This article was posted 05/16/2006 and is most likely outdated.

NEC Questions and Answers - May
 

 
Topic - NEC Questions
Subject - NEC Questions and Answers - May

May 16, 2006  

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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.”

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Comments

  • Do you have to strap pipe within 3 ft of a coupling the code says within 3ft of tubing termination is a coupling a tubing end point

    Anthony
    Reply to this comment

  • Your response to Q4 - about the minimum distance for a transformer, did not seem complete enough for me. I felt you should have specified that your answer referred to dry type transformers and that oil filled transformer restrictions are different, especially if the wall has doors or windows. Or maybe the question should have been presented differently, specifying the dry type transformer and an inside the building wall.

    Mary Ann Ruopp
    Reply to this comment

  • Regarding the answer to Question 5:

    Receptacles are NOT required behind doors with a 24" or more swing. 250.52(A)(1) states that receptacles shall be installed so that, "...no point measured along the floor-line in any wall space is more than 1.8m (6ft) from a receptacle outlet".

    250.52(A)(2) defines wall space, "Any space 600mm (2ft) or more in width (including space measured around corners) and unbroken along the floor lines by doorways, fireplaces, and similar openings."

    In other words, the receptacle does not have to be located in that space behind the door, only that the space has to be included in the wall-line measurement.

    erin

    Erin Winter
    Reply to this comment

  • Mike - I really enjoy the information from your website. The question and answers are especially useful. I oversee 11 electricians for Baltimore County Government. We do maintenance and installations for over 500 sites, including Police and Fire stations, and our 911 Communications Center. I review the questions and answers with my electricians. They find them very informative. Thanks again, Tom Ercole.

    Tom Ercole
    Reply to this comment

  • Hello Mike, I must disagree with Q&A number 5. A outlet is not required behind the swing of a door, unless the door and swing is more than 6 feet. The wall space behind a door swing is included when measuring the wall space for compliance with spacing in NEC 210.52(A)(1). A better answer would have been...... "The space behind a door swing is included in the wall measurement..no space along the wall more than 6 feet from an outlet... when complying with NEC 210.52(A)(1), Wall Spacing

    Ray McGinty
    Reply to this comment

  • Concerning the answer A10, I am probably unclear on the concept, but supposing the genset were of the mobile type (rubber tires). and a ground fault occured involving the genset only, (transfer switch on lineside), and the genset was not equipped with GFCI, wouldn't this create a potential hazard? Thanks, Mark

    Mark
    Reply to this comment

  • In response to the generator question in this month's Q & A, Generator ground rods should bond the frame of the generator only. The Neutral should not be bonded to such a ground as per code but the generator itself being a metal enclosure with energized parts is required to be bonded. At least that's one inspector's opinion.

    Rick

    Rick Fornataro
    Reply to this comment

  • i would like to thank you for having a website such as this. it helps so many things specially to our colleagues by proffession. i am hoping that you will continue your vision to help electrical practioner in practicing electrical works in a safe and as per code manner.

    Mark R. Guillermo
    Reply to this comment

  • What is the right method to compute the KAIC interrupting capacity of a bus?

    Mark
    Reply to this comment

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