Posted By Jeff Greef,
Monday, September 16, 2013
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Most residential electrical services are not
designed to accept two sources of power, but they are often utilized for the purpose
of connecting PV systems in addition to utility power. NEC Article 705
provides accommodation for such connections, but sometimes these accommodations
cannot be used without replacing the service enclosure, or adding a distribution
panel, or making a supply-side connection, all of which entail additional cost.
Occasionally installers get "creative” by tapping directly into feeder
conductors coming off the service to a subpanel in the house. Article 705 is
silent on this specific method, and controversy exists as to whether it is a
compliant method at all. Jurisdictions must decide for themselves whether this
is compliant; and if they do allow it, examiners and inspectors must be aware
of how such an installation triggers the provisions of Article 705 which are
meant to prevent the overloading of conductors or busbars. This article
explores the specific issues encountered in such an installation.
For a broader treatment of NEC 705.12(D)
regarding requirements for making load-side connections for PV systems, see the
papers and articles on the subject written by John Wiles of the Institute for
Energy and the Environment at New Mexico State University. Those articles are
referred to at the end of this one. Mr. Wiles has written extensively on the
fundamental intent of 705.12(D). The focus of this article is how 705.12(D) comes
into play only in the case of a load-side tap. This specific issue brings the
fundamental intent of this code section to bear and so requires a brush up on
the basics of these provisions. See John Wiles’ article in the January-February
issue of IAEI magazine, "Unraveling the Mysterious 705.12(D) Load Side
PV Connections,” which demonstrates the basic intent of these provisions as
they pertain to connections at a load center bus bar with a breaker. Mr. Wiles’
article does not address the issue of tapping into feeders; however, the same
principles that come into play at bus bars with breakers also apply with
feeders and taps.
When a PV system is connected to a load center by a
breaker, the problem that can occur is overloading the busbars (see figure 1).
For example, if the main disconnect and
busbars are rated at 200 amps, and the PV system is capable of producing 40
amps, it is then possible to pull 240 amps off the busbars via feeders and
branch circuits, if the users of the system connect enough equipment simultaneously. Section 705.12(D)(2) requires that the "sum
of the ampere ratings of overcurrent devices in circuits supplying power to a
busbar or conductor shall not exceed 120 percent of the rating of the busbar or
conductor.” So, 240 amps are allowed onto busbars rated at 200 amps. But,
705.12(D)(7) requires that PV breakers be located at the opposite end of the
busbar from the utility feed. Figure 1 shows why. If the PV 40-amp breaker is
located adjacent to the utility feed, the sum of amperage on the busbars
immediately after that breaker can be 240 amps, too high for the metal of the
busbar. But, if the breaker is located at the opposite end, this cannot occur,
since power is fed from two different directions. As we will see, a similar scenario can exist
when tapping into feeders with a PV system.
Figure 1. PV load side connection at breaker complaint and non-compliant breaker locations
Tapping into Feeders
Figure 2 shows conductors from a PV inverter
connected to the system by tapping into feeder conductors coming off a breaker
in the service panel. The figure shows a service that has very few breaker
slots, only enough for feeders to a subpanel and several others for loads such
as AC and range. On such a panel, if all slots are taken, the installer cannot
add a breaker to connect the PV. The connection could be made with a breaker at
the subpanel (if all rules are followed), but routing conduit to a subpanel
inside the house is often difficult. A line side connection could be made at
this service panel, but this entails installation of an additional service
disconnect and could violate the terms of listing of the meter enclosure, which
was designed to handle only utility power. A separate subpanel could be
installed adjacent to the service, but this is expensive. Tapping directly into
the feeders is easy, but is it safe and compliant?
Figure 2. Load side PV tap overloaded feeders and busbars
Is This a Tap?
NEC 240.2 defines a tap conductor as "…a
conductor, other than a service conductor, that has overcurrent protection
ahead of its point of supply that exceeds the value permitted for similar
conductors that are protected as described elsewhere in 240.4.” In figure 2,
the overcurrent protection for the feeders exceeds the value permitted for the
PV conductors spliced onto the feeders, but one could argue that those feeders
are not the point of supply for the PV conductors, so that these conductors are
not "taps” at all. However, in the event of fault current between the splice
and inverter, the feeders will supply fault current to the spliced PV
conductors, and the only overcurrent protection to clear this fault is the
feeder OCPD. For this reason the PV conductors qualify as tap conductors, even
though in normal operation they will put current onto the feeders rather than
pull current off of them. If such an installation is allowed by the AHJ, the
tap rules of 240.21(B) must be followed.
Can a Tap Connect PV?
Section 705.12(D)(1) states that the connection
from an inverter must be made "at a
dedicated circuit breaker or fusible disconnecting means.” Figure 2 shows the
tap conductors originating from a 60-amp fused disconnect. Is the connection of
the PV system to the other system made at the tap splice itself, or is it made
at the 60-amp disconnect? Opinions seem to vary on this point. Some consider
that the tap conductors from the splice to the disconnect are part of the other
system, so that the two systems are connected at the disconnect. Others
consider that the tap conductors are part of the PV system, so that the two
systems are connected at the splice. Taking the latter position, the connection
is not compliant because it is not made at a breaker or fusible disconnect, but
rather at a splice. Taking the former, it is compliant since the connection is
at a fused disconnect. Since the code is silent on this issue, each AHJ must
decide this point for himself. The remainder of this article presumes that the
tap connection is judged compliant if it leads to a breaker or fusible
disconnect as in figure 2.
Overloading the Feeders
Figure 2 shows the PV system spliced into the
feeder conductors somewhere along their length. The feeders are protected by a
100-amp breaker. Let us say for sake of discussion that the feeders themselves
and the busbars on the subpanel are rated at 100 amps each, and that the PV
system is capable of putting 30 amps onto the feeders in sunlight. When few or
no loads are being pulled off the subpanel during daylight, the current from
the PV system will backfeed toward the utility. When more than 30 amps are
pulled from the subpanel in daylight, the 30 amps from the PV will go to the
subpanel and the utility will make up the difference. If the building users
connect enough equipment during daylight, they can conceivably pull a total of
130 amps through the subpanel before the 100-amp feeder breaker trips or the
30-amp PV breaker trips.
Let’s say the
users are pulling 130 amps and no breaker trips. The section of the feeders
from the 100-amp feeder breaker to the splice is carrying 100 amps, its maximum
rating. The PV tap conductors from the 30-amp disconnect to the splice are
carrying 30 amps, for which they are rated. But the section of feeders from the
PV splice to the subpanel busbars is carrying 130 amps. As well, the tops of
the busbars themselves, before any breakers take loads off the busbars, are
carrying 130 amps. In this case, both the feeders from the splice and the busbars
are well beyond their ratings and can overheat, distort, burn insulation, etc.,
with no breaker tripping to protect the circuit.
If the PV system were smaller and its breakers were
at 20 amps, the feeders from the splice and the busbar tops would carry 120
amps, which is 120 percent of their rating, and therefore compliant with
705.12(D)(2), the 120 percent rule. However, this installation still violates
the intent, if not exactly the wording, of 705.12(D)(7) which requires that the
connection in a panelboard be made at the opposite end of the busbars from the primary power source. But in this case, we
are dealing with a connection at feeders as well as at a panelboard. Since the
provision regards only a connection at a panelboard, it is debatable whether it
applies to feeders. But still the intent of the provision is clear — the
connections must be made in a way that avoids overloading any given section of
busbar or conductor. In both the 30-amp and 20-amp PV scenarios described
above, such serious overloading is possible because the tap does not connect at
the opposite end from the primary feed. It is added to the primary feed, so
that the sum of amperages enters the feeders mid-way, and the panel from only
one end, in these cases overloading both feeders and busbars.
Size Down the Feeder Breaker
Let us say
that the installer suggests sizing down the breaker for the feeders from 100
amps to 70 amps (in the 30-amp PV scenario). In this case, it will no longer be
possible to pull more than 100 amps through any section of conductor or busbar.
