3. Here is an example of multiple services to one building, the normal power on the right and the alternate energy service on the left.

Photo 3. Here is an example of multiple services to one building, the normal power on the right and the alternate energy service on the left.

Overhead service conductors shall not be installed beneath any openings through which materials may be moved — which would include farm or other locations which may load and unload at an elevated portal — nor shall they block any building openings. And again vegetation shall not be used as a supporting means. Which brings to mind a situation, if you have a lodge pole pine tree that has died, is this still considered vegetation or is it now considered a utility pole? Where is the AHJ when you need him?

In Part II of 230 we get into specifics for overhead service conductors. First, these conductors are to be insulated, with one exception: the grounded conductor may not need to be insulated if it is part of a cable assembly. Next, we find the size and rating requirements. Generally, the conductors are to be sized to carry the calculated load as covered in Article 220; however, we do have a minimum size requirement in 230.23(B) which is 8 AWG copper or 6 AWG aluminum conductors. In 230.24 (A) and (B), we get into the specific clearances for overhead conductors which state they shall not be readily accessible, and it then expands further to explain what makes them meet this requirement. First, they shall have an 8-ft clearance over roofs, with five exceptions. Please read and review these on your own.

Next, we get the clearances from final grade. If the service voltage doesn’t exceed 150 volts to ground and the area is only accessible to pedestrians, then we only need a 10-ft clearance. This would commonly be a backyard. Next we cover residential property and driveways, and those commercial areas not subject to truck traffic, where the voltage doesn’t exceed 300 volts to ground. Here we need 12 feet of clearance, unless the voltage exceeds the 300-volt threshold, then the distance moves up to 15 feet.

Now for the last clearance: public streets, roads, and parking areas. Here we must have an 18-ft clearance. This is very important, as I’ve seen services pulled off walls by tall vehicles as a result of overhead conductors not meeting this requirement. This can obviously be a very dangerous condition. Also, please keep in mind that at certain times of the year we may have additional cable sag, which isn’t covered in the code specifically, but should be a design consideration.

One of the most important items to remember when in this area for those doing residential inspections is the additional clearance needed when dealing with swimming pools. This has to be mentioned here and you should take a moment to go to Article 680.8 and make sure you are aware of these distances, so that if you see a pool the little bell goes off in your head that you should double check all those clearance requirements specifically related to pools. Also note that in the 2011 NEC, we have new language to consider in 230.24(E) which mentions the clearance requirements from communication wires and cables.

Articles 230.26 through 230.28 deal with the attachment and support of overhead service conductors. The point of attachment shall never be lower than 10 feet, they shall be attached using fittings identified for the use with service conductors, and if the service mast is used as the support of the final span of the service conductors, it shall be of adequate strength. I mentioned in the last issue what I considered adequate. All this language boils down to this type of an installation, where the conductors are secured by a wedge clamp device that grips the bare grounded conductor which also has the steel core strand for strength, and then the conductors enter the raceway system through a weatherhead fitting.

Next we need to jump briefly to underground service conductors. These are generally utility-owned up to the meter, but you may have different local conditions. Underground service conductors are required to be insulated for the applied voltage, again with a few exceptions, which I will leave for you to review. The size and rating of these conductors don’t vary much from the overhead conditions. Where we have a different situation, in 230.32, Protection Against Damage, please note that the main reference here is to 300.5, where you will find a fair amount of installation requirements, do and don’ts, which we will cover when we reach that portion of the code. And the last item for underground service conductors is 230.33, which deals with splices. In rare cases, we may have to do splices, and this will refer you to the proper code requirements which may fit your application.

Photo 4. As an AHJ we are called out for all kinds of things. Here we had to investigate why a customer still had power even though he had no meter. However, getting past that issue, this photo is a good example of a weatherhead fitting for the proper conductor entrance to the raceway system, including a wedge clamp device which secures the conductors to the riser conduit.

Photo 4. As an AHJ we are called out for all kinds of things. Here we had to investigate why a customer still had power even though he had no meter. However, getting past that issue, this photo is a good example of a weatherhead fitting for the proper conductor entrance to the raceway system, including a wedge clamp device which secures the conductors to the riser conduit.

We now move on to Section IV of Article 230, which is titled Service-Entrance Conductors, so this would appear to cover both the underground and the overhead applications. Section 230.40 states that each service drop, overhead service conductors, underground service conductors or service lateral shall only serve one set of service-entrance conductors. A little review here: remember the difference between overhead and underground service conductors and the overhead drop and the service lateral is dependent on who owns that portion of the system. The ironic part of 230.40 is that we follow it up with nearly half a page of exceptions to this simple one sentence requirement. One of these exceptions will allow multiple service-entrance conductors if we have multiple occupancies. From my experience, when you have a condition which isn’t simply a one-on-one situation, I would recommend reviewing this section of the code carefully to see which condition best matches what you are seeing in the field and work from there.

