National Electrical Code Forum Your Questions Answered

Meet Your Distinguished Experts Moderator: Lloyd Osborn- Cheyenne, Wyoming

Tom Lichtenstein Republican Organizer-Chicago, IL

Tim McClintock NFPA Regional Representative-Wooster, OH

Marcus “Sam” Sampson Western Section 1st Vice President, CMP 15-St Paul, MN

Vince Saporita Cooper/Bussmann, CMP 10 & 11, NEC Correlating Committee-St Louis, MO

Phil Simmons Simmons Electrical Service, CMP 5-East Olympia, WA

Christine Porter Intertek Field Evaluator, CMP 5-Seatle, WA

1. Do the factory wings that many fluorescent troffers have designed to fold out

over the grid meet the requirements for “securely fastened to the framing”?

Reference: NEC 410.16(B)

Answer: No, 410.36(B) Requires as bolts, screws, or rivets or Listed clips identified

for use with the type of ceiling framing member and luminaire.

See FLUORESCENT RECESSED LUMINAIRES (IEVV) located on page 174 in the 2012

UL White Book. States Recessed luminaires intended for use in suspended

ceilings and provided with integral clips are marked for use with particular grid

systems.

Separate Clips Listed under Luminaire Fittings (IFFX) on page 187 in UL White Book

Recessed Fluorescent Troffer Securement

2) Is it a code violation to have general purpose receptacles on the same lighting circuit that has required battery backed up emergency lights

Reference: NEC® 700.12

Answer: No – 700.12 (in part): Last paragraph: • 700.12 General Requirements: Unit equipment in accordance with 700.12(F)

shall satisfy the applicable requirements of this article. • 700.12(F): Flexible cord-and-plug connection shall be permitted, provided

that the cord does not exceed 900 mm (3 ft) in length. • 700.12(F): The branch circuit feeding the unit equipment shall be the same

branch circuit as that serving the normal lighting in the area and connected ahead of any local switches.

Emergency Lights: Unit Equipment

Answer: No

Reference: 680.26(B)(2) Equipotential Bonding

and 250.52 Grounding Electrodes

3. Is it allowed to use the grounding grid of the pools patio as the grounding electrode system for a separate structure’s

pool equipment?

680.26 Equipotential Bonding

(A) Performance. The equipotential bonding required by this section shall be installed to reduce voltage

gradients in the pool area.

680.26 Equipotential Bonding

(B) Bonded Parts. The parts specified in 680.26(B)(1) through (B)(7) shall be bonded together using solid copper conductors, insulated covered, or bare, not smaller than 8 AWG or with rigid metal conduit of brass or other identified corrosion-resistant metal.

(2) Perimeter Surfaces. The perimeter surface shall extend for 1 m (3 ft) horizontally beyond the inside walls of the pool and shall include unpaved surfaces, as well as poured concrete surfaces and other types of paving.

680.26 Equipotential Bonding

680.26 Equipotential Bonding

250.52(A) Electrodes Permitted for Grounding

(1) Metal Underground Water Pipe in direct contact with the earth for 3.0 m (10 ft)

(2) Metal Frame of the Building or Structure in direct contact with the earth for 3.0 m (10 ft) or more

(3) Concrete-Encased Electrode at least 6.0 m (20 ft) encased by at least 50 mm (2 in.) of concrete

(4) Ground Ring at least 6.0 m (20 ft) of bare copper conductor at a depth not less than 750 mm (30 in.)

(5) Rod and Pipe Electrodes not be less than 2.44 m (8 ft) in length

(6) Other Listed Electrodes Man-made…

(7) Plate Electrodes not less than 0.186 m2 (2 ft2) of surface to exterior soil

(8) Pool perimeter equipotential bonding grid

3. Is it allowed to use the grounding grid of the pools patio as the grounding electrode system for a separate structure’s

pool equipment?

Answer: No

4. A 3-phase 120/208-volt generator nameplate shows the rating to be 275KW and 285KVA. The load calculation by the engineer shows the load on the generator to be 790-amperes. Is this acceptable?

Reference: Article 445 Generators, 110.3(B)

Answer: There is nothing in Article 445 that limits a generator to 80% of its rating. Therefor it can be utilized at 100% of its rating. 285,000/(1.732X208) = 791.1 amperes = FLA of generator. The load on the generator is 790 amperes. Therefore, this is acceptable.

Generator/ Loading

5. 2011 NEC 250.32 Buildings or Structures Supplied by a Feeder(s) or Branch

Circuit(s) requires that an EGC be installed with the feeder conductors and

bonded to the subpanel in the outbuilding. In addition, a GEC is to be

installed to all available electrodes at the separate structure. If there are no

available electrodes and a ground rod is driven and an appropriately sized

GEC installed, is it required that this ground rod be supplemented as required

in 250.53(A)(2) or can the one ground be considered supplemented by the

main electrode system using the EGC to bond them together

Reference: NEC 250.32; 250.53(A)(2)

Answer: Treat each building or structure as an “Island” so far as grounding

electrode systems are concerned. Two ground rods are required at the

building or structure supplied by a feeder unless a single rod meets the 25

Ohm rule in 250.53(A)(2) Exception.

Grounding & Bonding, More than One Bldg

PVC expansion fittings

6) A 200 ampere, 277/480 volt feeder is installed in 50 feet of 2½", Schedule 80, PVC Rigid Nonmetallic Conduit on the south side of a steel building. During the winter months, the outdoor temperature differs by as much as 50 degrees (°F). How much will the conduit expand in length with this change of temperature? And would an expansion type of fitting be required?

Reference: NEC® 352.44 and Table 352.44

Answer: 1.015 inches, and YES fitting is required

• A fitting is to be used whenever the length change is expected to be equal to or greater than 6mm (1/4”)

• Straight runs between anchored points

• No difference between Schedule 40 & Schedule 80 conduits

Table 352.44 (in part) 6) continued

7. Is it permissible to install compact fluorescent lamps in existing 6-inch recessed luminaires?

Reference: 110.3(B)

Answer: Yes, see Self Ballasted Lamps and Lamp Adapters (OOLR) on page 278 in the 2012 UL White Book.

The OOLR Guide Information states These products

have been investigated for use in the smaller of a

6- or 8-in. diameter, totally enclosed, recessed

luminaire, if they will physically fit, unless marked

not for use in a totally-enclosed luminaire.

Compact Fluorescent Lamps

PVC expansion fittings

6) A 200 ampere, 277/480 volt feeder is installed in 50 feet of 2½", Schedule 80, PVC Rigid Nonmetallic Conduit on the south side of a steel building. During the winter months, the outdoor temperature differs by as much as 50 degrees (°F). How much will the conduit expand in length with this change of temperature? And would an expansion type of fitting be required?

Reference: NEC® 352.44 and Table 352.44

Answer: 1.015 inches, and YES fitting is required

• A fitting is to be used whenever the length change is expected to be equal to or greater than 6mm (1/4”)

• Straight runs between anchored points

• No difference between Schedule 40 & Schedule 80 conduits

GFCI Requirements for Basements

8) A basement is finished except for the concrete floor which remains original. Is GFCI protection required for all 120volt outlets in this area?

8) A basement is finished except for the concrete floor which remains original. Is GFCI protection required for all 120volt outlets in this area?

Reference: NEC® 210.8(A)(5) & 90.4

Answer: • 210.8 requires ground-fault circuit-interruption for personnel shall be provided

as required in 210.8(A) through (C). • 210.8(A)(5) Unfinished basements — for purposes of this section, unfinished

basements are defined as portions or areas of the basement not intended as habitable rooms and limited to storage areas, work areas, and the like.

• GFCI protection would be an AHJ call for the receptacle outlets located in this

basement. The term “unfinished” first appeared in the 1990 NEC. CMP 2 formulated a panel statement in Comment 2-647 of the 1989 TCR that stated “Determination of whether a basement is “finished” or “unfinished” is subject to the authority having jurisdiction”.

GFCI Requirements for Basements

9. A hot tub is surrounded by a wooden fence with metal poles that are within 5’ of the water’s edge.

Do all of the metal poles within the 5’need to be to be bonded to the equipotential bonding grid?

Reference: 680.26(B)(7) Answer: Yes

680.26 Equipotential Bonding

(A) Performance. The equipotential bonding required by this section shall be installed to reduce voltage gradients in

the pool area.

680.26 Equipotential Bonding

(B) Bonded Parts. The parts specified in 680.26(B)(1) through (B)(7) shall be bonded together using solid copper conductors, insulated covered, or bare, not smaller than 8 AWG or with rigid metal conduit of brass or other identified corrosion-resistant metal.

680.26 Equipotential Bonding

(B)(7) Fixed Metal Parts. All fixed metal parts shall be bonded including, but not limited to,

metal-sheathed cables and raceways, metal piping, metal awnings, metal fences, and metal door and window frames.

9. Do all of the metal poles within the 5’need to be to be bonded to the equipotential bonding grid?

Answer: Yes

10. Can two outside breakers of adjacent four pole, common trip, breakers be utilizes as a common trip breaker, for 240 volt loads, if they are tied with an approved handle tie?

Reference: 240.15(B)(1) & (2)

Answer:

No. 240.15(B)(1) states that “Individual single-pole circuit breakers, with identified handle ties, shall be permitted as the protection for each ungrounded conductor of multi-wire branch circuits that serve only single-phase line-to-neutral loads.” These are not single pole circuit breakers, therefore, handle ties are not allowed.

Circuit Breakers/ Handle Ties

11. Is an equipment bonding jumper required between a cable tray and free standing switchgear when uncoated type MC cables drop from the tray to the switchgear?

Reference: NEC 392.60(C)

Answer: Yes, a bonding jumper is required. It is to be sized in accordance with 250.102.

250.102(C) Supply-Side Bonding Jumper applies if there is no overcurrent protection on the supply side.

250.102(D) Equipment Bonding Jumper on Load Side of an Overcurrent Device applies if there is overcurrent protection on the supply side.

Bonding Jumper Required?

