MECKLENBURG COUNTY
Land Use and Environmental Service Agency
Code Enforcement
8/10/11 ELECTRICAL CONSISTENCY MEETING
Code Consistency Questions
1. Is low voltage cable allowed to be run through drilled holes in wood studs along with
normal 15 and 20 amp branch circuits in a single family dwelling?
Maybe and Yes. Per 725.136 there are many instances where the two are not allowed to be
run together; however at 725.136(I) it states:
I) Other Applications. For other applications, conductors of Class 2 and Class 3 circuits shall be
separated by at least 50 mm (2 in.) from conductors of any electric light, power, Class 1 non–
power-limited fire alarm or medium power network-powered broadband communications
circuits unless one of the following conditions is met:
(1) Either (a) all of the electric light, power, Class 1, non–power-limited fire alarm and
medium-power network-powered broadband communications circuit conductors or (b) all of
the Class 2 and Class 3 circuit conductors are in a raceway or in metal-sheathed, metal-clad,
non–metallic-sheathed, or Type UF cables.
(2) All of the electric light, power, Class 1 non–power-limited fire alarm, and medium-power
network-powered broadband communications circuit conductors are permanently separated
from all of the Class 2 and Class 3 circuit conductors by a continuous and firmly fixed
nonconductor, such as porcelain tubes or flexible tubing, in addition to the insulation on the
conductors.
2. I ran a 50a circuit to a wall mounted oven and tapped a #10 to feed a counter-mounted
cooking unit. The inspector turned me down and said this was only for the factory leads that
came with the oven. Is this correct?
Per NEC Article 210.19(A)(3). This is not totally correct.
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210.19(A)(3) covers factory-installed and field-installed tap conductors. The supply conductors
included in a factory-installed pigtail are considered to be tap conductors in applying this
exception. As illustrated below, this exception permits a 20-ampere tap conductor from a
range, oven, or cooking unit to be connected to a 50-ampere branch circuit if the following
four conditions are met:
1.
2.
3.
4.
The
The
The
The
taps are not longer than necessary to service or permit access to the junction box.
taps to each unit are properly spliced.
junction box is adjacent to each unit.
taps are of sufficient size for the load to be served.
3. Is a ground rod required to be driven when a generator is installed to feed a building as
a NON-separately derived system? What if it’s a separately derived system.
No, Yes. (See Attached)
System Bonding Jumper 250.30(A)(1)
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•
•
•
•
•
Connects the equipment grounding conductors of the derived system to the grounded
conductor of the derived system.
The system bonding jumper is sized in accordance with 250.28(A) through (D) based on the
size of the derived phase conductors.
Sized per Table 250.66 or 12½% rule if derived phase conductors exceed the values in Table
250.66
Locate system bonding jumper inside source enclosure or at any point to and including the
first disconnecting means or OC device of the system
The point of connection shall be made at the same point as the grounding electrode conductor
connection to the system
4. During an inspection of a new restaurant located in a mall, there is a shaft for rooftop
equipment and there is no way to enter the shaft for installation of raceways. The contractor
wants to install five runs of ½” flexible metal conduit with a maximum of four # 12 AWG
conductors. Section 348.30(A) Exception permits flex to be unsupported where fished. Do
product standards limit the maximum weight a flex connector can withstand and is this
installation permitted? If permitted is there a maximum vertical length flex can be fished?
It appears that the language in 348.30(A) does permit FMC to be unsecured and unsupported
when fished. Also unless the shaft is one of the areas not permitted by 348.12 and it appears
it is not, then the NEC would permit it. There are rules for conductor support in 300.19. The
UL white book PG 115 does not address the pull out requirements however; UL 514B requires
a 50 lbs pull for 5 minutes for FMC connectors. To me, this is a classic decision for the AHJ on
site. I don't believe that the CMP intended the unsupported length to be open ended. In
response to your FMC question, the UL pullout requirement for the 1/2 size is 75 lbs. I would
think that the length of the run would be a major consideration for this installation. Obviously
the longer the run the more weight the connector would have to contend with.