Moving on, I want to jump up to 230.44. I mention this only to introduce you to the fact that a cable tray installation is permitted for service-entrance conductors.

Let’s move on to more of the mechanics of service installations. In 230.54, we actually begin with the requirements for service heads where the conductors enter a raceway system. Here we cover some simple but very essential items related to how to make sure we have a good weatherproof installation and points of attachment, so we do everything possible to prevent moisture infiltration into our equipment (see photo 4). This would include a drip loop, which is one of the most basic items which I see being done poorly. The intent of a drip loop is to provide a path for water that comes in contact with the wire to drip off of a low point without directing the water into the raceway or into the connections.

So we have danced all around services, but the most basic item in a service we haven’t touched yet, and we finally get to it in Section V, Service Equipment – Disconnecting Means. Now comes the basic items that we typically train combination inspectors to concentrate on when doing service inspections, many of which are service change-outs or upgrades (see photos 5 and 6). The first item is that a means shall be provided to disconnect all conductors in a building or structure from the service-entrance conductors. In 230.70(A) we explore locations for these disconnects. The main rule is that they shall be in a readily accessible location, followed by an item stating that they shall not be in a bathroom. This leads to a little humor as bathrooms are a location I would not consider to be always readily accessible anyway. However, as we’ve said before, much of the code is written due to various interpretations which have caused the need for clarification. The next obvious but frequently missed item is that all service disconnecting means must be suitable for the prevailing conditions; this may require a certain rating of the equipment, or protection.

We continue into 230.71, where we are given the maximum number of disconnects for each set of service-entrance conductors. You will notice that I stated this in a particular way, as I’ve had enforcement issues before where we have tried to state that you are only allowed a maximum of six switches per building for disconnecting means; however, the code doesn’t exactly state that. If you have multiple sets of service-entrance conductors, you can have up to six for each set. Also we have a list of additional items which may be in your service equipment but are not included in this requirement, such as power monitoring equipment, surge-protective devices and a couple of other items.

Grouping of the Disconnects, 230.72, covers the requirement to have disconnects grouped. One of the most important items is that each disconnect shall be marked to indicate the load served: this is a must (see photo 2). The allowance for additional disconnects for such things as fire pumps, emergency systems and such are allowed above the six disconnect rule, but the code wants these separated from the others. The exact words are that these shall be "remote” from the others, so this is an AHJ call as to what is "remote.” One of the other issues that I’ve seen in multi-occupancy businesses is the fact that each occupant shall have access to the service disconnection means. This can be a real issue when the electrical rooms are often locked and the owners don’t like to give every tenant keys to the room. One reason for restricted access is to prevent tenants from storing stuff in the electrical room. Remember, we must maintain proper working clearances, and storage and electrical rooms don’t go together. One of the worst I discovered was a shopping center that decided they needed a security staff. Of course, they had to have an office to work out of, so they made the electrical room into a security office, complete with desks, chairs, microwave, lockers and more.

Electrical rooms that have service disconnects in them have to be maintained and have to allow easy access so that in the event of something getting out of hand, or the need arises to shut down a unit, it can be done without delay or creating a hazardous condition.

Photo 5 and 6. These photos show why we are writing these articles, because as combination inspectors we are running onto these types of code violation installations daily.

Photo 5 and 6. These photos show why we are writing these articles, because as combination inspectors we are running onto these types of code violation installations daily.

This leads to another issue we need to mention here; often these electrical rooms may be very large and the location of the multiple main disconnects may not always be obvious. It could even be on the backside of the equipment you see when you first enter the room. In these cases, we need to provide some form of information as to where each disconnect is. Remember, we could be dealing with first responders who are not familiar with all forms of electrical equipment, so proper signage and whatever else can be done to direct them to each main disconnect will be helpful.

Locally, one option was to paint yellow lines on the floor to guide firefighters to each switch location. We have to keep in mind that personnel may face conditions that are not optimal, such as impaired visibility due to smoke, so the markings on the floor may give us the most advantageous condition. Along with this thought, 230.77 states that it shall be plainly indicated if the switch is in the open (off) or closed (on) position.

Moving along, we have to review the rating of disconnects. Here we find some minimum sizes for certain types of services. First, it must be sized according to the load calculated back in Article 220. Now for some special conditions, if you have a one-circuit installation, then the minimum service shall not be smaller than 15 amps, as detailed in 230.79(A). In (B), a two-circuit service is limited to 30 amps. Moving up to a one-family dwelling in (C), the minimum is 100 amps, 3-wire. And then for the all others, there is a catchall in (D) where the smallest service shall be 60 amps.