T-Grid Mounting of Outlet Boxes 12) Does the NEC allow a 4” square box for t-grid lighting

fixture branch Circuit conductor to be attached to the t-grid if a support bracket made for this purpose

Reference: NEC® 314.22(D)

Answer: Yes - 314.22(D) (in part)

(D) Suspended Ceilings. An enclosure mounted to structural or supporting elements of a suspended ceiling shall be not more than 1650 cm3 (100 in.3) in size and shall be securely fastened in place in accordance with either (D)(1) or (D)(2).

(1) Framing Members. An enclosure shall be fastened to the framing members by mechanical means such as bolts, screws, or rivets, or by the use of clips or other securing means identified for use with the type of ceiling framing member(s) and enclosure(s) employed.

13. Are all lighting fixtures required to be listed and labeled?

Reference: NEC 410.6

Answer: Yes, see NEC 410.6 which states All luminaires and lampholders shall be listed. This went into effect in the 2008 NEC. For the 2014 NEC all retrofit kits will also be required to be Listed.

Lighting Fixtures and Listing

14) Is it a violation to install a GFCI receptacle for the vending machine behind the vending machine indoors in a hallway of a commercial building?

Reference: NEC® 210.8 & 422.51

Answer: • No – it would not be a violation. The change in the 2011 NEC® to require GFCIs

to be readily accessible only includes those under the purview of 210.8. • 2005 NEC® section 422.51 added requirements for GFCI protection of cord-and-

plug-connected vending machines. • 2008 NEC® was revised to include a description of a vending machine, with a

FPN on the applicable product standards. • 2011 NEC® was revised by was relocating the definition to 422.2 • 2014 NEC® will include a new requirement for accessibility to devices providing

GFCI protection where such protection is specified by an Article 422 requirement.

GFCI Requirements for Vending Machines

15. Is NM-B cable allowed in any areas

of a dwelling unit that has been converted to a dental office?

Reference: 517.10(B)

Answer: Yes

SECTION 908

ELECTRICAL

908.1 Special occupancies

Where the occupancy of an existing building or part of an existing building is changed to one of the following special occupancies the electrical wiring and equipment of the building or portion thereof that contains the proposed occupancy shall comply with the applicable requirements of the International Code Council Electrical (National Electrical Code®)

ICC Building Code

1. Hazardous locations.

2. Commercial garages, repair, and storage.

3. Aircraft hangars.

4. Gasoline dispensing and service stations.

5. Bulk storage plants.

6. Spray application, dipping, and coating processes.

7. Health care facilities.

8. Places of assembly.

9. Theaters, audience areas of motion picture and television

studios, and similar locations.

10. Motion picture and television studios and similar locations

908.1 Special Occupancies

517.2 Definitions

Health Care Facilities. Buildings or portions of buildings in which medical, dental, psychiatric, nursing, obstetrical, or surgical care are provided

Patient Care Area. Any portion of a health care facility wherein patients are intended to be examined or treated.

517.10 Applicability

(A) Part II shall apply to patient care areas of all health care facilities.

(B) Not Covered. Part II shall not apply to: (1) Business offices, corridors, waiting rooms, and the like in clinics, medical and dental offices, and outpatient facilities

517.13 Grounding of Receptacles and Fixed Electrical Equipment in Patient Care Areas

Wiring in patient care areas shall comply with 517.13(A) and (B)

517.13 Grounding of Receptacles and Fixed Electrical Equipment in Patient Care Areas

(A) Wiring Methods. All branch circuits serving patient care areas

shall be provided with an effective ground-fault current path by

installation in a metal raceway system, or a cable having a metallic

armor or sheath assembly.

The metal raceway system, or metallic cable armor, or sheath

assembly shall itself qualify as an equipment grounding conductor in

accordance with 250.118.

517.13 Grounding of Receptacles and Fixed Electrical Equipment in Patient Care Areas

(B) Insulated Equipment Grounding Conductor. (1) General. The following shall be directly connected to an insulated copper equipment grounding conductor that is installed with the branch circuit conductors in the wiring methods as provided in 517.13(A).

(1) The grounding terminals of all receptacles.

(2) Metal boxes and enclosures containing receptacles.

(3) All non–current-carrying conductive surfaces

15. Is NM-B cable allowed in any areas of a dwelling unit that has been converted to a dental office?

Answer: YES

16. Are the conductors from a photovoltaic array required to have overcurrent

protection when they enter a building? What if the modules are AC modules?

Reference: 690.9 and 690.11

Answer: Requirements for overcurrent protection are independent of whether

or not the conductors enter a building. “690.9 (A) Circuits and Equipment.

Photovoltaic source circuit, photovoltaic output circuit, inverter output

circuit, and storage battery circuit conductors and equipment shall be

protected in accordance with the requirements in Article 240.” Overcurrent

protection whether for AC or DC has nothing to do with whether or not the

conductors enter the building. The question may be confusing AFCI

protection, which is not overcurrent protection. Per 690.11, DC AFCI

protection is required where photovoltaic systems are installed on or

penetrate a building

Photovoltaic/ Overcurrent Protection

17. A 200-amp circuit is increased from 3/0 copper to 500 kcmil copper to compensate for voltage drop. What size copper equipment grounding conductor would be required for this circuit?

Reference: NEC 250.122(B) increased in proportion to the increase of the ungrounded conductors

Answer:

500,000 cm = 2.98 (Ratio of increase)

167,800 cm

26,240 cm (6 AWG EGC) X 2.98 = 78,195 cm = 1 AWG EGC

Size of GEC Related to Voltage Drop

MC cable horizontally run through studs

18) Is it required to maintain 1 ¼” or use a nail plate when running MC horizontally through shallow metal studs?

Reference: NEC® 330.17 Answer: No – 330.17 (in part): 330.17 Through or Parallel to Framing Members. Type MC cable shall be

protected in accordance with 300.4(A), (C), and (D) where installed through or parallel to framing members.

• (A) refers cables & raceways routed through wood framing members

• (C) refers to NM cables and ENT routed through metal framing members

• (D) refers to cables and raceways routed parallel to framing members

19. If a rooftop unit comes with a built in GFCI receptacle on the face

of the unit that comes with the old wet location trim cover. Is it within the AHJ’s

jurisdiction to require an in-use cover and WR type receptacle?

Reference: 90.4, 90.7, 300.1(B), 406.9(B)(1), LZFE pg. 239 UL WB

Answer: Yes and No. AHJ always has the jurisdiction to accept or deny per 90.4.

406.9(B)(1) requires the WR receptacle and the bubble cover for premise

wiring receptacles. However, Listed HVAC equipment, NEC does not apply to

the construction of the RTU, this is governed by the safety standard . See

90.7 and 300.1(B). These products are Listed under (LZFE) on page 239 in

the 2012 UL White Book, evaluated to the Standard for Safety for Heating

and Cooling Equipment, UL 1995. Presently, UL 1995 does not require the a

WR receptacle or a bubble cover. Effective October 2014, Listed HVAC units

with receptacles will have to be WR have a bubble cover or pass the rain test

and the receptacle provided with a separate disconnect. This information

can be found in the UL Question Corner of the latest March April IAEI News

magazine.

HVAC RTU Receptacle

20) Is it legal to use the AC equipment grounding conductor as the grounding electrode conductor for the DC side grounding point in a solar photovoltaic system?

Reference: NEC® 690.47(C)(3)

Answer: • 690.47(C) Systems with Alternating-Current and Direct-Current Grounding Requirements.

Photovoltaic systems having dc circuits and ac circuits with no direct connection between the dc grounded conductor and ac grounded conductor shall have a dc grounding system. The dc grounding system shall be bonded to the ac grounding system by one of the methods in (1), (2), or (3).

• (3) Combined Direct-Current Grounding Electrode Conductor and Alternating-Current

Equipment Grounding Conductor. An unspliced, or irreversibly spliced, combined grounding conductor shall be run from the marked dc grounding electrode conductor connection point along with the ac circuit conductors to the grounding busbar in the associated ac equipment. This combined grounding conductor shall be the larger of the sizes specified by 250.122 or 250.166 and shall be installed in accordance with 250.64(E).

• 250.121 new for the 2011 NEC® prohibits an equipment grounding conductor from being

used as a grounding electrode conductor. However that is a general rule (90.3) modified by 690.47(C)(3).

Grounding Requirements for PV Systems

21. In a 22’ pole light, is it required to connect the auxiliary grounding electrode conductor going to the lug in the hand hole

to the equipment grounding conductors by means of a wire nut or split bolt?

Reference: 250.54 Answer: NO

250.54 Auxiliary Grounding Electrodes

One or more grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118…

250.54 Auxiliary Grounding Electrodes

…and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.53(A)(2) Exception

21. In a 22’ pole light, is it required to connect the auxiliary grounding electrode conductor going to the lug in the hand

hole to the equipment grounding conductors by means of a wire nut or split bolt?

Answer: NO

22. I have installed a 200 ampere, 120/240 volt, single phase, rain-tight, meter/main breaker panel with eight breaker spaces and

200 ampere rated, feed-thru lugs on the exterior of a dwelling unit. I have terminated 2/0 aluminum, SER cable on the feed-thru

lugs and ran 20 feet (total wire length) of this cable through a non-insulated basement ceiling and into a 125 ampere main

breaker panel located in the basement. The inspector wrote that the feeder cable has to be rated for 200 amperes. I believe that

I have installed this feeder to meet the requirements of the tap rules of Article 240.21(B)(2) and that the installation should be

approved. Who is correct?

Reference: Table 310.15(B)(16), 310.15(B)(7), Table 310.15(B)(7), Definition of “Tap” in 240.2, 240.21(B)(2)

Answer: The inspector is always right. The ampacity for 75 degree C 2/0 aluminum is 135 amperes, but Table 310.15(B)(7) would

allow 2/0 aluminum to serve a 150 ampere service/feeder if it meets the requirements of 310.15(B)(7). Note that it must

serve the entire building load, so there can be no other loads fed from the 200 ampere panel. So, it looks as if the ampacity

of the cable is adequate. But, now it needs to be protected. I tried using the 25 foot tap rule, but cannot, because the

conductors terminate in a 150 ampere CB which is greater than the ampacity of the conductor, and you can’t round up

when using the tap rules. In this case, going to a 3/0 would have increased the ampacity to 155 amperes, so termination in

a 150 ampere CB would be OK.

