MECKLENBURG COUNTY
Land Use and Environmental Service Agency
Code Enforcement
2/9/11 ELECTRICAL CONSISTENCY MEETING
Code Consistency Questions
1. I have a 500 KVA generator, with no overcurrent protection at the generator, and it’s
feeding a trough. Off this trough I am feeding two 200 Amp disconnecting means. 1) How do
is size the conductors to the trough? 2) How do I size the conductors to my disconnects?
See 445.13 and 19. 445.19 (2) first of all allows a generator to feed individual enclosures
tapped from a single feeder for load separation and distribution. 1) 445.13 says if those feeder
conductors to the trough don’t have overcurrent protection ahead of them, they shall be sized
to carry 115% of the generator nameplate current rating. 2) We would then size the
conductors to the disconnects per the appropriate tap rule found in 240.21 and load
calculations per article 220.
2. Is a disconnect required within sight of a range hood controller?
Yes – No - Maybe. 422.31 & 422.32 Exception & 422.34 (D).
If the motor is 1/8 hp or less and 300 VA or less; the answer is no. (422.31(A))
If the motor is over 1/8 hp and there is no unit switch, then yes, there must be a disconnect
within sight of the controller. (422.32)
If the motor is over 1/8 hp and there is a unit switch, then the disconnect is permitted to be
out of sight from the controller. (422.31(B) & 422.34(A-D))
NOTE: A unit switch(es) with a marked-off position that is a part of an appliance and
disconnects all ungrounded conductors shall be permitted as the disconnecting means
required by this article where other means for disconnection are provided in occupancies
specified in 422.34(A) through (D).
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3. I have a lug that is attached to the meter can (not to the neutral bar which is also
attached to the can). Am I allowed to attach the grounding electrode conductor to this lug.
(see attached picture)
No. 200.2(B) states “The continuity of a grounded conductor shall not depend on a connection
to a metallic enclosure, raceway, or cable armor.”
4. In a 120/240-volt 3-phase, 4 wire, delta-connected panelboard, are straight voltage rated
2-pole breakers (240-volts) required only when one pole is connected to the high leg (“B”
phase); and are slash-rated 2-pole breakers (120/240-volts) permitted where connected to
the “A” & “C” phases?
See 240.85 that states, “A circuit breaker with a straight voltage rating, such as 240V or 480V,
shall be permitted to be applied in a circuit in which the nominal voltage between any two
conductors does not exceed the circuit breaker’s voltage rating. A circuit breaker with a slash
rating, such as 120/240V shall be permitted to be applied in a solidly grounded circuit where
the nominal voltage of any conductor to ground does not exceed the lower of the two values
of the circuit breaker’s voltage rating and the nominal voltage between any two conductors
does not exceed the higher value of the circuit breaker’s voltage rating. Therefore, a 240-volt
circuit breaker can be connected between any two phases of a 120/240-volt, 3-phase
panelboard supplied by a 120/240-volt delta 3-phase system. A 120/240-volt rated circuit
breaker may service 120-volt line-to-ground circuits and/or 240-volt line-to-line circuits. A
slash rated 120/240-volt circuit breaker may not be applied on a 208-volt line-to-ground
circuit. There is no NEC prohibition in connecting a 2-pole, 120/240-volt rated circuit breaker
between A and B or between B and C phases where the nominal voltage of any conductor to
ground does not exceed the lower of the two values of the circuit breaker’s voltage rating and
the nominal voltage between any two conductors does not exceed the higher value of the
circuit breaker’s voltage rating. The UL panelboard marking guide states, “Some circuit
breakers, like single-pole breakers for use with handle ties rated 120/240 colts, should not be
connected to the phase that is 20-volts to ground. Also the UL panelboard marking guide
goes on to state, “Generally, the B-phase is used only in conjunction with either the A- or Cphase for a 240 single-phase branch circuit or with both the A- and C-phase for a three-phase
branch circuit. Circuit breakers or cartridge fuses rated for straight 240 volt systems are
suitable for this use.”
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5. Is a bonding jumper required around a water meter when the grounding electrode
conductor is connected to the street side of the water meter?
Maybe, see 250.53(D)(1) that states, “Continuity of the grounding path or the bonding
connection to interior piping shall not rely on water meters or filtering devices and similar
equipment.” If the street side of the meter has a metal water pipe that is in direct contact
with the earth for 3.0 m (10 ft) or more and the grounding electrode conductor is connected
to that pipe on the street side of a water meter, then that pipe is adequate as a metal
underground water pipe electrode per 250.52(A)(1). However, the interior portion of the
metallic water piping system on the house side of the water meter cannot benefit from that
sole connection on the street side of the water meter, therefore either a bonding jumper
needs to be installed around the water meter to provide continuity of the metal water piping
system or a separate bonding conductor per 250.104(A) will be required to be installed to the
interior water piping system that is on the house side of the water meter. See 250.104(A)(1)
that states, “Metal water piping system(s) installed in or attached to a building or structure
shall 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. The bonding jumper(s) shall be sized in accordance with Table 250.66 except
as permitted in 250.104(A)(2) and (A)(3).”