However, this assumes that 30 amps are always available from the PV system
which, of course, they are not when sunlight is not on the PV array panels. At
night the maximum that can be pulled through the subpanel is the 70 amps. If
load calculations for the building show that 70 amps is enough, this is a quick
fix for an otherwise non-compliant situation. If load calculations are over 70
amps, there is a risk of nuisance tripping at the feeder breaker; but the absence
of a working calculation should prevent the installation at all.
Oversized Feeders and Busbars
consider the situation if both the feeders and the subpanel busbars are
oversized to begin with. In figure 3, the feeders are rated for 140 amps and
the subpanel busbars are rated at 200 amps, but the feeder breaker is 100 amps
and the calculated load is below 100 amps. Now the installer taps into the
feeders with 30 amps, and the users connect enough equipment to pull 130 amps
through the subpanel during daylight. Current in the feeders is below their
rating, and the panel is well below its capacity; but this still seems to
violate the provision in 705.12(D)(7) which tells us to locate the PV
connection at the opposite end. Or does it?
The text reads,
"Unless the panelboard is rated not less than the sum of the ampere ratings of
all overcurrent devices supplying it, a connection in a panelboard shall be
positioned at the opposite (load) end from the input feeder location… .” In
this case, the sum of the ampere ratings of the breakers is less than the
ratings of the subpanel busbars or the feeder conductors, so no possibility of
overload exists. This code provision is written to cover scenarios where
busbars are not oversized to begin with, where the addition of another power
source presents a possible overload problem. But the provision allows for
situations where equipment is oversized to begin with, which avoids the
possibility of overload so long as the total amperage fed into the busbars is
below the capacity of the equipment. The same principle applies to the feeder
conductors. Section 705.12(D)(7) is in place to prevent overheated equipment.
It is not necessary to locate the PV connection at the opposite end of the
busbars in this scenario because connecting it ahead or anywhere else cannot
cause an overload.
Figure 3. Load side PV tap oversized feeders and subpanel busbars
Tapped Feeders in a Gutter
shows an installation where three subpanels are fed off of tap conductors in a
gutter. Two possible locations are shown for tapping a PV system onto the main
feeders along with the taps for the subpanels. The same principles apply here
as in the above scenarios. If the PV system tie in occurs upstream of the taps
for the subpanels (PV tap location 1), the section of feeder between the PV tie
in and the first subpanel tap splice can theoretically have an amperage running
through it that is equal to the sum of the main disconnect breaker and the
amperage supplied by the PV system. If this total amperage is greater than 120
percent of the rating of the feeder, 705.12(D)(2) is violated. If it is within
120 percent, it is still necessary to locate the tap at the opposite (load) end
of the feeder, just as you would do with locating a breaker on a busbar, to
comply with 705.12(D)(7). PV tap location 2 shown in the figure is located
where its amperage cannot be added to the amperage coming from the main
disconnect on any given length of the feeder, avoiding overloading that
section. But if the main feeder is oversized to begin with, locating the PV tap
upstream of the subpanel taps is compliant so long as no section of conductor
(or busbar) is overloaded.
Figure 4. Load side PV tap in a gutter with feeder taps
Most residential service load centers are not
designed to accept secondary sources of power such as PV systems. Connecting to
these load centers can be easily done with a backfed circuit breaker, within
certain parameters. But installers are
faced with connecting to a wide range of load center configurations, where
sometimes such a breaker cannot be installed. Sometimes a load-side tap is the
option of choice. Such a connection raises various code issues which inspectors
and installers must be aware of. The basic principles of installation laid down
in the code for use in connecting with circuit breakers also apply when
installing a load-side tap. Thorough understanding of the principles behind the
provisions is essential to ensure safe, effective installations of PV
connections with load-side taps.
John Wiles articles at New Mexico State University
can be found at:
Solar Ready Residential Service Panel
The photo shows a Siemens "solar
ready” service panel which is produced as a response to the need for easier
connections with PV systems.
This panel design constitutes a
line-side tap. A separate set of busbars, rated at 60 amps, is supplied for
connecting to an inverter with a set of breakers. That set of busbars is
connected directly to the load side of the meter socket before the main
disconnect, bypassing the main busbars altogether. This also bypasses all the difficulties
involved with load-side connections.
Since the line-side tap
connection is integral with the equipment and a part of its listing, it avoids
the problem of violating the listing of a panel by connecting a line-side tap
where the equipment is not approved for such use. But it will be a long time
before significant numbers of such panels are installed; and, meanwhile, the
majority of PV installations will be done on older service panels that were not
designed for the use.
With effective application of
existing code provisions, those panels can be safely utilized with PV while we
make the decades-long transition to equipment designed for the purpose. But 20
years from now, you’ll still see someone trying to do a line-side tap into a
rusty Zinsco 100-amp service at the meter socket, because there is no room for
more breakers and the owners would rather spend their cash on granite
countertops than a nice shiny new service panel.
Jeff Greef is a combination inspector with the City
of Cupertino in Silicon Valley, California.
Posted By Leslie Stoch,
Monday, September 16, 2013
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The Canadian Electrical Code Part I is a voluntary standard for adoption and enforcement by Canada’s provinces and territories, with provincial and territorial amendments. We rely on the CEC to provide safety standards for installation of electrical wiring and equipment. Its stated purpose is preventing electrical fire and shock hazards. But not all of its requirements are between its covers. Sometimes, we must get into other publications to obtain more complete information. This article reviews some examples.
Rule 12-012 provides, in great detail, the CEC requirements for installing high and low voltage underground conductors and their allowable ampacities (Table 53). At the end of this lengthy rule we find Rule 12-012(13) which advises us, that when an installation falls outside the scope of this rule, we must go to the underground standard, CAN/CSA-C22.3 No. 7. Reference to that standard brings its applicable parts into the CEC.
Rule 36-300 and Table 51 provide minimum grounding conductor requirements for substations over 750 volts for minimum copper wire sizes based on the available short-circuit current and fault current duration. A footnote to Table 51 indicates that wire sizes have been calculated using the IEEE Guide for Safety in AC Substation Grounding, ANSI/IEEE Standard No. 80. Table 52 provides maximum step and touch voltages in and around substations for several types of earth. You will note that a footnote to this table once again specifies that its values have been calculated using ANSI/IEEE Standard No. 80.
Rules 36-304 and 36-306 stipulate that maximum substation ground resistance for stations over 7500 volts must be calculated, based on available fault current levels and earth resistivities. Appendix B identifies the CEA Research Report 249-D-541 as the approved method of working out substation grounding electrode design. That document in turn references ANSI/IEEE Standard No. 80, which contains all of the formulae necessary for controlling step and touch voltages and conformance to Table 52.
Rule 32-200 requires that fire pump conductors be protected against fire exposure and to provide continued operation in compliance with the National Building Code of Canada. The rule refers us to Appendix B which elaborates on the rule — when called upon, fire and life safety systems must continue to operate for at least one hour. Checking Appendix B, we note it makes reference to NFPA Standard No. 80 as a further source of information for installation of fire pump wiring.
Rule 36-108 and Table 31 list minimum horizontal spacings between overhead conductors on pole lines for voltages up to 69 kV. A Table 31 footnote shows that the table does not cover voltages over 69 kV and pole spans greater than 50 m. For that information, we are referred to the CSA overhead lines standard CAN/CSA-C22.3 No. 1.
Rule 36-110 and Table 32provides vertical clearances for live parts up to 230 kV for indoor and outdoor substations for areas accessible only to pedestrians and areas accessible to vehicles. The vertical outdoor clearances are based on location — whether the substation is in a light or heavy snow area of the province or territory. Appendix B tells us that this information should be obtained from the Meteorological Service of Canada, Environment Canada, or the Atlas of Canada published by Natural Resources Canada.