Service Entrance/ Feeder Tap

23. What is the minimum size copper grounding electrode conductor allowed to connect to a ground ring that is specified to be a 250 kcmil cu and the service is a 400A fed with 4-500 kcmil cu

Reference: NEC Table 250.66 and 250.66(C)

Answer: 500 kcmil X 4 = 2,000 kcmil

Table 250.66 requires a 3/0 AWG copper GEC

250.66(C) does not directly apply as the 250 kcmil Ground Ring is larger than the largest GEC required by Table 250.66,

Size of GEC to Ground Ring Electrode

FPLP installed in wet locations in PVC 24) In a power limited fire alarm system is it a code violation to

install FPLP (which is not listed for wet locations) in PVC conduit underground from building 1 to building 2?

Reference: NEC® Art 100 Definitions, 760.3(D), 760.179(D)

Answer: YES - 760.3(D) and 760.179 (in part)

760.3 Other Articles (D) Corrosive, Damp, or Wet Locations. Sections 110.11, 300.6, and 310.10(G), where installed in corrosive, damp, or wet locations.

•FPLP installed in wet locations in PVC 24) continued

760.179 Listing & Marking of PLFA Cables and Insulated Continuous Line-Type Fire Detectors. (in part) (D) Type FPLP. Type FPLP power-limited fire alarm plenum cable shall be listed as being suitable for use in ducts, plenums, and other space used for environmental air and shall also be listed as having adequate fire-resistant and low smoke–producing characteristics.

• Underground locations are wet locations

• Cables in wet locations must be a type listed for wet locations

25. How does one calculate the maximum number of multiple single station smoke alarms that can be interconnected in a building?

Reference: 110.3(B), NFPA 72, (UTGT) Pg. 378 UL WB

Answer: You don’t calculate the number of smoke alarms that can be interconnected, you look in the installation instructions provided with the Listed detectors and NFPA 72 the National Fire Alarm Code which limits them to 12.

Maximum Number of Smoke Alarms

26) Is the washer outlet branch circuit in a laundry room required to be AFCI protected? Is the entire laundry room required to be AFCI protected?

Reference: NEC® 210.12(A)

Answer: • No – 210.12(A) does not include a requirement for laundry rooms. • 210.12 (A) Dwelling Units. All 120-volt, single phase, 15- and 20-ampere branch

circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type, installed to provide protection of the branch circuit.

• 2014 NEC®: Revised to expand AFCI protection requirement to kitchens and

laundry areas and to specify AFCI protection is required for branch circuits supplying outlets and devices.

AFCI Requirements for Dwelling Units

27. If an electric water fountain uses a GFCI receptacle for protection, is it required to be readily accessible?

Reference: 422.52; 210.8 & Article 100

Answer: YES

422.52 Electric Drinking Fountains.

Electric drinking fountains shall be protected with ground-fault circuit-interrupter protection.

The GFCI protection may be an integral part of the fountain, may be provided at the receptacle for the fountain, or on the branch circuit feeding the fountain.

ARTICLE 422 Appliances IV. Construction

The ground-fault circuit-interrupter shall be installed in a readily accessible location.

210.8 Ground-Fault Circuit-Interrupter Protection for Personnel

Accessible, Readily (Readily Accessible). Capable of being reached quickly for operation, renewal, or

inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or

to resort to portable ladders, and so forth.

100. Definitions

27. If an electric water fountain uses a GFCI receptacle for protection, is it required to be readily accessible? Answer: YES

28. If we have a 125HP fire pump that is located in another room from the fire pump control (not within sight), do I need to install another disconnect for the pump if the fire pump controller disconnect is lockable? If I do install a disconnect switch, what is the rating of the switch?

Reference: 695.4(B)(1)(a) General. A single disconnecting means and associated overcurrent protective device(s) shall be permitted to be installed between the fire pump power source(s) and one of the following:

Answer: Not only is the disconnect not needed, per 695.4(B)(1), it is not allowed. The disconnect at the controller is sized to carry the locked rotor current of all the permitted motors plus the sum of any other fire pump auxiliary loads.

Fire Pump/ Switch Location

29. Where the utility company installs 1/0 aluminum service conductors instead of the 4/0 AL that are required per NEC for a 200 amp service is it compliant to install a 8 AWG GEC per 250.66

Reference: NEC Table 250.66 Note 2

Answer: The conductors installed by the utility would be either a service lateral or service drop, neither of which are covered by the NEC. The size of conductors required by the NEC would require a 4 AWG GEC unless the exception of 250.66(A) applies.

Insulating Restrictions

Bonding Low Voltage Enclosures

30) Is it required to ground or bond all metal low voltage enclosures throughout a commercial building?

Reference: NEC® 250.96(A), 250.112(I)

Answer – No 250.96 Bonding Other Enclosures. (in part)

(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non–current-carrying parts that are to serve as equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them.

Bonding Low Voltage Enclosures 30) Continued

250.112(I) Specific Equipment Fastened in Place (Fixed) or Connected by Permanent Wiring Methods (in part)

(I) Remote-Control, Signaling, and Fire Alarm Circuits. Equipment supplied by Class 1 circuits shall be grounded unless operating at less than 50 volts. Equipment supplied by Class 1 power-limited circuits, by Class 2 and Class 3 remote-control and signaling circuits, and by fire alarm circuits shall be grounded where system grounding is required by Part II or Part VIII of this article.

• Does the system require grounding?

• Are there special requirements such as for Haz Loc installations or electric signs, etc.?

• If so, the answer may change to Yes

31. Do emergency lights with individual battery back-up require a test

switch and a charging indicator light? If yes, do they have to be visible??

Reference: FTBR, Pg. 158 UL White Book, UL 924

Answer: Yes and Yes. Listed under Emergency Lighting and power

Equipment (FTBR), see pg. 158 in the 2012 UL White Book.

The Standard for Safety for Emergency Lighting and Power Equipment UL 924.

requires equipment incorporating storage batteries and battery-charging

means shall provide audible or illuminated visible indicator(s) detectable to

facility occupants without the need to adjust or remove any equipment

covers or parts they also need a test switch or provision to connect a test

switch (which can be mounted remote from the equipment, for easier

access).

Emergency Lights Battery Back-up

32) The 2-pole 50-amp GFCI breaker for a hot tub is installed in the disconnect 6 feet from the tub. It is a 240-volt 3-wire hot tub. Is a neutral required to be brought to the disconnect for the reference of the GFCI breaker? Or can the factory white neutral reference from the breaker be terminated on the equipment ground bar?

Reference: NEC® 680.44 & 110.3(B)

Answer: • 680.44: specifies the outlet(s) that supplies a self-contained spa or hot tub,

a packaged spa or hot tub equipment assembly, or a field-assembled spa or hot tub shall be protected by a ground-fault circuit interrupter.

GFCI Breaker Requirements

33. Where conduit is required for life safety & critical branch circuits, is it a violation to use factory fixture whip taps for

the 6’ termination to a 2’x4’ emergency light?

517 Part III Essential Electrical System

517.30(B) (2) Emergency Systems. The emergency system shall be limited to circuits essential to life safety and critical patient care. These are designated the life safety branch and the critical branch.

517.30(C)(3) Mechanical Protection of the Emergency System.

The wiring of the emergency systems in hospitals shall be mechanically protected. The following wiring methods shall be permitted:

(3) Listed flexible metal raceways and listed metal sheathed cable assemblies in any of the following:

a. Where used in listed prefabricated medical headwalls

b. In listed office furnishings

c. Where fished into existing walls or ceilings, not otherwise accessible and not subject to physical damage

d. Where necessary for flexible connection to equipment

33. Where conduit is required for life safety & critical branch circuits, is it a violation to use factory fixture whip taps for

the 6’ termination to a 2’x4’ emergency light?

Answer: NO

34. A 100 hp, 3-phase, 480 volt motor is fed with #2/0 AWG, Type THHN/THWN, copper conductors

protected with Type Non-400 ampere fuses and a #6 AWG copper EGC. Are the motor circuit conductors,

EGC, and fuses properly sized?

Reference: Table 430.52 (and Exception No. 1), 240.6), Table 430.250, 430.22, Table 310.15(B)(16),

250.122, and Table 240.122.

Answer: From Table 430.52 a non-time delay fuse can be sized as high as 300% of FLA, which is 124

amperes from Table 430.250. 3 X 124 = 372 amperes. Exception No. 1 allows the next standards size,

which 240.6 shows as a 400 ampere fuse, which agrees with the question. However, the fuse in

question is only a 250 volt fuse, so it would be a violation of 110.3(B) to use the 250 volt fuse on a 480

system. An NOS 400 fuse would be required for this application. 430.22 requires that the motor

circuit conductor have an ampacity of at least 1.25 X 124 = 155 amperes. Table 310.15(B)(16) shows a

2/0, 75 degree C conductor to have an ampacity of 175 amperes. Table 250.122 would indicate that a

3 AWG conductor is adequate for the EGC, so the 6 AWG conductor would also be in violation.

Sizing Motor Circuits/ Fuse, EGC, and Conductors

35. Why is a UFER connection required to be accessible?

Reference: NEC 250.68(A) Exception

Answer: The connection is not required to be accessible due to the nature of the connection inside poured concrete.

GEC Connection to Ufer GEC

Bushing on RMC nipple?

36) I installed a short rigid nipple out the back of a panel to an LB that has a 5’ length of EMT to a disconnect switch for an AC unit. It only has #10 copper wires in the conduit and the inspector wants a bushing on the inside of the panel. Is he correct?

Reference: NEC®310.4(G) and 344.46

Answer - No unless fitting or raceway does not provide smooth edge

310.4(G) Insulated Fittings. (in part) Where raceways contain 4 AWG or larger insulated circuit conductors, and these conductors enter a cabinet, a box, an enclosure, or a raceway, the conductors shall be protected by an identified fitting providing a smoothly rounded insulating surface, unless the conductors are separated from the fitting or raceway by identified insulating material that is securely fastened in place.

Bushing on RMC nipple? 36) Continued

310.4(G) Exception: Where threaded hubs or bosses that are an integral part of a cabinet, box, enclosure, or raceway provide a smoothly rounded or flared entry for conductors.

