MECKLENBURG COUNTY
Land Use & Environmental Services Agency
Code Enforcement
5/9/12 ELECTRICAL CONSISTENCY MEETING
1. I am building a new electrical service on a house with lightning protection already
installed. Adjacent to the electrical meter, there are two ground rods, six feet apart for
the lightning protection. My I utilized these rods to ground my service?
No, See 250.60 Use of Air Terminals.
Air terminal conductors and driven pipes, rods, or plate electrodes used for grounding air
terminals shall not be used in lieu of the grounding electrodes required by 250.50 for
grounding wiring systems and equipment. This provision shall not prohibit the required
bonding together of grounding electrodes of different systems.
2. I recently installed a new service panel and had to relocate it five feet from its
original location. The old panel had a dryer circuit run with 8-2 w/ground
aluminum Type SE cable. I extended the circuit using 6-2 w/ground Type NM-B
copper cable. The inspector said I have to continue the run with Type SE cable
or use a 4-wire Type NM-B cable so I get an insulated neutral. He said Type SE
cable is the only cable permitted without an insulated neutral. I know new
circuits require insulated neutrals and that there are requirements to maintain
the use of 3-wire with bare neutral but never heard of this nor interpreted it in
this fashion. Can you explain this?
250.140 Frames of Ranges and Clothes Dryers.
Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes
dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be
connected to the equipment grounding conductor in the manner specified by 250.134 or
250.138.
Exception: For existing branch-circuit installations only where an equipment grounding
conductor is not present in the outlet or junction box, the frames of electric ranges, wallmounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes
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Land Use & Environmental Services Agency
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that are part of the circuit for these appliances shall be permitted to be connected to the
grounded circuit conductor if all the following conditions are met.
(1)
(2)
The supply circuit is 120/240-volt, single-phase, 3-wire;
or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.
copper or 8 AWG aluminum.
The grounded conductor is not smaller than 10 AWG
(3)
The grounded conductor is insulated, or the grounded
conductor is uninsulated and part of a Type SE service-entrance cable and the branch
circuit originates at the service equipment.
(4)
Grounding contacts of receptacles furnished as part of
the equipment are bonded to the equipment.
3. Is it permissible to remove the outer jacket of a listed cable and then install and use those
conductors in a metal raceway?
No. The conductors in a listed cable are to be used in accordance with its listing and labeling
instructions. See NEC 110.3(B)
4. Is it permissible to sleeve a cable with non-metallic flex in a residential mechanical closet
that has an air handler with a non-ducted return (closet space serves as the return plenum)?
SECTION 602
PLENUMS
602.1 General. Supply, return, exhaust, relief and ventilation air plenums shall be limited to
uninhabited crawl spaces, areas above a ceiling or below the floor, attic spaces and
mechanical equipment rooms. Plenums shall be limited to one fire area.
Fuel-fired appliances shall not be installed within a plenum.
602.2 Construction. Plenum enclosures shall be constructed of materials permitted for the
type of construction classification of the building. The use of gypsum boards to form plenums
shall be limited to systems where the air temperatures do not exceed 125ºF
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Land Use & Environmental Services Agency
Code Enforcement
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(52ºC) and the building and mechanical system design conditions are such that the gypsum
board surface temperature will be maintained above the airstream dew-point temperature. Air
plenums formed by gypsum boards shall not be incorporated in air-handling systems utilizing
evaporative coolers.
602.2.1 Materials within plenums. Except as required by Sections 602.2.1.1 through
602.2.1.6, materials within plenums shall be noncombustible or shall have a flame spread
index of not more than 25 and a smoke-developed index of not more than 50 when tested in
accordance with ASTM E 84 or UL 723.
Exceptions:
1. Rigid and flexible ducts and connectors shall conform to Section 603.
2. Duct coverings, linings, tape and connectors shall conform to Sections 603 and 604.
3. This section shall not apply to materials exposed within plenums in one- and two-family
dwellings.
4. This section shall not apply to smoke detectors.
5. Combustible materials fully enclosed within continuous noncombustible raceways or
enclosures, approved gypsum board assemblies or within materials listed and labeled for such
application.