6. Is the 10 AWG DC grounded conductor of a PV system required to have a white outer
finish or can it being re-indentified?
In accordance with 200.6(A), grounded conductors that are smaller than 6 AWG and used in
PV source circuits are permitted to be marked at the time of installation with a white marking
at all terminations. Also see 200.6(A)(2) that states “A single-conductor, sunlight-resistant,
outdoor-rated cable used as a grounded conductor in photovoltaic power systems as
permitted by 690.31 shall be identified at the time of installation by distinctive white marking
at all terminations. See also 200.6(B) and 690.13.
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7. I have a 5000 amp feeder with 12 parallel runs of 600 kcmil THHN copper ungrounded
conductors installed in 12- 4" PVC conduits. What is the minimum size copper equipment
grounding conductor required in each conduit? 600 kcmil or 700 kcmil?
For a 5000 ampere overcurrent device Table 250.122 shows a 700 kcmil. While this might
seem to qualify for the allowance in 250.122(A) where the EGC is not required to be larger
than the phase conductor, it does not apply to these conductors that are in parallel. This EGC
sizing requirement is in place because the majority of the ground fault current could be
supplied by all the phase conductors but be returned to ground by only one EGC.
8. Can you explain why the DC conductors for PV systems are sized by multiplying 125%
twice?
Section 690.8(A) requires the photovoltaic source circuit maximum current to be the sum of
parallel module rated short circuit currents multiplied by 125% (these are maximum short
circuit currents). Section 690.8(B)(1) requires the dc circuit conductors and any overcurrent
protective devices to be sized to carry the maximum short circuit currents figured at 125% in
690.8(A) plus an additional 125% for continuous use or a total of 156%. This 156% will
ensure the conductors are large enough to handle both normal current plus the additional
fault current at the point of fault from both the array at the fault site and any that are in
parallel with the array. 690.8(B)(2) Overcurrent protection for photovoltaic output circuits
with devices that will internally limit the amount of current from the photovoltaic output
circuits (for example, where fuses are built into the system) are permitted to be rated less
than 156%. These overcurrent protective devices can be rated at least at 125% of the limited
current value. The conductors must still be rated at 156%. 690. 8(D) Where a single
overcurrent device is used to protect a set of two or more parallel connected module circuits,
the ampacity of each of the module interconnection conductors shall not be less than the sum
of the rating of the single fuse plus 125% of the short-circuit current from the other parallel
connected modules.
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9. Is a disconnect mandatory both inside and outside for a mini-split system?
Yes-No-Maybe . 424.19 There are so many different makers and combinations of make-ups of
these systems that no one answer will cover them all. You will have to look at the installation
instructions first and then apply the proper Code section. It should be noted, however, that in
some cases it is allowable for the breaker in the panel to serve as the disconnect for these
units per 424.19.
10. There is a GFCI protected 125 volt 15 amp receptacle outlet installed on the front porch
of a single dwelling. I have to step up onto the porch slab 4 inches from grade to access the
receptacle. Can this receptacle be recognized as the required outside receptacle on the front
of the dwelling unit?
As the question is written, no. See 210.52(E) that states “For a one-family dwelling and each
unit of a two-family dwelling that is at grade level, at least one receptacle outlet accessible
while standing at grade level and located not more than 2.0 m (6½ ft) above grade shall be
installed at the front and back of the dwelling.” NEC 210.52(E)(3) requires a receptacle outlet
within the parameter of the porch . A receptacle can be located to meet both of these
requirements.
11. For a 240V to 208Y/120V transformer, is it better to bond the neutral to the metal frame
at the transformer itself, at the panel, or at both locations?
Better to bond at the source. There are three exceptions and one may bond the neutral at
either point as long as the neutral does not carry parallel current. See 250.30(A)(1) that
states “This connection shall be made at any single point on the separately derived system
from the source to the first system disconnecting means or overcurrent device, or it shall be
made at the source of a separately derived system that has no disconnecting means or
overcurrent devices.” Also see Exception No. 2 that states “A system bonding jumper at both
the source and the first disconnecting means shall be permitted where doing so does not
establish a parallel path for the grounded conductor. Where a grounded conductor is used in
this manner, it shall not be smaller than the size specified for the system bonding jumper but
shall not be required to be larger than the ungrounded conductor(s). For the purposes of this
exception, connection through the earth shall not be considered as providing a parallel path.”
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12. I was recently turned down by an inspector for using HCF MC cable to wire recessed and
lay-in fixtures in a hospital. I understand that non-flexible raceways are required for
emergency system wiring; but does that include whips for light fixtures, headboards, custom
office furniture and other items that are difficult to connect as well?
See 517.30 (C) (3) 3 d. After consulting with DOI and other enforcement entities, the
consensus was that lay-in fixtures (luminaires) ARE considered “necessary for flexible
connection to equipment” and thus they, along with the other equipment mentioned above,
are permitted to be installed with listed flexible metal raceways and listed metal sheathed
cable assemblies; not because they are difficult to connect but because of the need for
flexibility after connection.
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