Section VII, Service Equipment – Overcurrent Protection, starts with a very basic requirement: each ungrounded conductor shall have overcurrent protection. Further, the rating of this overcurrent device shall not exceed the rating of the conductor ampacity. However, no overcurrent device shall be installed in the grounded conductor, unless the breaker is one that simultaneously disconnects the grounded and the ungrounded conductors. The service overcurrent device shall be an integral part of the service disconnecting means or shall be located immediately adjacent thereto.

The last thing we need to review in this article is 230.95, Ground-Fault Protection of Equipment. There are a few conditions that have to be met to kick in this requirement. First, the service has to be rated 1000 amps or more, and be a solidly grounded wye service of more than 150 volts to ground but not exceeding 600 volts phase-to-phase. So what fits this? It would commonly be our 277/480 wye services. The grounded conductor shall be solidly connected to ground through a grounding electrode conductor. The other information related to this requirement covers the settings, fuses, and the performance testing requirement. Generally speaking, on the ground fault protected systems we had in our area, we required third party testing. This would insure that the devices were set at the proper settings according the installation and the design professional’s requirements. From the factory, the settings are generally set to minimums which will cause nuisance tripping if not adjusted properly. We would then get a copy of this report and submit it as part of the record for the job. This was the best way, due to the time and equipment required, for this type of testing to be conducted. One extra note here, as simple as this may sound it is always a good idea to have this done and the report in hand before you authorize it to be energized.

This concludes Article 230; once again we have only hit the high spots and provided information which is common in the field and for testing purposes. Please take the time to thoroughly review the article in detail for those areas not specifically covered here. In the next issue, we will cover Article 240, Overcurrent Protection.


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Appreciating Hazardous Areas

Posted By Steve Foran, Thursday, November 01, 2012
Updated: Wednesday, December 12, 2012

Photo 1. Electrical wiring in a hazardous (classified) locationIt was the turn of the century and after thirteen years working on the utility side of the transformer I took on the role of managing a Hazardous Area Electrical Training Center. Ironically, at the time I was completely unaware of hazardous areas. Hey, everyone has to learn about something for the first time.

During my first week, I took the most popular course offering. It was an introductory course and I learned about glanding, zones, divisions, IS systems, standards, work methods and many concepts about which most people, including most electrical professionals, know very little.

A half dozen electricians and technicians, all of whom were experienced in working in hazardous areas also attended the course; their presence really enriched the learning. As the course ended and comments were openly shared, I learned a big lesson.

Every single participant commented that although they had heard this was a good course they did not think that there would be much that they would learn — because they already had lots of experience. And without exception every person (including senior engineers who governed electrical inspections) said, "I had no idea there was so much I did not know about hazardous areas.”

Therein lays the universal truth. People tend to strongly believe that their knowledge, beliefs and convictions are complete and correct. This belief in our abilities is often so strong that we do not consider that we might be wrong or that maybe, just maybe, we do not have all of the information.

Truly, there is far more that you do not know than what you know. This is OK. However, it is a problem when you think you are right when you are wrong. And when it comes to hazardous area electrical work, thinking you know what you are doing when you are wrong is a major problem that could lead to a catastrophe.

I am no longer involved with the training center which has since scaled back operations for a number of reasons, the main one being that we could not get enough people to believe that there were things about hazardous areas that they did not know. Companies and individuals most frequently justified that they did not need to take the hazardous area electrical training because they already knew it. Yet participants’ feedback repeatedly mentioned that they gained knowledge and skills that they thought they already had or did not need.

There are two ideas you can use from this.

The first is very simple and specific to hazardous areas. If your work involves hazardous areas, I do not care how much you already know, commit to continually upgrade your knowledge in this field (kudos to IAEI for focusing on this important topic in this issue).

The second is concerned with your talents and applies more generally. It is very important to recognize and appreciate the skills, knowledge and abilities that you do possess. Not that these alone define you as a human being, but they make up a large part of who you are. It is also important to appreciate these aspects in the people around you. That is, if you want them to feel valued.

However, there is a balance that you must find in appreciating your talents and developing your talents (as well as those of others). Knowing your limitations and acknowledging that you do not know everything enables you to use your talents wisely and leads you to develop and improve them. When you do this, you honor and respect your talents. This is a true sign of appreciation — appreciation to yourself and to all those who have contributed to your talents.

The great thing is that when you come to truly appreciate your own talents and abilities you will settle for nothing short of excellence… guaranteed.


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