344.46 Bushings. Where a conduit enters a box, fitting, or other enclosure, a bushing shall be provided to protect the wires from abrasion unless the box, fitting, or enclosure is designed to provide such protection.

• If the nipple is listed, it is required by UL 6 to provide the smooth edge, and would meet the requirement in 344.46.

• If the nipple was manufactured in the field then it would be up to the AHJ to determine if the nipple provides a smoothly rounded edge for the conductors to pass over.

37. I have a junction box that is 1/16th of an inch thick that is painted. I drilled and tapped that box for a 10/32 screw for bonding the box. Do I need to remove the paint or will the thread contact be sufficient for making contact between the lug and the box?

Reference: 250.12

Answer: Yes, you need to remove the paint. 250.12 states Nonconductive coatings (such as paint, lacquer, and enamel) on equipment to be grounded shall be removed from threads and other contact surfaces to ensure good electrical continuity or be connected by means of fittings designed so as to make such removal unnecessary.

Grounding Lug to Painted Box

38) Are ground bushings listed for a choke on the GEC when installed in a ferrous raceway?

Reference: NEC® 250.64(E) & 250.92(B)

Answer:

• 250.64(E) …Ferrous metal enclosures that are not physically continuous from cabinets or equipment to the grounding electrode shall be made electrically continuous by bonding each end of the raceway or enclosure to the grounding electrode conductor.

• Bonding methods in compliance with 250.92(B) for installations at service equipment locations and with 250.92(B)(2) through (B)(4) for other than service equipment locations shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode.

• Grounding bushings are Listed under Grounding and Bonding Equipment, (KDER)

• These bonding connections are necessary so that the ferrous raceway does not create an inductive choke on the grounding electrode conductor. By virtue of the bonding connection, there is no choke.

Ground Bushings

39. Is it compliant to run health care facility cable through PVC in the concrete floor as long as it is not slab on grade

for dental chair receptacles?

Reference 517.13 Answer: Maybe

The metal raceway system, or metallic cable armor, or

sheath assembly shall itself qualify as an equipment

grounding conductor in accordance with 250.118.

517.13 (A) Wiring Methods

Underground cable installed under a building shall be in a raceway.

Exception No. 2: Type MC Cable listed for direct burial or concrete encasement shall be permitted under a building without

installation in a raceway in accordance with 330.10(A)(5) and in wet locations in accordance with 330.10(A)(11).

300.5(C) Underground Cables Under Buildings

330.10 Uses Permitted

(A) General Uses. Type MC cable shall be permitted as follows:

(1) For services, feeders, and branch circuits. (2) For power, lighting, control, and signal circuits. (3) Indoors or outdoors. (4) Exposed or concealed. (5) To be direct buried where identified for such use. (6) In cable tray where identified for such use. (7) In any raceway. (8) As aerial cable on a messenger.

Nonmetallic boxes shall be permitted only with open wiring on insulators, concealed knob-and-tube wiring, cabled wiring methods with entirely nonmetallic sheaths, flexible cords, and nonmetallic raceways.

Exception No. 1: Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables

314.3 Nonmetallic Boxes

330.40 Boxes and Fittings

Fittings used for connecting Type MC cable to boxes, cabinets, or other equipment shall be listed and identified for such use.

Courtesy Thomas & Betts

39. Is it compliant to run health care facility cable through PVC in the concrete floor as long as it is not slab on grade for dental chair

receptacles?

Answer: Maybe, if the MC cable can be properly terminated to a listed box or assembly at or beneath the dental chair

40. When determining the Maximum Rating or Setting of Motor Branch-Circuit Short-Circuit

and Ground-Fault Protective Device using Table 430.52, do I use the motor amperages shown

in Tables 430.247 through 430-250 for all type of motor applications or the nameplate rating

on the motor(s)? and why?

Reference: 430.6(1) Table Values. Other than for motors built for low speeds (less than 1200

RPM) or high torque, and for multi-speed motors, the values given in Table 430.247, Table

430,248, Table 430.249, and Table 430.250 shall be used to determine the ampacity of

conductors or ampere ratings of switches, branch-circuit short-circuit and ground-fault

protection, instead of the actual current rating marked on the motor nameplate.

Answer: Use the tables for all but low speed, high torque and multi-speed motors. Tables are

used because motors need to be changed out at times and the branch circuit components

need to be large enough to handle the new motor that is being installed to replace the old

motor. If motor nameplate were used and a very high efficiency motor were installed the

first time, the motor branch circuit components might not be rated high enough if a

standard motor were installed in place of the high efficiency motor.

Sizing Motor Circuits/ Use of the Tables

41. Can the concrete pillars used to support a manufactured home be used for the UFER grounding electrode?

Reference: NEC 250.52(A)

Answer: Probably not if the pillars are installed in the usual manner, that is, from concrete blocks on the earth surface.

To qualify, a pillar would need to meet the description of a grounding electrode in 250.52(A).

Support Pillars Acceptable as Ufer GEC?

MC and outlet boxes in raised floor of IT room 42) For power distribution units (PDU’s) inside a room

designated “information technology” with field installation using MC to 4plex receptacle boxes under the floor, is it required to secure and support the boxes and wiring methods as stated in 645.5(E)(2)? Or, would this installation meet the requirements in 645.5(F)?

Reference: NEC® 645.5 (E)(2) and 645.5(F) and 300.11

Answer: Possibly • If the assembly is not listed as IT Equipment or for IT Equipment the MC

cable and boxes must be secured in place in accordance with 300.11.

• 300.11 requires them to be fastened in place without using ceiling/floor support wires as the means of support.

• If the assembly is listed as IT Equipment or for IT Equipment the assembly is not required to be secured in place.

43. Since there is only one inverter that is third party listed as being arc-fault protected, should the requirements of NEC 690.11 be enforced for all inverters therefore only approving 1 type that has many restrictions? IE.. Only 3-5kws are listed?

Reference: 690.11, 90.4, (QIDC) Pg. 325 UL WB

Answer: Actually up to 11 KW are Listed for SMA Solar under the product category PHOTOVOLTAIC DC ARC-FAULT CIRCUIT PROTECTION (QIDC) located on page 325 in the 2012 UL White Book. If there aren’t sizes available for an installation under 90.4 the AHJ under special permission may permit products that complied with the previous version of the Code.

PV Inverters with AFCI Protection

44) In a small aircraft hanger where the aircraft has its’ fuel tanks in its’ wings is it allowed to have electrical outlets on the side walls by the wings for servicing the aircraft?

Reference: NEC® 513.3 & 513.4

Answer:

• Yes – see section 513.3 & 513.4

• 513.3 Classification of Locations: (A) Below Floor Level – Class I, Division 1 or Zone 1 (B) Areas Not Cut Off or Ventilated. The entire area Class I, Division 2 or Zone 2

location up to a level 18 in. above the floor. (C) Vicinity of Aircraft.

Aircraft Hangars

513.3(C) Vicinity of Aircraft: (1) Aircraft Maintenance and Storage Hangars. The area within

1.5 m (5 ft) horizontally from aircraft power plants or aircraft fuel tanks shall be classified as a Class I, Division 2 or Zone 2 location that shall extend upward from the floor to a level 1.5 m (5 ft) above the upper surface of wings and of engine enclosures.

44) In a small aircraft hanger where the aircraft has its’ fuel tanks in its’ wings is it allowed to have electrical outlets on the side walls by the wings for servicing the aircraft?

513.4 Wiring and Equipment in Class I Locations. Requires all wiring and equipment installed in or operating within Class I

locations defined in 513.3 are required to meet the applicable provisions of Article 501 or Article 505 for the division or zone in which they are used.

Attachment plugs and receptacles in Class I locations shall be identified for

Class I locations or shall be designed such that they cannot be energized while the connections are being made or broken.

Aircraft Hangars

45. In an operating room that has been identified as a “wet procedure location” can a regular receptacle

trim plate be used?

Reference: 517.19(A) Answer: YES

517.2 Definitions: Critical Care Areas

Those special care units, intensive care units, coronary care units, angiography laboratories, cardiac catheterization laboratories, delivery rooms, operating rooms, and similar areas in which patients are intended to be subjected to invasive procedures and connected to line-operated, electro-medical devices.

517.2 Definitions: Wet Procedure Locations

Those spaces within patient care areas where a procedure is performed and that are normally subject to wet conditions while patients are present.

These include standing fluids on the floor or drenching of the work area, either of which condition is intimate to the patient or staff.

517.19 Critical Care Areas

(A) Patient Bed Location Branch Circuits Emergency system receptacles shall be identified and shall

also indicate the panelboard and circuit number supplying them.

2014 NEC 517.19(C) (new)

(C) Operating Room Receptacles.

(1) Minimum Number and Supply. Each operating rooms shall be

provided with a minimum of thirty six receptacles

45. In an operating room that has been identified as a “wet procedure location” can a regular receptacle trim plate be used?

Answer: YES

46. Is it permissible to use 240.4(b) and round up to the next standard size over current device on a feeder tap? Example; Can 23 feet of 500 kcmil, Type THHN/THWN copper conductors be tapped off of a 1200 ampere feeder and terminated on a 400 amperes main breaker in a subpanel?

Reference: 240.21(B) Feeder Taps. Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (B)(5). The Provisions of 240.4(B) shall not be permitted for tap conductors.

Answer: No. Ampacity of 500 kcmil is 380 amperes, so it cannot be used to terminate into a 400 ampere main breaker for either the 10 foot tap or the 25 foot rule.

Tap Rules/ No Rounding up

47. Are dusttight “Hoffman type” junction boxes with Meyers Hubs listed for

use in a Class II Division I location approved for use in a Class II, Division I

location as a pull through only box when sized correctly even though the box

is not identified for use in a Class II location, but listed dusttight only?

Reference: 502.10(A)(4) (Class II, Div. 1) Fittings and boxes shall be provided

with threaded bosses for connection to conduit or cable terminations and

shall be dusttight. Fittings and boxes in which taps, joints, or terminal

connections are made, or that are used in Group E locations, shall be

identified for Class II locations.

Answer: A pull box without “taps, joints, or terminal connections,” is acceptable

in the Class II Division 1 area if dusttight.

