NEC Questions and Answers
By Mike Holt for EC&M Magazine
Q1. If an outdoor hot tub has integral GFCI protection, do I still need to provide GFCI for the equipment?
A1. Additional GFCI protection isn’t required for a listed self-contained spa or hot tub unit or listed packaged spa or hot tub assembly marked to indicate that integral GFCI protection has been provided for all electrical parts within the unit or assembly [680.44(A)].
Q2. Can copper wire be used to secure EMT in a metal stud wall?
A2. Probably not. Electrical metallic tubing must be securely fastened within 3 ft of every box, cabinet, or termination fitting, and at intervals not exceeding 10 ft [358.30]. The NEC doesn’t spell out specifically how the support it to be done, but all installations must be “approved” by the AHJ [90.4].
Q3. Is a service disconnecting means required to be installed on the outside of a building?
A3. This is a judgment call by the AHJ. The service disconnecting means must be placed at a readily accessible location either outside the building or structure, or inside nearest the point of service conductor entry [230.70(A)(1)]. Check with the AHJ on what “nearest the point of entry” means, so some it means a back-to-back installation, to other they permit up to 10 ft of service conductor within the building.
Q4. What is the minimum distance a transformer must be from a wall?
Q4. Transformers rated 112.kVA or less must be at least 12 in. from combustible materials, unless separated by a heat and fire resistant barrier [450.21(A)]. Transformers with ventilating openings must be installed so that ventilation is adequate to dispose of the transformer full-load losses without creating a temperature rise that is in excess of the transformer rating [450.9].
As always, be sure to comply with the listing requirements [110.3(B)] for your particular installation, typically 6 in. of clearance is required.
Q5. When determining the placement for receptacles in a dwelling, is a receptacle required to be installed in the space behind the swing of a door?
A5. Yes, if the space behind a door swing is 24 in. or more in length [210.52(A)(2)].
Q6. Can I gang three extension rings on to each other?
A6. Yes. According to the UL listing requirement, extension rings are listed as a Metallic Outlet Boxes (QCIT) and this standard allows one or more extensions to be used [110.3(B)].
Q7. Do I have to identify GFCI protected receptacles with the “GFCI Protected” stickers that come with the devices?
A7. Yes if the instructions supplied with GFCI protected receptacle state that the enclosed “GFCI Protected” labels be placed on all GFCI protected receptacle [110.3(B)].
Q8. When GFCI protection is required by the NEC for receptacles, must I use receptacles of the GFCI type, or can I protect the receptacles on circuit with a GFCI circuit breaker?
A8. A GFCI type receptacle or a GFCI circuit breaker can be used to provide the protection required by the NEC.
Q9. What type of fitting can I use to terminate ground wires in a metal box?
A9. The termination of equipment grounding and bonding conductors must be by exothermic welding, listed pressure connectors of the set screw or compression type, listed clamps, or other listed fittings [250.8]. In addition, equipment grounding (bonding) conductors that enter a metal box must be bonded to the box by a screw or device (like a ground clip) that is not used for any other purpose [250.148(C)].
Q10. Does the NEC specifically state that a generator must be grounded to the earth if its wiring is connected to the premises via a transfer switch that does not open the neutral?
A10. According to the grounding requirements of the NEC, the answer is no, since it would serve no purpose to do so. But many generator manufactures have boiler plate instructions specifying how they want the generator grounded. Because the instructions specifically require grounding, you have to waste the time and money to drive a ground rod [110.3(B)].
It’s unfortunate that many generator manufactures don’t understand the principles of grounding and the NEC requirements for such equipment. I hope that one day the generator manufactures would simply state that the generator must be grounded in ‘accordance with the NEC.”