Rule 18-000is the scope paragraph of Section 18 – Hazardous Locations. This rule refers to Appendix B which displays a long list of documents affecting the design of hazardous locations containing explosive gas atmospheres, combustible dusts or ignitable fibres. Appendix B shows 3 tables listing the applicable reference publications:
Table A – Documents generally applicable to all classes of hazardous locations.
Table B – Documents applicable specifically to Class I hazardous locations.
Table C – Documents Applicable specifically to Class II hazardous locations.
As you already know, the Canadian Electrical Code does not stand alone. As with previous articles, you should always check with the electrical inspection authority in each province or territory for a more precise interpretation of any of the above.
Read more by Leslie Stoch
Posted By Joseph Wages, Jr.,
Monday, September 16, 2013
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Fountains and reflection pools have been around for generations and make powerful statements and reminders of events that occurred at these locations. Beautifully built and constructed throughout the world, these locations are often works of art.
Photo 1. McKinney, Texas
On April 19, 1995, at 9:03 a.m., a tremendous explosion destroyed the Alfred P. Murrah Federal Building in Oklahoma City and 168 people lost their lives; but as a country, we lost much more. No longer could we take for granted that something like this could never happen again. As a people, we would always wonder when it would again. We looked at our children differently and gave them extra hugs. Things could never be the same again.
Photo 2. Oklahoma City Memorial
This happened in Middle America or what some consider Flyover country, and would leave its mark on the country as one of the worst domestic acts of terrorism to date. Many years later in 2001, the events known as "9/11” and the collapse of the Twin Towers would change this image and result in war.
Today, a reflection pool is part of the Oklahoma City Memorial, a solemn reminder of those events that allows the visitor to see his or her reflection as "someone changed by the events of that day.”
This destructive act took place roughly two hours from my home. Being a father, the loss of children weighed heavily on my heart. As a visitor to the site, I recall, my emotions were all over the place. I had gone as part of a group of men attending a Promise Keepers Rally held in the downtown area. It seemed that thousands stopped at the fountain to reflect on the events, to honor the victims, and to remember that which is important in life. On that day, for me, life took on new meaning in a personal way.
As you can imagine, the National Electrical Codehas requirements that govern electrical installations at these locations. Certain tragedies are, unfortunately, unavoidable due to the ill will of others. We can certainly do our best, however, to minimize or prevent senseless disasters from occurring by enacting strong Code adherence and educating as to its importance.
Photo 3. Fountain, Hot Springs, Arkansas. Millions of people have visited the waters found in Hot Springs National Park. Throughout Hot Springs there are numerous fountains and bath houses. Some people claim the waters from the fountains have therapeutic properties; and many of them use water bottles to "capture” this water for drinking purposes. But be careful at the fountains; you will find out quickly that the water is hot, and on a cold day, one can view the steam as it rises and quickly disappears.
Article 680 Swimming Pools, Fountains, and Similar Installations
I remember seeing my first fountain as a small child. This fountain was located inside the AQ Chicken House in Springdale, Arkansas. My mom would take us there when we would visit her brothers and sisters, and I would always ask for pennies to throw into the water. As I look back, this was an innocent time where wishes could be made with an expectation that they might happen. I can say that I never got any taller or got a chance at the NBA; but the fountain got a little richer from all those pennies from wish-making kids! This article deals with the construction and installation of electrical wiring at these locations.
Article 680 deals with these and other similar areas, such as the locations listed below:
- Swimming, wading, therapeutic and decorative pools
- Hot Tubs
- Hydromassage Bathtubs
We also need to keep in mind that the term body of water, used throughout Part I, applies only to bodies of water detailed in the scope, unless it has been otherwise amended. In this article we are going to look specifically at fountains and reflection pools. To do so, we need to start at the definitions.
Definitions are important to any project. The definitions we are interested in reside in 680.2. It is interesting to see that a reflection pool is located in the definition of a fountain.
Fountain. Fountains, ornamental pools, display pools, and reflection pools. The definition does not include drinking fountains.
Pool. Manufactured or field-constructed equipment designed to contain water on a permanent or semi-permanent basis and used for swimming, wading, immersion, or therapeutic purposes. (2011 NEC)
The term fountainapplies also to: ornamental pools, display pools, and reflection pools. Think about your Koi Pond tucked in the corner of your back yard. Have you ever considered it an ornamental pool? What about a display pool? What exactly is displayed at these pools? Reflection pools are familiar to many people; not only the reflection pool in Oklahoma City but also the reflection pool at the site of the former Twin Towers in New York City.
Interestingly enough, the code-making panelshad to take action on drinking fountains in the 1999 NEC. Language was placed into the definition specifically stating that drinking fountains were not included in the definition of fountains. It also made it clear that Article 680 did not apply to drinking fountains. This leads one to speculate that maybe an AHJ could have been trying to enforce the requirements found in Article 680 towards the drinking fountain.
Photo 4. Fountain luminaire with cord. Overheating protection of the electrical equipment is necessary for electrical equipment that depends on submersion for safe operation. A low-water cut-off or other approved means shall be provided when the equipment is no longer submerged.
Article 680 Part V, Fountains
Part five is where we zoom in on the specific requirements for fountains. The provisions of Part I and Part V of the article shall apply to all permanently installed fountains as defined in 680.2. As one might expect, luminaires, submersible pumps, and other submersible equipment shall be protected by a ground-fault circuit interrupter, unless listed for operation at low voltage contact limit or less and supplied by a transformer or power supply that complies with 680.23(A)(2).
So, what is meant by the low voltage contact limitas discussed above? This definition was new for the 2011 NEC. Let’s review this term.
Low Voltage Contact Limit
A voltage not exceeding the following values:
(1) 15 volts (RMS) for sinusoidal ac
(2) 21.2 volts peak for non-sinusoidal ac
(3) 30 volts for continuous dc
(4) 12.4 volts peak for dc that is interrupted at a rate of 10 to 200 Hz
[Excerpt from 2011 NEC,680.2]
"The low voltage contact limit described in this definition is based on the wet contact limits specified in Tables 11(A) and 11(B) in Chapter 9. In prior editions of the Code, the use of isolated winding type transformers that provided a sinusoidal ac voltage not exceeding 15 volts was used as the low voltage operational threshold for underwater luminaires. Although the 15-volt limit in Article 680 was based on a transformer-type power supply, it applied to all low- voltage systems. Any luminaire operating at more than 15 volts was required to be protected by a ground-fault circuit interrupter.
"In addition to sinusoidal alternating current, this definition also identifies the maximum acceptable safe levels for other voltage systems. Depending on the system, this maximum level is either higher or lower than that considered safe for sinusoidal ac voltage. New technologies for underwater lighting that integrate power supplies other than the traditional isolated winding type transformer have been developed, and this definition and associated requirements in Article 680 ensure that those new power supplies can be safely integrated into the swimming pool environment.” [Excerpt from 2011 NEC Handbook]
Photo 5. Sign in fountain, Fort Worth, Texas
Luminaires, Submersible Pumps and Other Submersible Equipment
The operating voltage for luminaires and submersible pumps and other submersible equipment is different. The operating voltage for supply circuits for luminaires shall not exceed 150 volts between conductors. The operating voltage for submersible pumps and other submersible equipment shall not exceed 300 volts or less between conductors.
Luminaires shall be installed in specific locations within these environments. Unless listed for above-water locations, the top of the lens shall be below the normal water level of the fountain. In the event that the lens is facing upward, it is to be adequately guarded to prevent contact by any person, or it is to be listed for use without a guard.
Nice to Know Info
Maximum Water Level. The highest level that water can reach before it spills out.
Note: Normal water level is different in each and every situation. As you might think, to define such a level would be impractical as each fountain or reflecting pool will be different. Therefore, it is recommended that you discuss the normal water level with the designer of the fountain before the project begins.