Use of Dusttight J-Boxes on Class II, Div 1 Areas

Show window at a Bank? 48) Where a freestanding bank is built having about 75% full

length windows mostly for security reasons. Is it required to have the contractor install show window receptacles?

Reference: NEC® 100 (Definitions) and 210.62

Answer Maybe Show Window. Any window used or designed to be used for the display of goods

or advertising material, whether it is fully or partly enclosed or entirely open at the rear and whether or not it has a platform raised higher than the street floor level

210.62 Show Windows. At least one receptacle outlet shall be installed within 450 mm (18 in.) of the top of a show window for each 3.7 linear m (12 linear ft) or major fraction thereof of show window area measured horizontally at its maximum width

• Will they use reader boards, or other signage in the windows?

• Do they advertise using the windows?

49. Can a 30-amp water heater use a cord connector and receptacle as the disconnecting means?

Reference: 110.3(B),(KSDT) Pg. 235 UL White Book, UL 174

Answer: No, see Household Water Heaters, Storage Tank (KSDT) which states that these water heaters are intended for household use and permanent connection to the supply source in accordance with the NEC.

UL 174, permits only small capacity water heaters (5 gal. or less) to be cord and plug connected.

Cord Connected Water Heater

50) Why are sunrooms specifically listed to be AFCI protected but not an enclosed porch or patio?

Reference: NEC® 210.12(A)

Answer: • 210.12(A) Dwelling Units. All 120-volt, single phase, 15- and 20-ampere branch

circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type, installed to provide protection of the branch circuit.

• 210.52(A) General Provisions. In every kitchen, family room, dining room, living

room, parlor, library, den, sunroom, bedroom, recreation room, or similar room or area of dwelling units, receptacle outlets shall be installed in accordance with the general provisions specified in 210.52(A)(1) through (A)(3).

• IRC: Sunroom Addition: A one-story structure added to an existing dwelling with

a glazing area in excess of 40 percent of the gross area of the structure’s exterior walls and roof.

Sunroom AFCI Requirements

National Electrical Code Forum

Your Questions Answered

John Benson Electrical Engineer-Ft Collins, CO

Meet Your Distinguished Experts Moderator: Mike Forister Cheyenne, Wyoming

Don Iverson Midwest Field Rep, NEMA, CMP 1-Mason, MI

John Stacey Western Section President, CMP 6-St Louis, MO

Chuck Mello Underwriters Laboratories, CMP 5-Milwaukie, OR

Alan Manche Schneider Electric-, CMP 10, Lexington, KY

Steve Conrad Program Administrator DORA-Denver, CO

Junction Box Size

51. What is the minimum size of junction box that can be installed to enclose a power distribution block that measures 6” x 6” and has two parallel 3/0 AWG copper conductors per phase terminated on both sides of the block?

Reference: NEC 314.28(E) with 314.28(A)(2) and Table 312.6(A)

Answer: NEC 314.28(E) permits power distribution blocks in boxes over 100 cubic inches with wiring handling, routing, and termination restrictions per 312.6. Table 312.6(A) requires minimum bending space of 4 inches for the #3/0 conductors. With the 6 inch power distribution block and with conductors terminated at both sides, the minimum width of the box would be 6+4+4 = 14 inches. Also note that dimensions must meet installation instructions for the power distribution block.

• Reference; 250.104(A)(1)(2)(3)

• No, (1) states the water line must be bonded to the service equipment

enclosure, the grounded conductor at the service, the grounding

electrode conductor where of sufficient size, or to one or more

grounding electrodes used.

• #(2) and #(3) do not apply to the installation described.

• The bonding conductor is sized per 250.66 (4 AWG cu. Or 2 AWG al.)

52. Can I bond the waterline to a sub panel ground bar and not at the main panel if the incoming waterline is plastic and the house waterline is copper? If so, what size wire do I need to bond it with if I’ve fed the house with 4/0 aluminum?

Water Pipe Bonding Methods

• 550.25 states that AFCI protection is required and shall comply with 210.12. Why then do these leave the factory without the AFCI protection installed in the panels?

Answer: NO. Title 24 HUD 3280.801 Scope.

(a) Subpart I of this part and Part II of Article 550 of the National Electrical Code (NFPA No. 70–2005) cover the electrical conductors and equipment installed within or on manufactured homes and the conductors that connect manufactured homes to a supply of electricity.

AFCI Protection – A Proven Safety Device.

Question #53

Answer Continued: (b) In addition to the requirements of this part and Part II of Article 550 of the National Electrical Code (NFPA No. 70–2005), the applicable portions of other Articles of the National Electrical Code must be followed for electrical installations in manufactured homes. The use of arc-fault breakers under Articles 210.12(A) and (B), 440.65, and 550.25(A) and (B) of the National Electrical Code, NFPA No. 70–2005 is not required. However, if arc-fault breakers are provided, such use must be in accordance with the National Electrical Code, NFPA No. 70–2005. Wherever the requirements of this standard differ from the National Electrical Code, these standards apply.

AFCI Protection

Question #53

If I have a separate underground service for a fire pump entering the fire pump controller at the nearest point of entry and the controller has a disconnecting means built into it (they are all service rated by code), do I need a additional disconnecting means ahead of the controller?

Fire Pumps

Question #54

• Answer: 2011 NEC: An additional disconnect means is not required. The connection being described is considered a direct source connection per 695.4(A). See below. Article 695 permits fire pump source connections to be either direct or through a disconnecting means (695.4(B)).

• 695.4(A) Direct Connection. The supply conductors shall directly connect the power source to either a listed fire pump controller or listed combination fire pump controller and power transfer switch.

• Note: Fire pumps are typically considered three wire motor loads so be sure the fire pump controller is ordered with a neutral if installed on a grounded system. NEC 250.24(C) requires the grounded conductor be brought to the service equipment

Fire Pumps

Question #54

55. What would be the minimum size of grounded service conductor that would be required for an industrial facility with a 2000 ampere service consisting of 5 parallel runs in 5 conduits of 600 kcmil Type THWN-2 copper conductors? (there are no neutral loads on the system).

Size of Grounded Service Conductor

Answer - Based on the information in the question the minimum required size would be 1/0 copper or 3/0 aluminum in each raceway. Even though there are no phase to neutral loads from the service, 250.24(C) would require the installation of grounded service conductors (neutrals) to the service equipment. Again since there are no neutral loads, then calculation of neutral conductor size from 220.61 would not be required. Section 250.24(C) does specify a minimum sizing in accordance with (C)(1) or (C)(2) for either single raceway or multiple raceways respectfully. With multiple raceways 250.24(C)(2) would require the size be based on the size of the ungrounded conductors in each raceway using Table 250.66 and not smaller than 1/0 AWG.

Size of Grounded Service Conductor

56. Is it permissible to utilize Table 310.15(B)(7) and install two parallel runs of 4/0 aluminum SER cable for a 400 ampere main power feeder for a single family dwelling?

Reference: NEC 310.15(B)(7)

Answer: No, this section requires that the conductors be the main power feeder (not feeders)

• A 400 ampere service requires 400 kcmil copper or 600 kcmil

aluminum as provided in the Table 310.15(B)(7).

Main Power Feeder / Paralleled?

Disconnect Access

57. An RTU is placed on a metal frame for weight dissipation & built up to where the controller and the breaker (disconnect) is now 8’ AFF. Is it required to install a working platform 30” x 36” or is a ladder to access and service the unit NEC compliant using the exception to 404.8 exception (2) & 240.24(a)(4)

Reference: NEC 404.1 with 404.8, Exception No. 2

Answer: The circuit breaker disconnect location for the RTU is governed by NEC Article 404 per NEC 404.1. With the disconnect mounted at the elevated RTU equipment, access by portable means (ladder) is allowed by NEC 404.8, Exception No. 2 in lieu of a service platform.

58. I have two Islands in my house, one is for the kitchen and one is for my wet

bar in another room. They both have a receptacle within 6’ of the sink

installed on the back side of the island. The inspector is requiring that the one

for the wet bar be GFCI protected and not requiring that for the kitchen. Is

that a proper interpretation of the 2011 NEC?

Reference: NEC 210.8 (A)(6)(7)

Answer: It depends on the placement of the island outlet in the

kitchen area. If the outlet is located low and is NOT intended to serve the

countertop surfaces the inspectors interpretation is correct per 210.8(A)(6).

The island outlet for the other wet bar must be GFCI protected per

210.8(A)(7).

GFCI PROTECTION

• Can PVC conduit be installed under the floor of a Commercial Garage (NEC 511) and if so with what restrictions?

Commercial Garages

Question #59

Answer: Yes.

In 511.4 (A) Wiring and Equipment in Class I Locations shall conform to the

applicable provisions Art 501.

501.10 Wiring Methods (A) (1) (a) Exception; Type PVC conduit and type RTRC

conduit shall be permitted where encased in a concrete envelope a minimum

of (2 in.) thick and provided with not less than (24 in.) of cover measured from

the top of the conduit to grade. Where this exception is used, threaded rigid

metal conduit or threaded steel intermediate metal conduit shall be used for

the last (2ft) of the underground run to emergence or to the point of

connection to the aboveground raceways, and a equipment grounding

conductor shall be included to provided electrical continuity of the raceway

system and for grounding of non-current-carrying metal parts

Commercial Garage

Question #59

Can a service be located beneath the down spout or over flow scupper of a building?

Answer: No. See NEC 230.54(G).

(G) Arranged That Water Will Not Enter Service Raceway or Equipment. Service-entrance and overhead service conductors shall be arranged so that water will not enter service raceway or equipment.

Question #60

61. How is it NEC compliant to have a #8 Supply side bonding jumper and 4-#3cu on the line side of a 100a service disconnect (which may be one of 6 justifying the large transformer)being fed from a 500kva 13.2 KV to a 208v utility transformer? Would any of these conductors hold up in a ground fault or short circuit situation? Is this an area that requires a code change?