5. At a 4-story hotel, we are installing 480-volt feeders up to each floor and the design calls
for the grounding electrode conductor for the transformers to be installed in the power wiring
conduit that feeds into the transformer disconnect at each floor. The bonding is done in the
transformer. The building is poured concrete so the grounding electrode system consists of
the underground water piping and the concrete encased electrode. The power wiring is
installed in PVC conduit with an equipment-grounding conductor. Doesn’t the NEC require the
GEC to be run separately?
No, as long as all the applicable Code rules are followed. For the raceway aspect that is the
majority of the question, section 250.64(B) covers this. The grounding electrode conductor
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can be installed in the power conduit, in a separate conduit where physical protection is
required or open where protection from physical damage is not necessary. If any of the
raceway parts or enclosures are ferrous metal then those parts must be bonded at the entry
and exit to the grounding electrode conductor per 250.64(E). The other key part is
terminations. The question states the connection is in the transformer and that is fine, but the
connection where the feeder originates has to be considered. To meet the definition in Article
100 and section 250.24 the end of the grounding electrode conductor at the beginning of the
feeder must be connected directly to a grounding electrode or to a common grounding
electrode conductor by one of the connection means specified in 250.70.
6. I need to supply four 40-amp, 3-phase, 120/208 receptacles. These receptacles are all
adjacent to one another but the supply panel is quite some distance away. There is an
existing unused 90-amp (#4's & #8 ground) set of conductors less than 10 ft. from the
proposed new receptacles. The nameplate ampacity rating for each appliance is 25 amps
(ovens). Am I correct in understanding that the 10 ft. tap rule can be used to supply the new
receptacles provided that the tap conductor’s ampacity is not less than the combined
calculated loads of the tap feeder? If the tap conductors are individually routed properly, do I
need to provide an additional disconnecting means for these individual openings other than
the receptacles themselves? These commercial ovens are considered to be non-continuous
loads.
The installation method in this question does not meet NEC compliance. If the following code
sections are adhered to however, this installation is possible. 220.14 (A) [Specific Appliances
or Loads] requires the branch circuit loading to be calculated based on the equipment rating.
In this case the branch circuit would need to be rated for 100 amperes (4 @ 25 amps) not 90
amperes. 210.19 and 210.19(A)(4) require the branch circuit conductors to have an ampacity
not less than the maximum load served for non continuous loads. Receptacles (not outlets)
are mentioned in the question, so I’m assuming the ovens are cord and plug connected and
also portable. Section 210.19(A)(2) requires the conductors serving more than one receptacle
to have a rating not less than the rating of the branch circuit.
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7. I ran a raceway (tucked in a corner) up the entire length of a stairwell in a five-story
building. The raceway was for some new signs on the outside of the building. The Building
Inspector red-tagged it without leaving any explanation. Is this a violation of the NEC? If not,
what code is it from?
NO. Not an NEC violation. However there are many instances when the applicable building
codes prevail. Building codes do not allow anything in stairwell shaft enclosures unless they
are related to the stairwell. Example lighting, Fire Alarm etc. In the ICC building code sections
are 707.8.1 “Prohibited penetrations. Penetrations other than those necessary for the purpose
of the shaft shall not be permitted in shaft enclosures”
8. We have quite a bit of abandoned low-voltage communication cable in our facilities. Where
are the requirements in the NEC to remove this cable? When do cables have to be removed?
As a general rule, where the majority of the ceiling tiles are removed or replaced during the
project that portion of the ceiling shall have all abandoned cables removed and / or
supported and tagged for future use. The remaining cables shall be properly supported.
Section 640.3(A) for Audio Cable, Section 645.5(D)(6) for cables in Information Technology
Equipment spaces, Section 725.3(B) for Class 2 & 3 Circuits, Section 760.3(A) for Fire Alarm
Cables, Sections 770.3(A), 770.154(A) & 770.154(B)(1) for Optical Fiber Cables and
Raceways, Sections 800.3(C), 800.154(A) & 800.154(B)(1) for Communications Circuits,
Sections 820.3(A), 820.154 (A) and 820.154(B)(1) & (D) for CATV systems, Section 830.3(A)
for Network-powered Broadband cables.
9. If service drop conductors are increased in size due to voltage drop, is it required to
increase the size of the grounding electrode conductor?
No, 250.66 it must be sized based on the SE conductors not the service drop conductors.
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