6. This section shall not apply to materials exposed within equipment rooms and furnace
rooms in dwelling units.
602.2.1.1 Wiring. Combustible electrical or electronic wiring methods and materials, optical
fiber cable, and optical fiber raceway exposed within a plenum shall havea peak optical
density not greater than 0.50, an average optical density not greater than 0.15, and a flame
spread not greater than 5 feet (1524 mm) when tested in accordance with NFPA 262. Only
type OFNP (plenum rated nonconductive optical fiber cable) shall be installed in plenum-rated
optical fiber raceways. Wiring, cable, and raceways addressed in this section shall be listed
and labeled as plenum rated and shall be installed in accordance with NFPA 70
5. I was recently turned down by an inspector for having open splices on a 12 volt under
counter lighting system. The inspector stated that this was because the transformer was not
a class 2 transformer. Is she correct?
The inspector is correct. See NEC 725.46
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6. I am installing low voltage cables in a dropped ceiling. I am using J-hooks to support the
cable bundle. Are the J-hook drops required to be secured at the top and bottom, or can they
just be suspended from the top?
See NEC 300.11. If it is from a structural support, then No. If it is strictly a wire support then
yes it needs support at both top and bottom.
7. Is a disconnect required within sight of a sign or can the breaker in the panel represent
the disconnect?
Yes. See NEC 600.6(A) 1 and 2.
8. Is it permissible to install a junction box that is unsupported (example: at a cooktop
location)?
No. See NEC 300.11(A)
9. In a residence we have a sub-panel being fed with a feeder from the main panel. The
water line coming into the house is plastic then turns to copper after the meter. There are no
copper water lines in contact with the earth for more than 3.0 m (10 ft) Is it acceptable to
bond the copper water line in the residence from the feeder panel since we are only bonding
the copper lines and not grounding?
Section 250.52(A)(1) deals with the metal underground water pipe as a grounding electrode
issue. Since the water pipe is plastic, it is not covered by this section.
Section 250.104 (A)(1) requires Metal water piping system(s) installed in or attached to a
building or structure to be bonded to the service equipment enclosure, the grounded
conductor at the service, the grounding electrode conductor where of sufficient size, or to the
one or more grounding electrodes used. (Single family dwelling) In a building of multiple
occupancy, the water pipe is permitted to be bonded to the panelboard that serves only that
particular occupancy. (Section 250.104(A)(2)
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10. All of the electric ranges I am installing in an apartment building are rated 17.0 KW at
240-volts. My boss says I can use 50-ampere range cords and I say they are over 70amperes and shall be direct-wired. Who is correct?
Note 1 Table 220.55, Table 310.16, 220.61, Table 250.122, 250.138(A)
Your Boss is Correct. Note 1 to Table 220.55 requires that for ranges
individually rated more than 12 KW but not more than 27 KW, the maximum
demand in Column C shall be increased 5 percent for each additional kilowatt or
major fraction thereof by which the rating of individual ranges exceeds 12 KW.
17KW -12 KW = 5 KW
5 KW x 5% = 25% x 8 KW
(Column C) = 2 KW
8 KW + 2 KW = 10 KW
10 KW ÷ 240 V = 41.7 A
Based on this your branch circuit rating can be 50-amperes, the branch circuit ungrounded
conductors would be 8 AWG copper conductors (Table 310.16) and the grounded conductor
can be 10 AWG (Section 220.55). You need an equipment grounding conductor run with the
branch circuit conductors and it will be sized according to Table 250.122 which indicates for a
50-ampere rated overcurrent device a 10 AWG copper conductor is required or if you are
using a metal raceway, the metal raceway can be the equipment grounding conductor.
You will be required to use a 50-ampere, 125/250V, 4-wire flexible cord and matching
receptacle to comply with the grounding of the cord and plug connected equipment
requirements of Section 250.138(A).
11. I installed a UL listed bathroom fan unit that has an equipment grounding conductor
screw termination on it that I attached to. The inspector turned me down and said I had to
add a ground clip and terminate the grounding conductor to it. Why?
There are many different makes and models of bath fan on the market. It will depend entirely
on how the fan is made and the manufacturer’s installation instructions as to how the
equipment ground should be terminated.
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