Conductors Withstand Ratings

Answer - Assuming a transformer impedance of 5 percent and an unlimited supply the available 3 phase short circuit current at the transformer is 27,750 Amps. This would be reduced to some lower value at the service equipment based on the length and size of the service conductors. For estimating purposes, the ground fault current imposed on the 8 AWG copper supply side bonding jumper would be about 33% of the 3-phase value or about 9000 Amps. The current withstand rating of 8 AWG copper for 9000 Amps is 2 to 3 cycles and fuses or circuit breakers rated 100 Amps would clear this level of fault in 1 to 2 cycles. The 3 AWG copper conductors would withstand the 27,000 Amps for 2 to 3 cycles so the same would apply to these conductors under full bolted fault short circuit conditions. This is already covered by the requirements in 110.9 and 110.10.

Conductors Withstand Ratings

62. What is the maximum allowable ampacity for (6) 3 AWG THHN copper

current-carrying conductors installed in EMT in an ambient temperature of

110 F. and terminated in 60 C. lugs?

Reference: NEC 110,14(C), 310.16(B)(16) 310.15(B)(2)(a) and (3)(a) • 110.14(C) states that we can use the rating of the conductor (THHN is 90 degree)

ampacity for adjustment and correction factors however the final ampacity cannot exceed the lowest temperature rating of any connected termination. Since the terminations are 60 degree the ampacity is limited to 85 amperes in Table 310.15(B)(16) in the 60 degree column.

• 310.15(B)(16) allows 115 amps for a 3 AWG THHN in the 90 degree column.

310.15(3)(a) requires an 80% ampacity adjustment for 6 current carrying conductors. 115 x .80 = 92 amperes.

310.15(B)(2)(a) requires a correction factor of .87 for 110 degree ambient temperature in the 90 degree column. .87 x 92 = 80 as the maximum allowable ampacity.

• 80 amps are less than 85 amps therefore meeting the 60 degree requirement of 110.14(C)

Ampacity/Adjustment/Correction/Termination

Farm Demand Load

63. What is the total demand load in kVA for a farm with a 30 kVA dwelling, a 10 kVA barn and a 3 kVA storage shed?

Reference: NEC 220.103 with Table 220.103…

Answer: For farm load calculation on a common electrical service with a dwelling, Table 220.103 may be used for the farm loads that are added to the 30 KVA dwelling demand load. The resulting calculation will be :

30 KVA + (10 KVA x 1.00) + (3.0 x 0.75) =

30+10+2.25 = 42.25 KVA

• Smoke detector requirements are not in the NEC. Placement, power supply, and interconnection requirements are in the building code.

64) Do wireless interlocked smoke detectors meet the building code requirement for interlocking smoke detectors in dwelling units, or must they be hard wired?

•Smoke Detector Requirements

SECTION R314 SMOKE ALARMS R314.1 Smoke detection and notification. All smoke alarms shall be listed in accordance with UL 217 and installed in accordance with the provisions of this code and the household fire warning equipment provisions of NFPA 72.

R314.2 Smoke detection systems. Household fire alarm systems installed in accordance with NFPA 72 that include smoke alarms, or a combination of smoke detector and audible notification device installed as required by this section for smoke alarms, shall be permitted. The household fire alarm system shall provide the same level of smoke detection and alarm as required by this section for smoke alarms. Where a household fire warning system is installed using a combination of smoke detector and audible notification device(s), it shall become a permanent fixture of the occupancy and owned by the homeowner. The system shall be monitored by an approved supervising station and be maintained in accordance with NFPA 72.

•Smoke Detector Requirements

Exception: Where smoke alarms are provided meeting the requirements of Section R314.4.

R314.3 Location. Smoke alarms shall be installed in the following locations: 1. In each sleeping room.2. Outside each separate sleeping area in the immediate vicinity of the bedrooms.3. On each additional story of the dwelling, including basements and habitable attics but not including crawl spaces and uninhabitable attics. Indwellings or dwelling units with split levels and without an intervening door between the adjacent levels, a smoke alarm installed on the upper level shall suffice for the adjacent lower level provided that the lower level is less than one full story below the upper level. When more than one smoke alarm is required to be installed within an individual dwelling unit the alarm devices shall be interconnected in such a manner that the actuation of one alarm will activate all of the alarms in the individual unit.

•Smoke Detector Requirements

R314.3.1 Alterations, repairs and additions. When alterations, repairs or additions requiring a permit occur, or when one or more sleeping rooms are added or created in existing dwellings, the individual dwelling unit shall be equipped with smoke alarms located as required for newdwellings. Exceptions:

1. Work involving the exterior surfaces of dwellings, such as the replacement of roofing or siding, or the addition or replacement of windows or doors, or the addition of a porch or deck, are exempt from the requirements of this section.

2. Installation, alteration or repairs of plumbing or mechanical systems are exempt from the requirements of this section.

•Smoke Detector Requirements

R314.4 Power source. Smoke alarms shall receive their primary power from the building wiring when such wiring is served from a commercial source, and when primary power is interrupted, shall receive power from a battery. Wiring shall be permanent and without a disconnecting switch other than those required for overcurrent protection. Smoke alarms shall be interconnected.

Exceptions: 1. Smoke alarms shall be permitted to be battery operated when installed in buildings without commercial power.

2. Interconnection and hard-wiring of smoke alarms in existing areas shall not be required where the alterations or repairs do not result in the removal of interior wall or ceiling finishes exposing the structure, unless there is an attic, crawl space or basement available which could provide access for hard wiring and interconnection without the removal of interior finishes.

•Smoke Detector Requirements

An old interior service panel is used as a junction box. The branch circuits are extended to a new exterior service panel. Are the branch circuits identified in NEC 210.12(A) required to be arc-fault protected?

AFCI Protection

Question #65

Answer: Yes

210.12 (B) Branch Circuit Extensions or Modifications – Dwelling Units.

In any areas specified in 210.12(A), where branch-circuit wiring is modified, replaced, or extended, the branch circuit shall be protected by one of the following:

(1) A listed combination-type AFCI located at the origin of the branch circuit.

(2) A listed outlet branch-circuit type AFCI located at the first receptacle outlet of the existing branch circuit.

AFCI Protection

Question #65

Is it a violation to install a bollard for protection of a panel which violates the working clearances while the bollard is in place but where the nuts can be removed with a simple tool to work on the panel and have the required clearances while you are servicing the panel?

Question #66

Answer: The AHJ will have to decide if the bollard and steps to remove it, allow access to the

working space. NEC 110.26(E)(2) recognizes that such protection is required for outdoor

equipment.

NEC 110.26(E)(2) Outdoor. Outdoor electrical equipment shall be installed in suitable enclosures

and shall be protected from accidental contact by unauthorized personnel, or by vehicular traffic,

or by accidental spillage or leakage from piping systems. The working clearance space shall include

the zone described in 110.26(A). No architectural appurtenance or other equipment shall be

located in this zone.

110.26 Spaces About Electrical Equipment. Access and working space shall be provided and

maintained about all

electrical equipment to permit ready and safe operation and maintenance of such equipment.

Question #66

67. A solar photovoltaic system is installed on a detached garage which has a 30A sub-panel and 3-wire feeder so the grounded conductor is bonded to the grounding electrode system (ground rod) at the garage. The PV system is larger than the conductors can carry for a grid-tie system so the PV grid-tie conductors were run back to the main structure’s main panel. The PV inverter is grounded to the grounding electrode system of the detached garage. Since the garage has only a 3-wire system the grounded conductor was isolated to avoid a parallel path and the equipment ground with the PV grid-tie conductors was upsized to accommodate the two systems. Is this legal?

•Garage PV System

Answer - Maybe. With the feeder from the inverter back to the main building and service having an equipment grounding conductor the exception in 250.32(A) is no longer valid. The connection of the inverter grounding electrode conductor to the garage grounding electrode would be required by 250.58. Therefore the neutral in the garage panel would have to be isolated from the enclosure and the grounding electrode conductor. The only way the single equipment grounding conductor can serve both the inverter feeder and the garage feeder is if it was installed in the same raceway or trench using 250.122(C). If the feeders are in separate raceways then the neutral would have to be isolated and an equipment grounding conductor from the service panel to the garage panel would have to be installed per 250.32(A).

•Garage PV System

68. Can car lifts in a commercial garage be wired with cords?

Reference: NEC 511.4 501.140

Answer: Not unless there is a reason for flexibility or portability

Cords in Class 1 Locations

Luminaire Construction

69. Is a sconce with an open top considered guarded?

Reference: NEC 100 – Guarded

Answer: No, the open-top sconce would not be considered “guarded”. While the specific application is not indicated, the definition of “guarded” in Article 100 requires items to be “Covered, shielded … or otherwise protected … to remove the likelihood of approach or contact by persons or objects to a point of danger.” The open top on the sconce would not meet that requirement of protection.

• Carbon monoxide detector requirements are not in the NEC. Placement, power supply, and interconnection requirements are in the building code.

70) In Colorado, where are carbon monoxide detectors required in a dwelling unit and must they be 120-volt with battery back-up. Also, are they required to be interlocked with other interlocked smoke detectors in a dwelling unit?

•Carbon monoxide Detector Requirements

SECTION R315 CARBON MONOXIDE ALARMS

R315.1 Carbon monoxide alarms. For new construction, an approved carbon monoxide alarm shall be installed outside of each separate sleeping area in the immediate vicinity of the bedrooms in dwelling units within which fuel-fired appliances are installed and in dwelling units that have attached garages.

R315.2 Where required in existing dwellings. Where work requiring a permit occurs in existing dwellings that have attached garages or in existing dwellings within which fuel-fired appliances exist, carbon monoxide alarms shall be provided in accordance with Section R315.1.

•Carbon monoxide Detector Requirements

R315.3 Alarm requirements. Single station carbon monoxide alarms shall be

listed as complying with UL 2034 and shall be installed in accordance with this code and the manufacturer's installation instructions.

•Carbon monoxide Detector Requirements

• What is the minimum distance a smoke detector may be installed from the door of a bathroom containing a shower in a dwelling unit?

Smoke Alarms

Question #71

Answer: NEMA Standard SB 11 – 2011 provides general guidance.

“In damp or excessively humid areas, or next to bathrooms with showers. Tiny droplets can accumulate inside the sensing chamber and make the detector overly sensitive. A tremendous amount of humid air is produced during a hot shower. The moisture in this humid air can enter the sensing chamber as water vapor, then cool and condense into droplets that can cause a nuisance alarm”.