There is nothing that requires the installation of a luminaire in a pool of water; it is done by choice. Many luminaires are installed for aesthetic purposes to add to the enjoyment and tranquil feeling one might experience at the locations. Most generally, luminaires accentuate features found at that location.
The equipment located in fountains shall contain provisions for threaded conduit entries or shall be provided with a suitable flexible cord as required by 680.51(E). A maximum limit of 3.0 m (10 ft) has been mandated for the exposed cord within the fountain. Any cord located on the perimeter of the fountain shall be enclosed in an approved wiring method. An approved corrosive-resistant metal shall be used when metal parts are in contact with water. An example of a metal part that meets this requirement is brass.
Photo 6. Fountain in downtown Kansas City, Missouri
Equipment servicing is an important consideration when installing pool equipment. All equipment shall be removable from the fountain. This will allow for relamping of luminaires and for normal maintenance of equipment. Luminaires cannot be permanently embedded into the fountain structure so that water has to be removed or the fountain has to be drained in order to service the luminaires and equipment. All equipment that is to be part of a fountain shall be securely fastened in place or shall be inherently stable.
Nice to Know Info
What does "inherently stable” mean?
Inherent stability is often found throughout the aviation industry. It is the tendency of an aircraft to return to straight and level flight, when the controls are released by the pilot. Most aircraft are designed with this in mind and are said to be "inherently stable.” I guess that when applied to pool equipment, the equipment should return to its previous location and remain stable. Might there be an aviation guru involved with the NFPA process that got this term used here as well?
Receptacle Outlets Adjacent to Fountains
Fountains contain water. Water and electricity typically do not play well together. When we consider receptacles near fountains, we must keep this in mind. Ground-fault protection of these devices is necessary to ensure the safety of the user of the fountain. Any receptacle located within 6.0 m (20 ft) of the edge of the fountain shall be provided with GFCI-protection. This information can be found at 680.58.
Always remember to review the requirements for placement of equipment and other items associated with fountains. Code language dictates that the measurement for this equipment shall be made from inside the pool wall. Other code language from Article 680 for other situations will direct the installer to take the measurement from the outside of the pool wall. This requirment is located in 680.34. A slight oversight in reading and understanding these different requirements could be crucial to your receiving the final inspection results that make you happy.
Some fountains will be designed with signs in mind. Signs can take on many forms and fashions. The NEC deals with electric signs so not all signage will be affected by this language. Electric signs installed within a fountain or within 3.0 m (10 ft) of the fountain’s edge will be discussed next. Section 680.57(C) directs that "a fixed or stationary electric sign installed within a fountain shall be not less than 1.5 m (5 ft) inside the fountain measured from the outside edges of the fountain.”
In the event the sign is portable, we have two restrictions: (1) it shall not be placed within a pool or a fountain; and (2) it cannot be placed within 1.5 m (5 ft), measured horizontally, from the inside wall of a fountain.
A sign shall be grounded and bonded in accordance with 600.7. A disconnecting means conforming with both 600.6 and 680.12 shall be provided for a sign used with fountains.
Boxes and Enclosures
Boxes and enclosures are very important in a wet or damp location. These items will need to conform to 680.24 when used at a fountain. Each will need to be provided with threaded conduit entries or compressed glands and seals for cord entry. If the box or enclosure is to be submersible, it shall be constructed of copper, brass, or another approved corrosion-resistant material.
Section 680.52(B)(2)(a) requires a potting compound to prevent the entry of moisture for an underwater enclosure. The box or enclosure shall be firmly attached, per 680.52(B)(2)(b), to the fountain surface. If the box or enclosure is supported solely by conduits, the conduit shall be of copper, brass, stainless steel or another type of corrosion-resistant metal. Support shall be in accordance with 314.23(E) and (F).
Bonding and Grounding of Fountain
Do not take for granted the importance of grounding and bonding, which cannot be stressed enough in the installation process for the fountain. Bonding requirements are located at 680.53. The Informational Note further directs you to 250.122 for the sizing of these conductors that are attached from the metal piping systems to the equipment grounding conductor of the branch circuit.
Some equipment must be grounded. In 680.54, we find guidance that helps with this process. All electrical equipment — other than listed low-voltage luminaires not requiring grounding — located within the fountain or within 1.5 m (5 ft) of the inside wall of the fountain must be grounded. This also includes electrical equipment associated with the circulating system of the fountain, regardless of its proximity to the fountain.
Methods of grounding are discussed at 680.55(A). There are six code references that have applicable provisions for the fountain or reflection pool. In the event you have equipment supplied by a flexible cord, 680.55(B) needs to be consulted. All exposed non–current-carrying metal parts of electrical equipment that is supplied by a flexible cord shall be grounded by an insulated copper equipment grounding conductor that is an integral part of this cord. It shall be connected to an equipment grounding terminal located at the supply junction box, transformer enclosure, power supply enclosure, or other enclosure.
Cord- and Plug-Connected Equipment
We can’t escape cord- and plug-equipment. For guidance on installation practices, turn to 680.56(A) through (D). Maintenance of electrical equipment dictates that the power supply cords allow for this type of flexibility. Hence, all power supply cords shall be protected by ground-fault circuit interrupters.
There are also requirements that dictate the choice for cord types when used in fountains and reflection pools. If immersed in or exposed to water, a flexible cord shall be of the extra-hard usage type. This is typically designated in Table 400.4. The flexible cord shall also be a listed type with a "W” suffix.
A suitable potting compound is required for the end of the flexible cord jacket and for the flexible cord conductor that are intended to terminate within the equipment. This will prevent the entry of water into the equipment through the cord or its conductors. To prevent deteriorating effects from the water that may enter into the equipment, the ground connection shall be treated as well.
All flexible cord terminations shall be permanent, except for devices that need to be removed for maintenance, repair, or storage. This could include grounding-type attachment plugs and receptacles. Some of this equipment will be removed for storage and protection from the elements. Fountains are located at inside and outside locations throughout the world. In the event of freezing conditions, some of the equipment could be ruined. Removal of these items is essential to protect the equipment from these weather-related effects.
Photo 7. Spiritual Fountain, McKinney, Texas
I did not install the electrical equipment or inspect the fountain where I currently live. I am taking for granted that each person involved with this project has installed it as prescribed by the rules found within the National Electric Code. I think that if we all remembered how it could affect the end user, we would always have code-compliant projects. As stated earlier, water and electricity do not play well together. Enter a human life and things could go horribly wrong. It does not take a misguided individual blowing up a building to affect our daily lives; an unintentional mistake or oversight can have the same effects. Code requirements are important. Electrical installers are important. Electrical inspectors are important. Your loved ones are important to you! Who knows when they might visit or get into that pool!
Read more by Joseph Wages, Jr.
Posted By Steve Douglas,
Monday, September 16, 2013
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What are the criteria for connecting more than one motor on a single branch circuit overcurrent device?
To start to answer this question we need to re-visit the Canadian Electrical Code Part I (CE Code) definition of a branch circuit to recognize that a motor branch circuit is the circuit between the final overcurrent device and the motor including the conductor and the motor controller. In accordance with the CE Code the motor branch circuit conductors, controllers, and motors require short circuit protection in the form of an overcurrent device and motor requires overload protection.
Let’s start with the overload protection which is unique to a motor only.
The overload protection for the motor is designed to protect the motor in the event the motor is overloaded. The overload protection can be in the form of inherent overheating protection such as thermal protection (thermally protected or tp) or impedance protection (impedance protected or zp) as detailed in CSA Standard C22.2 No 77 Motors with Inherent Overheating Protection. A motor recognised as a motor with inherent overheating protection must be marked on the motor. (See photos 1 and 2).
Photo 1. A motor marked with inherent overheating protection
Photo 2. A motor that does not have inherent overheating protection
Other than the limited motors less than 1HP identified in CE Code Rule 28-308, motors not provided with inherent overheating protection will require remote overload protection. The setting of this overload protection is detailed in CE Code Rule 28-306. Motors with a service factor 1.15 and greater require the overload protection set at 125% of the motor full load ampacity and 115% for motors with a service factor less than 1.15. (See photo 3).