NFPA 72-2010 and 2013 prohibits a smoke alarm or detector from being installed within 36 inches from a door leading to a bathroom containing a shower or tub.

Smoke Alarms

Question #71

Are branch circuit breakers marked “SWD” and rated for 480 volts suitable for switching fluorescent lighting loads?

Answer: Yes, see NEC 240.83(D).

(D) Used as Switches. Circuit breakers used as switches in 120-volt and 277-volt fluorescent lighting circuits shall be listed and shall be marked SWD or HID. Circuit breakers used as switches in high-intensity discharge lighting circuits shall be listed and shall be marked as HID.

UL Whitebook - CIRCUIT BREAKERS, MOLDED CASE AND CIRCUIT-BREAKER ENCLOSURES (DIVQ) - Circuit breakers marked "SWD" and rated 347 V or less are suitable for switching fluorescent lighting loads on a regular basis at their rated voltage.

Circuit Breakers

Question #72

73. Manufactures of MRI machines have been adamant about there not being any metallic pathways out of the MRI room that could cause interference with the imaging. They spec an isolation coupling in the conduit of the branch circuits into the room. How are inspectors supposed to deal with this issue in regards to 517.13?

•Installation of MRI Equipment

Answer - The only circuits that should be going into the shielded MRI room are those directly related to the MRI equipment. Generally all the MRI circuits go through a special isolation panel in the wall of the special room to shield any outside coupling that could create interference to the magnetic imaging equipment as well as any of the magnetic energy to leave the room. Lighting circuits in the ceiling should be higher than where these would fall under 517.13. If the circuits are those related to the MRI equipment assembly directly, that equipment is covered under its listing and these are not building construction circuits that would be subject to 517.13 just as internal wiring in other medical equipment in a patient care area are not subject to this provision. That listing includes specific provisions for assurance of equipment grounding to the single point grounding reference to assure proper operation of the MRI equipment.

•Installation of MRI Equipment

74. A low volt panel installed outside has a receptacle inside; does this receptacle need to be WR

Reference: 406.9(B)(1)

Answer: Yes, 15- and 20-ampere, 125- and 250-volt receptacles installed in a wet location shall have an enclosure that is weatherproof whether or not the attachment plug cap is inserted. All 15- and 20-ampere, 125- and 250-volt nonlocking-type receptacles shall be listed weather-resistant type.

Wet Location / Weather-Resistant Receptacle?

Range Demand Load

75. What is the demand load for (20) 8 kW ranges installed in a multi-family dwelling?

Reference: NEC 220.55 with Table 250.55.

Answer:

Use of Column C in Table 220.55 is to be utilized for determination of loads. Note 3 permits exception primarily for loads on multiple cooking units within dwelling units. The demand load for 20 ranges rated at 8 KW is 35 KW as indicated in Column C.

Article 547.10 (A)(B)

As there are electrical devices and concrete floors in the livestock containment area equipotential plane bonding is required. Minimum 8 AWG SOLID conductor required.

76) Are the stock holding pens (with concrete floors) of a slaughter house facility required to have the equipotential plane bonded? There are stock tank heaters in the pens and chutes. The rails and posts are steel.

•Equipotential bonding in livestock containment areas.

Answer: 300.3(C) (1) Conductors of Different Systems.

(1) 600 Volts, Nominal, or less. Conductors of ac and dc circuits, rated 600 volts, nominal or less shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

Informational Note #1: See 725.136(A) for class 2 and Class 3 circuits conductors.

Barriers

Question #77

Answer Continued:

Art. 725.136(A) Separation from Electric Light, Power, Class 1 ect.

(A) General: Cables and conductors of Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, raceway, or similar fitting with conductors of electric light, power, Class 1, non-powered broadband communications circuits unless permitted by 725.136(B) through (I).

Barriers

Question #77

Answer continued:

Art. 725.136(B) Separated by Barriers.

Class 2 and Class 3 circuits shall be permitted to be installed together with the conductors of electric light, power, Class 1, non-power-limited fire alarm and medium power network-powered broadband communications circuits where they are separated by a barrier.

Barriers

Question #77

690.14 states that the ac disconnect is not required to be suitable for service equipment. Would the AC disconnect for a line side tap be required to be suitable for service equipment?

Answer: No. SUSE is not required.

If this is a utility interactive application the requirements for the point of connection are found in NEC 690.64. In the 2011 NEC, these requirements were appropriately moved to Article 705 such that NEC 690.64 simply sends you to NEC 705.12.

Question #78

Answer Continued:

690.64 Point of Connection. Point of connection shall be in accordance with 705.12.

705.12(A) Supply Side. An electric power production source shall be permitted to be connected to the supply side of the service disconnecting means as permitted in 230.82(6). The sum of the ratings of all overcurrent devices connected to power production sources shall not exceed the rating of the service.

Also see 705.20,21.22 for the disconnect requirements – SUSE is not a requirement.

Question #78

79. We have a facility that owns the 13k step down to 208v transformer that is normally owned by the utility. The transformer is located in the basement of the building in a retirement center. With fault currents over 30k, Is it legal to use the 25’ tap rule per 240.21(C)( 6) and run EMT over head to the 208v MDP or should these secondary conductors be treated as service conductors and installed to be outside the building by a permitted method?

•Transformer Feeder Installation

Answer - The transformer as described as owned by the facility would mean this is a separately derived system and that there is a service to the facility at 13KV with all related service equipment. The wiring from the transformer to the 208 Volt MDP is a feeder and the various feeder tap rules in 240.21(C) would be applicable. These conductors would have short circuit and high level ground-fault protecting provided by the primary protections device. The overload protection is provided by the secondary overcurrent device(s). Being in the basement, I am assuming this is not a vault that would be considered outside the building. So, with these assumptions the transformer secondary conductor rules for 10 foot, 25 foot etc. distances would could be applied depending on meeting the specific requirements for each of the allowed installations. This feeder could be installed in EMT from the basement to the MDP following the proper wiring methods from Chapter 3.

•Transformer Feeder Installation

80. What is the ampacity of (8) 6 AWG THHN copper current-carrying

conductors installed in EMT that have a total length of 75 feet, but of

which 8 feet pass through a boiler room with an ambient temperature of

120 F.?

Reference: NEC 310.15(A)(2) 310.(B)(16) 310.15(B)(2)(a) and (3)(a), 110.14(C)

Answer: We can start the calculation using the rating of the conductor according to 110,14.

310.15(B)(16) allows 75 amps for a # 6 THHN in the 90 degree column. 310.15(B)(3)(a) requires an 80% adjustment factor for 8 current-carrying conductors. 80% of 75 = 60 amps.

• 310,15(A)(2) States; Where more than one ampacity applies for a given circuit length, the lowest value shall be used. Because 10 ft. or 10% of the circuit runs through 120 degree boiler room a correction factor of 82% is required from 310.15(B)(2)(a)

• 60 x .82 = 49 amperes allowed. This does not exceed the 60 degree ampacity of 55 amperes meeting the requirements of 110.14(C).

Selection of Ampacity

Water Heater Circuit

81. What is the minimum size branch circuit allowed for a 4500 watt, 240-volt, 40 gallon water heater?

Reference: NEC 422.13, 210.19(A), and 240.4(D)(7)

Answer: Under NEC 422.13, storage type electric water heaters are to be considered continuous loads with a resulting demand factor of 1.25 for sizing branch circuits per 210.19(A). Using the unit element size of 4,500 watts (volt-amperes) at 240 volt, 1-phase, the calculated demand load is:

(4,500 x 1.25) / 240 = 5,625 / 240 = 23.4; rounded to 23 amperes

Using NEC 240.4(D)(7), the #10 AWG minimum conductor size would be selected with overcurrent protection at 30 amperes.

Article 547.1

The provisions of this article shall apply to the following buildings or that part of a building or adjacent areas of similar or like nature as specified in 547.1(A) or (B).

There are may be some areas of a barn where NM-B is acceptable for use. Where NM-B is installed the requirements of Article 334 must be used.

82) Is NM-B cable allowed to be used in any area of a barn?

•Use of NM-B cables in barns.

• Can a field installed receptacles and wiring methods be considered “listed for information technology equipment” per 645.5G (B) to not have to secure and support under the raised floor? What would be an example of where you have to secure & where you do not have to secure receptacles and wiring methods from a PDU under a floor?

Information Technology Equipment

Question #83

Answer: NO.

645.5(E) Branch-circuit conductors installed under the raised floor of an ITE room using any of the wiring methods listed in 645.5(E)(2) are required to conform to the specific article for the wiring method used. In addition, Article 300 applies, except where modified by Article 645. For example, 300.11 requires raceways, cables, and boxes to be securely fastened in place, even though they are installed below a raised floor.

645.5(F) Securing in Place. Power cables; communications cables; connecting cables; interconnecting cables; and associated boxes, connectors, plugs, and receptacles that are listed as part of, or for, information technology equipment shall not be required to be secured in place.

Information Technology Equipment

Question #83

For a 120v phase to phase isolated power system supplying receptacles in a hospital operating room. Is it required to install bonding bushings or bonding locknuts on the EMT entries to the 4 square boxes or is a standard locknut sufficient?

Answer: Yes, bonding bushing or bonding locknuts are required.

NEC Article 358 permits EMT to be used as an equipment grounding conductor when installed as a system and appropriate fittings are used. Article 517.13(A)/(B) set the requirements for using a metal raceway system which qualifies as an equipment grounding conductor and an insulated equipment grounding conductor to the receptacle/box.

Question #84

Answered Continued:

517.19(D) Equipment Grounding and Bonding. Where a grounded electrical distribution system is used and metal feeder raceway or Type MC or MI cable that qualifies as an equipment grounding conductor in accordance with 250.118 is installed, grounding of enclosures and equipment, such as panelboards and switchboards, shall be ensured by one of the following bonding means at each termination or junction point of the metal raceway or Type MC or MI cable:

(1) A grounding bushing and a continuous copper bonding jumper, sized in accordance with 250.122, with the bonding jumper connected to the junction enclosure or

Question #84

85. Is it NEC compliant per 110.3 to reduce the fault current by using let through current “up over down method” to protect a standard breaker panel? Is this an approved method per UL ?

•Fault Current Limiting

Answer - No. The short circuit current available at the line terminals cannot exceed the Short Circuit Current Rating of the panel. Where the quick calculation shows a possible Short Circuit Current higher than the rating, then a more detailed short circuit study or calculation needs to be done to include all wire impedances and the true available current at the supply transformer. If the fault current calculated still exceeds the rating of the panel, then either the panel will need to be replaced with one with suitable ratings or some other means, such as inserting an impedance, to reduce the flow through fault current. A current limiting fuse using the up-over-down method is not an acceptable alternative.

•Fault Current Limiting

86. How many #14 wires can I splice in a ¾” LB that is labeled with 6.5 cubic inches?

Reference: NEC 314.16(C)(2) Conduit Bodies With Splices, Taps, or Devices. 314.14(B)

Answer: Only those conduit bodies that are durably and legibly marked by the manufacturer with their volume shall be permitted to contain splices, taps, or devices. The maximum number of conductors shall be calculated in accordance with Table 314.16(B).

Table 314.16(B), shows a 14 AWG as being 2.00 cubic in. The LB is 6.5 cubic inches divided by 2.00 = 3 # 14 AWG allowed, 2 that are spliced and one passing through.

Splices in LB?

Office Demand Load

87. What is the lighting load in VA for a 10,000 sq. ft. office building, including general purpose receptacles, where the number of general purpose receptacles is unknown?

Reference: NEC 220.12, Table 220.12, and 220.14(K)

Answer: The minimum General Lighting Load for an office facility is designated in Table 220.12 as 3.5 volt-amperes (VA) per square foot (VA/SF). In addition, the general receptacle load where not available from 240(I) is designated as 1.0 VA/SF in 240.14(K). The calculation for combined general lighting and receptacle loads is:

10,000 x (3.5 + 1.0) = 10,000 x 4.5 = 45,000 VA

The AHJ always has the last say. That said there are a few areas in the code where physical protect is required such as Article 334.15 (B), (C).

88) Does the code specify protection from damage requirements or does the authority having jurisdiction make his own requirements [ as for NEC 110.26 [E]

•Protection from physical damage.

What kind of devices are allowed in a conduit body (referred to in 314.16(C)(2)?

Answer: There is not a conduit body made with a mounting yoke inside it. When 314.16(C)(2) mentions devices, they refer to all electrical devices. As you recall an electrical device is a device that either produces, consumes, or directs (receptacles) electricity. Some would even say a wire nut is a device.

Conduit Bodies

Question #89

Is it required to install a disconnecting means on each light pole since it is defined as a structure by the code making panel?

Answer: No, see NEC 225.32 Exception No. 3

225.32 Exception No. 3: For towers or poles used as lighting standards, the disconnecting means shall be permitted to be located elsewhere on the premises.

Question #90

91. Since rebar can simply be tie wired together and this is approved for the UFER. Can a CU conductor simply be tie wired to the rebar?

•Rebar Connections

Answer - No. 250.70 requires the connection of the grounding electrode conductor to the grounding electrode using exothermic welding or a suitably listed lugs, listed pressure connectors, listed clamps, or other listed means. For a connection device to be embedded in concrete it must also be listed and identified for direct burial and/or concrete encasement. Listed devices suitable for connection of grounding electrode conductors can be found under UL Category Code KDER on page 217 of the 2012 UL White Book. Tie wires are not a listed device nor specifically allowed by 250.70.

•Rebar Connections

92. On a “corner grounded delta” service, is the grounded leg required to be in the “A”, “B” or “C” phase location?

Reference: Schneider-Electric - Definitions

Answer: Corner-Grounded Delta System A system in which the transformer secondary is delta-connected with one

• corner of the delta solidly grounded. Corner-grounded delta

systems are also referred to as grounded B phase systems, grounded phase services, and end-grounded delta systems

Corner Grounded Delta / Grounded Phase?

Ground Ring Electrode

93. What is the minimum size copper grounding electrode conductor allowed to connect to a ground ring?

Reference: NEC 250.52(A)(4) and 250.66(C)

Answer: The minimum size of a ground ring encircling a building or structure shall be #2 AWG per NEC 250.52(A)(4). The minimum size for the bare copper grounding electrode conductor is established in NEC 250.66 as the values shown in Table 250.66, except as permitted in paragraphs 250.(A), (B), and (C). The grounding electrode conductor under 250.66(C) is allowed to be the same size of the conductor for the ground ring or thus #2 AWG, (unless a larger ground ring is installed).

Article 210.52(A)(2)(1)

Yes an outlet is required on the wall space.

Any space 2 feet or more in width and unbroken along the floor line by doorways and similar openings, fireplaces, and fixed cabinets.

94) Is a receptacle on 24” wall located behind the swing of a door required?

•Outlet spacing/wall spaces.

What length of a “C” Conduit body is required for #4 wire pulled in a 2” conduit?

Answer: 314.28 Pull and Junction Boxes and Conduit Bodies.

Boxes and conduit bodies used as pull or junction boxes shall comply with 314.28(A) through

(E).

• (A) Minimum Size. For raceways containing conductors of 4 AWG or larger that are

required to be insulated, and for cables containing conductors of 4 AWG or larger, the

minimum dimensions of pull or junction boxes installed in a raceway or cable run shall

comply with (A)(1) through (A)(3). Where an enclosure dimension is to be calculated based

on the diameter of entering raceways, the diameter shall be the metric designator (trade

size) expressed in the units of measurement employed.

• (1) Straight Pulls. In straight pulls, the length of the box or conduit body shall not be less

than eight times the metric designator (trade size) of the largest raceway.

Conduit Bodies

Question #95

I have a 200A service on a residence fed with 4/0 aluminum and a 100A sub panel. What size

SER cable do I need to run to the sub panel?

The requirements for using SE type cable for feeder and branch circuit wiring are found in

NEC Article 338. In particular to this question, NEC 338.10(B)(4)(a) covers indoor

installations of this cable and includes requirements for cases where the cable is installed in

thermal insulation. See the second paragraph from this section below:

Where installed in thermal insulation, the ampacity shall be in accordance with the 60°C

(140°F) conductor temperature rating. The maximum conductor temperature rating shall be

permitted to be used for ampacity adjustment and correction purposes, if the final derated

ampacity does not exceed that for a 60°C (140°F) rated conductor.

Question #96

Answered Continued: Since this installation does not qualify as a main power

feeder per NEC 310.15(B)(7), use of the table 310.15(B)(7) is not permitted and all

of the requirements of NEC 310.15 will apply in sizing the SER cable for this

installation.

Case 1: SER installed in thermal insulation, 40 C ambient. From Table

310.15(B)(16), using 60 C column, a #1 Cu or 1/0 Al size would be the minimum

size required but we must check for any adjustment or correction factors.

Checking for ambient adjustment, Table 310.15(B)(2)(a) requires a 0.91 adjustment

for 40 C ambient. Since SER cable has a temperature rating of 90 C we can use that

column from table 310.15(B)(16) so 145 A X 0.91 = 132A Cu and 135 x 0.91 = 123 A

Al.

#1 CU or 1/0 AL is required for this feeder.

Question #96

Answered Continued:

Case 2: SER NOT installed in thermal insulation, 40 C ambient. SER cable is listed as an assembly for 75 C so from Table 310.15(B)(16), a #3 Cu or #1 Al size would be the minimum size required but we must check for any adjustment or correction factors. For the adjustment and correction factors, the temperature rating of the conductors can be used, 90C.

Checking for ambient adjustment, Table 310.15(B)(2)(a) requires a 0.91 adjustment for 40 C ambient. Using the 90 C column from table 310.15(B)(16) so # 3 Cu - 115 A X 0.91 = 105A and #1 Al - 115 x 0.91 = 105 A.

#3 CU or #1 AL is required for this feeder.

Question #96

97. We have a precast building that has multiple areas, separated by the precast, containing a steel framework of beams and bar joists. The building has a 2/0 counterpoise ground system surrounding it in a ring with multiple ground rods. The lightning protection system is bonded many times to this ground, as well as the main service grounding electrode system. Building steel in each of these separate areas is also bonded to the counterpoise ground. Can the building steel be considered a grounding electrode and be used to bond the separately derived system transformers without having to run all the way back to the main service?

•Structural Steel Grounding Electrode

Answer - The building steel would be considered a grounding electrode conductor or common grounding electrode conductor per 250.68(C). Since the building steel is bonded to the overall grounding electrode system, then it would qualify and be suitable for use to ground the separately derived systems.

•Structural Steel Grounding Electrode

• 98. When the sheathing is removed from NM cable, can you treat the individual conductors as THWN or is it still NM cable?

Reference: NEC 334.80 Ampacity

Answer: It’s still NM cable; the conductors are unmarked and would be rated for 60 degree..

• The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15.

• The allowable ampacity shall not exceed that of a 60°C (140°F) rated conductor. The 90°C (194°F) rating shall be permitted to be used for ampacity adjustment and correction calculations, provided the final derated ampacity does not exceed that of a 60°C (140°F) rated conductor

NM Cable / 60 or 90 degree?

Fault Current Rating

99. On an existing commercial building a portion of the tenant space is being remodeled. During a rough electrical inspection, the service is looked at and the breakers do not have a high enough AIC rating for the available fault current. Can the inspector require the service or any of the panels being used

Reference: NEC 90.4, 110.10, 110.22, and 110.24

Answer: Under the provisions of NEC 110.10, 110.22, and 110.24, the design and application of individual system components is to be provided as needed to withstand the affects of short circuit current under fault conditions. Where an existing installation is found deficient or improperly installed, the Authority Having Jurisdiction (AHJ) has the responsibility of enforcement and determination of approval of equipment and materials, as defined in NEC 90.4. In this case, the extent and depth of such action that is required is at the discretion of the AHJ.

• Carbon monoxide detector requirements are not in the NEC. Placement, power supply, and interconnection requirements are in the building code.

100) In Colorado, where are carbon monoxide detectors required in a dwelling unit and must they be 120-volt with battery back-up. Also, are they required to be interlocked with other interlocked smoke detectors in a dwelling unit?

•Carbon monoxide Detector Requirements