Photo 3. A motor nameplate where we can see the service factor (SF) of 1.15.
Remote overload protection can be provided by time delay fusing, overload relays, or other overload devices certified to CSA Standard C22.2 No 14 Industrial Control Equipment. (See photo 4).
Photo 4. Motor overload relay for a motor that does not have inherent overheating protection
With the overload dealt with, we can now focus on the short circuit protection requirements. The traditional method to provide short circuit protection is by the installation of overcurrent devices such as fuses or circuit breakers with an ampacity rating based on CE Code Table 29. As an example, the short circuit protection (overcurrent protection) required for a synchronous motor is limited to 175% of the motor full load ampacity for time delay fuses, 300% for non-time delay fuses and 250% for circuit breakers. Such limitations are intended to allow the motor to start without operating the overcurrent device during normal operation of the motor.
In the uncommon event these ratings of protection do not allow the motor to start because the motor inrush current is too high, CE Code Rule 28-200(d) allows the overcurrent protection to be further increased to 225% of the motor full load ampacity for time delay fuses, and (400% for motor up to 100 FLA and 300% for greater than 100 FLA) for circuit breakers.
Another method to provide short circuit protection is by using self-protected combination motor controllers also known as Type E or Type F combination motor controllers. CSA Standard C22.2 No 14 defines these controllers as:
A combination motor controller having non-replaceable or integral discriminating overload and short circuit current sensors, and provided with one or more sets of contacts where the contacts cannot be isolated for separate testing, shall be considered a Type E. (See photos 5A and 5B).
Photo 5A. Two Type E self-protected combination motor controllers. Photo 5B. The nameplate for one of the Type E self-protected combination motor controllers shown in Photo 5A. Note the accessories identified on the nameplate marking that must be installed before the controller can be accepted as a Type E self-protected combination motor controller.
A Type F combination motor controller is comprised of a magnetic or solid state motor controller coupled with a Type E controller. (See photos 6A and 6B)
Photo 6A. A Type F combination motor controller. Photo 6B. The nameplate for Type F combination motor controllers is shown in Photo 6A. Note the accessories identified on the nameplate marking that must be installed before the controller can be accepted as a Type F combination motor controller.
Type E and Type F self-protected combination motor controllers provide a disconnection means, short-circuit protective device, motor controller, and overload protection.
Another method to install multiple motors on a single branch circuit is with a controller marked suitable for motor group installation in conjunction with a main branch circuit overcurrent device (fuse of circuit breaker). (See photo 7).
Photo 7. A motor controller marked suitable for motor group installation
Precautions must be considered when grouping motors on a single branch circuit. The first precaution to consider is the markings on the controller for such group installations. CSA Standard C22.2 No 14 requires the maximum overcurrent protection to be marked on the controller. (See photo 8).
Photo 8. The maximum overcurrent protection that can be installed ahead of the group installation controller.
The second precaution to consider is the requirements of CE Code Rule 28-206. This rule directs code users to Rule 28-204 to limit the maximum overcurrent protection that can be installed ahead of the group installation controller.
For a feeder supplying motor branch circuits only, the ratings or settings of the feeder overcurrent device shall not exceed the calculated value of the overcurrent device permitted by Rule 28-200 for the motor that is permitted the highest rated overcurrent devices of any motor supplied by the feeder, plus the sum of the full load current ratings of all other motors that will be in operation at the same time.
As an example let’s look at a motor group installation consisting of five synchronous motors with full load ampacities (FLA) of 21, 2, 4, 7, 7, 7, and 16 A, and a main breaker installed ahead of the controllers marked suitable for group installation. (See table 1).
CE Code Rule 28-206 limits the circuit breaker ahead of the group installation to a maximum of 93 A 21x2.5=52.5 = 50 Amp breaker + (2+4+7+7+7+16). Note: the marking on the controller for Motor 2 limits the main circuit breaker to 80 A. As a result, this example for is not code-compliant. One option is to replace the Motor 2 controller with a group installation controller marked for a maximum 125 A circuit breaker and ensure the main breaker is not larger than 125 A.
The third precaution is the size of the circuit conductors including the tap conductors. The tap conductors are the conductors installed between the group installation controllers and the motors. CE Code Rule 28-106(3) limits the size of the tap conductor to not less than 1/3 that of the larger branch circuit conductor for the group of motors.
The minimum allowed ampacity of the branch circuit conductors for the group of motors in this example is 69.25 A, 21x1.25 + (2+4+7+7+7+16). From the 75⁰C column of CE Code Table 2, a 4 AWG copper conductor with the ampacity of 85 A has been selected. The following table shows the tap conductor sizes and percentages of the larger conductor for our example. (See table 2).
As you see, the Motors 2 to 6 have 14 AWG copper conductors with an allowable ampacity of 20 A that is less than 1/3 of the larger 4 AWG copper conductor allowable ampacity of 85 A. This can be made code-compliant by installing 12 conductor in place of the 14 AWG copper conductors, or separating the largest motor from the group reducing the main circuit breaker and larger conductor size. The following table shows the revised group without Motor 1. This group would now have a maximum main circuit breaker of 70 A, 16x2.5 = 40 Amp breaker + (2+4+7+7+7) and a minimum conductor allowable ampacity of 47 A, 16x1.25 + (2+4+7+7+7). Resulting in a 8 AWG copper conductor as the larger conductor supplying the group installation controllers. (See table 3 ) .
The final precaution to consider is the length of the tap conductors. CE Code Rule 28-106(3) limits the length of the tap conductors to a maximum of 7.5 m. The following table shows our revised example detailing the tap conductor lengths proposed. (See table 4).
As you can see the length of the tap conductor for Motor 4 is not code-compliant. If the conductor cannot be rerouted to limit the length of the tap conductor to 7.5m, individual overcurrent would need to be installed ahead of the tap for Motor 4.
The limitations when grouping motors on a single overcurrent device include the method of motor overload protection, short circuit protection for the motor branch circuit conductors, controllers and motors, size of the tap conductors, and the length of the tap conductors. The overload protection can be in the form of integral protection for the motor or remote overload protection as part of the control equipment. The maximum overcurrent device used to provide the short circuit protection for the motor branch circuit conductors, controllers, and motors must not exceed the limitations of Rule 28-206 and cannot exceed the maximum rating permitted by the rating marked on the group installation motor controller. The motor tap conductors must have an allowable ampacity not less than 125% of the motor full load ampacity. The motor tap conductor allowable ampacity must also be greater than 1/3 that of the larger conductor installed ahead of the group installation motor controller, and the maximum length of the motor tap conductor cannot exceed 7.5m.
Read more by Steve Douglas
Posted By Jesse Abercrombie,
Monday, September 16, 2013
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If you own a business, you may well follow a "do it now” philosophy; which is, of course, necessary to keep things running smoothly. Still, you also need to think about tomorrow, which meansyou’ll want to take action on your own retirement and business succession plans.
Fortunately,you’ve got some attractive options in these areas. For example, you could choose a retirement plan that offers at least two key advantages: potential tax-deferred earnings and a wide array of investment options. Plus, some retirement plans allow you to make tax-deductible contributions.
In selecting a retirement plan,you’ll need to consider several factors, including the size of your business and the number of employees. If your business has no full-time employees other than yourself and your spouse, you may consider a Simplified Employee Pension (SEP) plan or an owner-only 401(k), sometimes known as an individual or solo 401(k). Or, if your goal is to contribute as much as possible, you may want to consider an owner-only defined benefit plan.
If you have employees, you might want to investigate a SIMPLE IRA or even a 401(k) plan. Your financial advisor, working with plan design professionals and your tax advisor can help you analyze the options and choose the plan that fits with your combined personal and business goals.
Now, let’s turn to business succession plans. Ultimately, your choice of a succession plan strategy will depend on many factors, such as the value of your business, your need for the proceeds from the sale of the business for your retirement, your successor, and how well your business can continue without you. If your goal is to keep the business within the family,you’ll need to consider how much control you wish to retain (and for how long), whether you wish to gift or sell, how you balance your estate among your heirs, and who can reasonably succeed you in running the business.
Many succession planning techniques are available, including an outright sale to a third party, a sale to your employees or management (at once or over time), or the transfer of your business within your family through sales or gifts during your life, at your death or any combination thereof.
Many succession plans include a buy-sell agreement. Upon your death, such an agreement could allow a business partner or a key employee to buy the business from your surviving spouse or whoever inherits your business interests. To provide the funds needed for the partner or employee (or even one of your children) to purchase the business, an insurance policy could be purchased.
Your estate plan — including your will and any living trust — should address what happens with the business, in case you still own part or all of it at your death. The best-laid succession plans may go awry if the unexpected occurs.
All these business succession options can be complex, so before choosing any of them, you will need to consult with your legal and financial advisors.
Whether it’s selecting a retirement plan or a succession strategy,you’ll want to take your time and make the choices that are appropriate for your individual situation.
You work extremely hard to run your business, so do whatever it takes to help maximize your benefits from it.
Read more by Jesse Abercrombie
Posted By David Clements,
Monday, September 16, 2013
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It seems that every time we turn the television on or check our mobile device we hear about a disaster: floods, tornadoes, wild fires and explosions. I recall, in 1992 while living in Nova Scotia, how an explosion at the Westray coal mine located in a small community of Plymouth, Nova Scotia, claimed the lives of 26 miners. The bodies of those miners were never recovered and remain deep within the mine. Justice Peter Richard in his report on the explosion and fire said, "The Westray story is a complex mosaic of actions, omissions, mistakes, incompetence, apathy, cynicism, stupidity and neglect.”
His report also cited safety abuses, among them, inadequate ventilation design and maintenance to keep methane and coal dust at safe levels; methane detectors that were disconnected because of frequent alarms; procedures to "stonedust”1 coal to render it non-explosive, which were done sporadically, usually before inspections; and an "appalling lack of safety training and indoctrination” of miners.
On April 17, 2013, an ammonium nitrate explosion occurred at the West Fertilizer Company storage and distribution facility in the town of West, Texas, killing 15, injuring more than 160, and causing property damage in the millions. The authorities have yet to determine the cause.
With any major disaster, some are preventable and others are not. An investigation is conducted into the cause, reports are filed, and recommendations are made. In many cases, it is determined that either there was a lack of regulations, standards or compliance. What lessons are learned?
In June of this year I attended the National Fire Protection Association (NFPA) Annual Expo and Conference held in Chicago, Illinois, and the Canadian Standards Association (CSA) Annual Conference held in Calgary, Alberta. At these meetings, experts in their field voted on changes that will be incorporated in the next edition of the National Electrical Code (NEC) and in Canadian Electrical Code, Part 1 (CEC).
I witnessed the passion and commitment individuals representing their organizations had towards developing new requirements ensuring products and installations are safe from fire and shock hazards. The development of these standards is based on a balanced matrix of industry professionals and through a consensus process. IAEI technical committee members play a major role in this consensus process as they bring forth the inspectors’ perspective and knowledge.
These groups and individuals understand the value of standards. However, there are still cynics out there who are not part of the code development process that believe we are overregulated, and who feel that changes are made in the codes only to benefit manufacturers and that costs outweigh the safety benefits. We saw this when GFCIs were first introduced, and we are now seeing the same argument with AFCIs.
So do these cynics understand the value of standards — that standards help streamline process, and provide rules, guidelines and instructions for producing predetermined results? Without electrical standards would you feel safe in your home?
We have a responsibility and due diligence to ensure standards are developed and revised when problems, gaps and new products are identified. However, one cannot rely on standards alone to ensure that a product or installation is completely safe. It requires a systematic approach which includes four components: (1) applying current electrical standards (NEC) and (CEC); (2) installations performed by qualified installers; (3) third party certification of products; and (4) enforcement by qualified electrical inspectors.
So never underestimate the importance and tangible benefits of implementing the systematic approach.
William Blake, English poet, said, "What is now proven was once only imagined.” Hindsight is a wonderful thing but foresight is better, especially when it comes to saving life, or some pain!
1Stone dust (mining engineering) Inert dust spread on roadways in coal mines as a defense against the danger of coal-dust explosions; effective because the stone dust absorbs heat. McGraw-Hill Science & Technology Dictionary
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Read more by David Clements
Posted By David Clements,
Monday, July 01, 2013
Updated: Wednesday, June 19, 2013
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In the May-June issue, I talked about branding and how every little thing matters. What I didn’t talk about specifically was IAEI’s brand: Who we are.
Our mission statement states that we promote electrical safety throughout the industry by:
- Providing premier education
- Certifying inspectors
- Expert leadership in electrical codes and standards development
Historically, we know what IAEI was intended to be and the seven objectives we were expected to fulfill. We know also who we have become and the stories of triumph and trouble, fulfillment and failure, success and stagnation, autonomy and arrogance. We’ve seen it all because we’ve been around a long time — 85 years. However, the dream and the commission remain: to participate in making, promoting and enforcing standards for the safe use of electricity, both nationally and internationally.
But we have reached a fork in the road. This is a deciding moment in IAEI’s history when a major choice of options is required. We must decide two things: Who are we now? and Where do we want to go from here?
Sometimes we assume we know the answers to what appears to be an easy question. However, what the IAEI Board of Directors perceive and what I perceive the answers to be can differ from the perceptions of our members and from the electrical industry. So the fact is, it doesn’t matter how the Board or I perceive IAEI, what really counts are how our members, the public, and the electrical industry view us.
I could go out on a limb and give you my opinion, but I’ve been around enough not to assume I have all the answers. Yes, there are indicators which prove that we have character, credibility and reputation that extends back to the beginning of our organization. These indicators include positive comments from members, support from our industry partners who understand the importance and vital role that IAEI plays towards electrical safety, and requests we receive from reputable organizations that want to partner with us.
In order for IAEI to serve the current and future generations of the electrical industry, it is important that we step back to see the big picture and make sure we are working to improve and change with the wants and needs of the industry to benefit our brand, and to change our brand to benefit the industry itself. However, it’s not enough to be great at something or to be an expert in your field. The electrical industry is buying our bigger mission of promoting electrical safety, in many cases, first. This has to pervade and drive a brand’s messaging and actions no matter what the outlet we use— such as, meetings, seminars, media.
The strength of our association lies in our constancy to our mission and to our guiding objectives. Our success derives from us remaining relevant, credible and trustworthy. Our character rises from our avoiding the search for power that undermines and choosing instead the reputation of disseminating life-saving information.
So we start with who we are now, what the target mindset is and what the shared values are between them. We study, learn, and build how the IAEI’s brand (member community) and the nonmembers’ user journey collide in fortuitous ways to create action, conversation and conversion that cements them to the brand.
To take our quest to the next level, we asked our members and our industry partners, by survey, what was their perception of IAEI. Were we being true to our mission statement? Why did they want to be part of IAEI? How could we serve the electrical industry better? As soon as the results are available, we will share them with you.
By the way, Yogi Berra, catcher for the New York Yankees, said, "When you come to a fork in the road, take it.”
Follow Dave on Twitter @DavidEClements
Read more by David Clements
Posted By Leslie Stoch,
Monday, July 01, 2013
Updated: Wednesday, June 19, 2013
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This article will discuss seals. Not the cute furry ones, but the kind you need to reduce fire and explosion risks in locations containing flammable and explosive gases or vapours.
The Canadian Electrical Code, Section 0 defines the requirement for conduit seals — to prevent passage of an explosion from one portion of the conduit system to another and that minimizes passages of gases or vapours at atmospheric pressure. The last two words of this definition imply that less dangerous amounts of gases or vapours at higher than atmospheric pressure may pass through the seals.
A Class I Zone 1 location is one in which an explosive gas atmosphere may exist in normal operation. Rule 18-108 requires conduit seals in Class I Zone 1 hazardous locations where conduit enters an explosion-proof or flame-proof equipment enclosure within 450 mm (17.72 in.) of equipment that may produce sparks, arcs, or high temperatures. You will recall that explosion-proof and flame-proof enclosures are capable of withstanding internal explosions and preventing ignition of the specified gases or vapours surrounding the electrical equipment. Where the enclosures contain only terminals, taps or splices, conduit seals are required only for conduit trade size 53 or larger.
Conduit seals are necessary to prevent explosions from passing through the conduit and, importantly, from a classified hazardous to a non-hazardous location. To reinforce this requirement, Rule 18-108 specifies conduit seals where conduit leaves a Class I Zone 1 hazardous location with no boxes or fittings between each seal and the point where the conduit leaves the hazardous location.
Section 0 defines a cable seal as one installed at a cable termination to prevent the release of an explosion from an explosion-proof enclosure and that minimizes the passage of gases or vapours at atmospheric pressure. As discussed earlier, this implies that less dangerous quantities of gases or vapours at higher than atmospheric pressure may pass through the seals. Rule 18-108 requires that cable seals be provided in Class I Zone 1 hazardous locations where a cable enters an explosion-proof or flame-proof enclosure or terminates in a Zone I location. Only cables approved for hazardous locations must be installed.
Conduit and cable seals are also required to prevent pressure-piling. When an explosion occurs in hazardous location equipment without a conduit seal, due to presence of flammable gases or vapours inside the conduit, a series of internal explosions may occur along its length. Each subsequent explosion raises the pressure inside the conduit to the point where the equipment enclosure at the far end of the conduit may be destroyed. Pressure-piling can be prevented by sealing the conduit. Sealing of cables is also highly important since cables are not tested or designed to withstand an internal explosion.
Rule 18-000 defines a fluid as a substance in the form of gas, vapour or liquid. It defines a primary seal as a seal that isolates the process fluids from an electrical system, and that one side of the seal is in contact with the process fluid. For example, sealing of the wiring to a measuring device inside a pressurized pipeline or enclosed vessel at the point where the wiring exits the pipeline or vessel. Rule 18-072 specifies that primary seals are required to prevent migration of flammable fluids through the wiring system. As earlier indicated, conduit and cable seals are not designed to prevent passage of flammable fluids at higher than atmospheric pressure; therefore, the need for primary seals.
Rule 18-000 defines a secondary seal as a seal that is designed to prevent passage of process fluids upon failure of the primary seal. A secondary seal is installed between the primary seal and the conduit or cable seal to back up the primary seal in case the primary seal should fail to contain the process fluid. Rule 18-072 specifies that where a secondary seal is installed, failure of the primary seal must become obvious or marking that the pipeline or vessel may contain flammable fluid under pressure. Some secondary seals may include an alarm circuit to make a primary seal failure obvious.
As with previous articles, you should always consult the electrical inspection authority in each Province or Territory as applicable for a more concise interpretation of any of the above.
Read more by Leslie Stoch
Posted By Christel Hunter,
Monday, July 01, 2013
Updated: Thursday, June 20, 2013
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Electrical systems are typically given a great deal of consideration during the design and installation phase of new construction or major renovation, but very little thought after completion — until something fails. Even though our electrical systems are usually very reliable, it is likely that some components will need maintenance or testing at some point in the life of the building or structure. Therefore, the NEC contains requirements meant to allow for safe and practical access to electrical equipment after the time of installation.
In the NEC, working space requirements are found primarily in Article 110. NEC 110.26 applies to electrical equipment operating at 600 volts or less. The primary requirement is that both access and working space must be provided and maintained for all electrical equipment. (Photo 1). This is to allow for ready and safe operation and maintenance of the equipment.
Photo 1. Code violation of 110.26
The definition of equipment in the NECis "a general term, including fittings, devices, appliances, luminaires, apparatus, machinery, and the like used as a part of, or in connection with, an electrical installation.” This is a very broad definition, and when put in the context of working space requirements, likely includes many items not usually thought of when applying the requirements of 110.26.
After the first paragraph, Section 110.26 is divided into six subsections identified as (A) through (F). Section 110.26(A) defines the required height, width and depth of working space according to the voltage and type of equipment being considered. These requirements are specific to equipment "likely to require examination, adjustment, servicing, or maintenance while energized.”
Depth of working space is covered in 110.26(A)(1) and the associated table. The question is often asked, "Where do we start the measurement — from the live parts, the dead front, or the cover?” The NEC tells us that the measurement must begin from the exposed live parts, unless the live parts are enclosed. If they are enclosed, the measurement begins from the enclosure or opening.
Table 110.26(A) has three conditions for determining the minimum clear distance. (Figure 1). Condition 1 applies either when there are exposed live parts on one side of the working space and no live or grounded parts on the other side of the working space, or when there are exposed live parts on both sides of the working space that are effectively guarded by insulating materials. For Condition 1 installations with voltages to ground up to 600 volts, the minimum clear distance is 3 feet.
Condition 2 applies when there are exposed live parts on one side of the working space and grounded parts on the other side of the working space. The code explicitly states that concrete, brick or tile walls shall be considered as grounded. For Condition 2 installations with voltages between 0 and 150 volts, the minimum clear distance is 3 feet. For voltages between 151 and 600 volts, the minimum clear distance is 3.5 feet.
Condition 3 applies when there are exposed live parts on both sides of the working space. For this condition and voltages between 0 and 150 volts, the minimum clear distance is again 3 feet; while for voltages between 151 and 600 volts, the required distance is 4 feet.
Certain installations are allowed exceptions from the minimum depth requirements. For assemblies such as dead-front switchboards and motor control centers where all the connections and renewable or adjustable parts are accessible from locations other than the back or sides, there is no working space required for the back or sides of the equipment. If there are nonelectrical parts of such equipment that require rear access to work on them, a minimum horizontal working space of 30 inches is required.
Certain low voltage installations also have less required working space. If all the exposed live parts operate at not greater than 30 volts RMS, 42 volts peak, or 60 volts dc, then the inspector is allowed to grant special permission for a reduced working space. The definition of special permission in the NEC is "the written consent of the authority having jurisdiction,” so be sure to get it in writing! The specific amount of working space for these installations is not indicated, so it is up to the installer and the AHJ to work together to determine the safe amount of working space.
The NEC provides an allowance for existing buildings, as well. Where there are dead-front switchboards, panelboards, or motor control centers across an aisle from each other that are being replaced in an existing building, the Condition 2 distances are allowed instead of Condition 3. This only applies if there is maintenance and supervision of the building to ensure that written procedures have been adopted to: 1) prohibit equipment on both sides of the aisle from being open at the same time and 2) ensure that only authorized qualified persons are allowed to service the installation.
Width of working space is simpler to determine than depth; it is required to be the width of the equipment or 30 inches, whichever is greater. So if you have three 20 inch wide panelboards mounted on the same wall next to each other, what is the required working space? Since there is no prohibition against equipment sharing the width of working space, it could technically be as little as 60 inches. However, this is neither practical (for mounting reasons) nor prudent. It is a better practice to provide spacing between equipment and not to place a piece of equipment right up against a perpendicular wall, since this might make it more difficult to service in the future.
Remember that the requirements in the NEC are minimums; you are always allowed to make an installation safer and better. Note that the working space must also allow at least a 90 degree opening of equipment doors or hinged panels, so that might come into consideration depending on the design of the equipment.
Height of working space is measured from the grade, floor, or platform, and is required to be at least 6.5 feet or the height of the equipment, whichever is greater. If there is electrical equipment that is associated with the electrical system located above or below a piece of equipment, it is allowed to extend no more than 6 inches into the required working space.
There are two exceptions to the base requirement for height of working space. The first is for existing dwelling units, where panelboards, or service equipment, that do not exceed 200 amperes are allowed in working space that is less than 6.5 feet. (Quick fact: individual meter socket enclosures are not considered service equipment per 230.66.) The second exception is new to the 2011 NEC and states that meters that are installed in meter sockets shall be permitted to extend beyond the other equipment, but the meter socket is still required to follow the rules of this section. (Figure 2).
Moving on from the working space requirements, our next requirement is in 110.26(B) for clear spaces about electrical equipment. The required working space is not to be used for storage. No mops, no boxes, no stock, etc. As shown in photo 2, this is a commonly violated code rule. Additionally, if equipment is located in a passageway or general open space, it must be suitably guarded if any normally enclosed live parts are exposed for inspection or servicing.
The next few requirements cover entrance to and egress from the required working space. The minimum requirement is that at least one entrance of sufficient area must be provided. This is both to allow access to the equipment and egress from the working space about electrical equipment. Although "sufficient” is considered to be a "possibly vague or unenforceable” word in the NEC Style Manual, it is hard to think of a better word that would be inclusive of all the potential electrical equipment installations.
Large equipment has special requirements. For the purposes of these requirements, large equipment is defined as equipment rated 1200 amperes or more and over 6 feet wide that contains overcurrent devices, switching devices, or control devices. For this equipment, at least one entrance to and egress from the required working space is required at each end of the working space, and each entrance must be at least 24 inches wide and 6.5 feet high.
Photo 2. Code violation of 110.26(B)
There are two exceptions to the requirement for multiple entrance/egress points. The first is when there is a continuous and unobstructed path of egress; in that case a single entrance is permitted. For example, if the equipment is on the wall directly opposite an entrance door and there is nothing between the two, this may be permitted as the single entrance.
The second exception is when there is extra working space. (Figure 3). If the depth of working space is twice that required by 110.26(A)(1), a single entrance is permitted. The distance to the nearest edge of the entrance from the equipment must be not less than the minimum clear distance as specified in Table 110.26(A)(1), based on the voltage and condition present. The idea behind this exception is to allow enough space for the electrician to get far enough away from the equipment to avoid being trapped if there is a problem in the equipment between the electrician and the exit.
Personnel doors also have special requirements for installations with equipment rated 1200 amperes or more that contains overcurrent devices, switching devices, or control devices. If the door is intended for entrance to and egress from the working space and the door is less than 25 feet from the nearest edge of the working space, then the door has to open in the direction of egress. It must also have panic bars, pressure plates, or other devices that are normally latched but open under simple pressure. (Photo 3).
Photo 3. Example of personnel doors with appropriate opening hardware
Illumination is obviously important for anyone working on electrical equipment. The NEC requires that illumination be provided for all working spaces around service equipment, switchboards, panelboards, or motor control centers installed indoors. New for the 2011 NECis the specific requirement that this required illumination shall not be controlled by automatic means only. (Figure 4). If the working space is illuminated by an adjacent light source or as permitted by 210.70(A)(1), Exception No. 1 for switched receptacles, then additional lighting outlets are not required.
Switchboards, panelboards, and motor control centers must be located in dedicated spaces and protected from damage. The only exception to this rule is for control equipment that for some reason (either because of its use or other code rules) must be adjacent to or within sight of its operating machinery. There are separate code requirements for indoor and outdoor dedicated equipment space.
Indoor installations must comply with four conditions including rules for dedicated electrical space, foreign systems, sprinkler protection, and suspended ceilings. The dedicated space requirement states that an area equal to the width and depth of the equipment and extending from the floor to a height of 6 feet above the equipment or to the structural ceiling (whichever is lower) must be dedicated to the electrical installation. This prohibits piping, ductwork, leak protection apparatus, and any other equipment that is not associated with the electrical equipment from being located in this space.
Some foreign systems are allowed above the dedicated space, but only if protection is provided to prevent damage to the electrical equipment from condensation, leaks, or breaks in the foreign system. (Figure 5). Sprinkler protection is permitted for the dedicated space, as long as the piping does not enter the required dedicated electrical space and is protected against leaking.
Dropped, suspended, or similar ceilings that do not add strength to the building are not considered structural ceilings. Suspended ceilings with removable panels are permitted within the dedicated electrical space.
Electrical equipment installed outdoors must be installed in suitable enclosures and protected from accidental contact by unauthorized personnel, vehicular traffic, and accidental spillage or leakage from piping systems. All of the working space requirements in 110.26(A) still apply, and there is a further requirement that no architectural parts or equipment are allowed to be located in the working space.
The last section of 110.26 deals with locked electrical equipment rooms or enclosures. If an electrical equipment or room is locked, it is considered accessible to qualified persons. The definition of accessible(as applied to equipment) in Article 100 is "admitting close approach; not guarded by locked doors, elevation, or other effective means.” The language in 110.26(F) is a way to reconcile the requirement of 110.26 that access is to be provided to electrical equipment, while also allowing for locked rooms to protect equipment from unqualified persons.
There are additional requirements for equipment above 600 volts, including 110.32, 110.33 and 110.34. Many of the base requirements are very similar to those for equipment operating at 600 volts or less, and I encourage you to read those sections if you design, install or inspect equipment rated at higher than 600 volts.
It can seem difficult to find adequate space for electrical equipment due to construction limitations in new buildings or existing buildings; however, the working space requirements are necessary for the safety of maintenance personnel and service electricians. While it is always recommended to de-energize equipment before working on it, there are certain operations (especially testing) that require accessing live parts. The working space requirements provide adequate space for working safely on the equipment and for egress away from the equipment in the case of an abnormal condition.
Read more by Christel Hunter
Posted By Steve Foran,
Monday, July 01, 2013
Updated: Thursday, June 20, 2013
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Last summer my wife and I moved into a neighborhood close to where we both grew up. The deck railing on our new home was too low and took away from the appearance of the house. We decided to replace it with an updated railing system. We were looking for something a little different but not too extravagant, and within our budget. We found a creative young woodworker who specializes in unique projects.
After we hired him, the engineer came out in me. The craftsman and I had many conversations about various layouts, designs and the intricate details of making it all come together.
In one of the early discussions we identified a challenge in how the two rails would meet together in the corner. He hadn’t run up against this particular situation before and obviously, as an armchair deck builder, neither had I. We agreed to think about it and meet again the next day to make the final decision.
You know how your mind focuses when something captures your attention. Well, I was consumed by this problem. To me, it was an engineering challenge. On and off for the next 10 hours or so, I tried to visualize how to make it work. Then out of the blue, the solution came to me.
I sketched the design on a piece of paper. Yup, I figured it out! I was excited about having the answer and proud of unlocking the puzzle.
The next day at our progress meeting I began abruptly, "I figured out the corner thing.” I then went on to explain all the details of how to build the corners. I even told him how I came to the solution and how much time I spent thinking about it.
When I was done speaking, I looked at him and thought, "Oh my goodness, what have I done?” He had a polite, forced smile on his face. It was like I had taken the wind out of his sails.
I had not asked how he was doing or if he had any thoughts on how to tackle the problem. I was so focused on myself; I just dove headlong into my idea.
I realized that in my excitement I broke one of the cardinal rules in dealing with people. I acted in a way that did not appreciate his skills and abilities and in doing so slighted his dignity. My solution was right, but the way I was right was wrong. After I realized what happened, I apologized. He appreciated that and explained that he had not taken offense. Again, he was very generous.
My actions were not deliberate but that does not matter. If we expect people to give the best of themselves, we must acknowledge and honor the best in them. This begins by allowing people to use their gifts and talents and then by resisting the temptation to rescue someone at the first sign of a challenge, unless of course the risk of inaction demands you act. As difficult as it can be, you must recognize that "standing by” is sometimes necessary even when you have the answer or think you do.
Read more by Steve Foran