tying ground to neutral

[frankmoon]

First let me 'sline a few things. I am a graduate retired EE but do not and have not worked NEC requirements directly for many years. Second, I think my original question on risk was perfectly valid. As I understand it, NEC did not explicitly state that tying ground to neutral was a no-no until 1996. This is a fairly late prohibition. Earlier, it was permissible to a tie groungd to neutral for a variety of reasons and one seemed to think it was risky. Until recent changes, neutral was tied to ground at the service panel so, it seems that there should be little risk. The claim that I read is that the neutral could be broken so causing a risk -- that I understand. But, a break in the gound doesn't cause a risk? Maybe I can't see all the possible connections.
I see and hear from a variety of building inspectors and electricians conflicting interpretations. For that, I don't have a lot confidence.

Finally, an ungrounded GFCI does provide some protection but such things as a shunt mode surge protector won't do what it is supposed to do. (I don't think shunt mode surge protectors don't work anyway but this is a different discussion.)

Does NEC allow an ungrounded GFCI with 3 prongs to be installed? That was my original question.

I came to this site because I can't find clear answers and explanations elsewhere.
I am a simple repair DIYER but beyond simple switch/receptacle replacement, I rely on ticket bearing electricians.

marion moon

 

[dereckbc]

Re: tying ground to neutral

Originally posted by frankmoon:

Does NEC allow an ungrounded GFCI with 3 prongs to be installed?

I will answer your question. YES, provided it complies with 406.3(3)(c). Which basically says the receptacle shall be clearly marked "NO EQUIPMENT GROUND".

I noticed earlier your thread was closed. Please do not take offense, if we error, it is on the side of caution.

Regards,

Dereck

 

[jwelectric]

Re: tying ground to neutral

250.142 Use of Grounded Circuit Conductor for Grounding Equipment.
(A) Supply-Side Equipment. A grounded circuit conductor shall be permitted to ground non?current-carrying metal parts of equipment, raceways, and other enclosures at any of the following locations:
(1) On the supply side or within the enclosure of the ac service-disconnecting means
(2) On the supply side or within the enclosure of the main disconnecting means for separate buildings as provided in 250.32(B)
(3) On the supply side or within the enclosure of the main disconnecting means or overcurrent devices of a separately derived system where permitted by 250.30(A)(1)

(B) Load-Side Equipment. Except as permitted in 250.30(A)(1) and 250.32(B), a grounded circuit conductor shall not be used for grounding non?current-carrying metal parts of equipment on the load side of the service disconnecting means or on the load side of a separately derived system disconnecting means or the overcurrent devices for a separately derived system not having a main disconnecting means.

 

[charlie b]

Re: tying ground to neutral

Originally posted by frankmoon: I think my original question on risk was perfectly valid.

I agree. That is why I gave you what I had hoped would be a clear and complete answer. If you have any questions about that answer, feel free to ask for clarification.

Does NEC allow an ungrounded GFCI with 3 prongs to be installed? That was my original question.

I think that has been answered now. If you need additional information on, for example, how to install a GFCI receptacle in a system that does not have a ground wire, then you will not get it here.

I came to this site because I can't find clear answers and explanations elsewhere. I am a simple repair DIYER but beyond simple switch/receptacle replacement, I rely on ticket bearing electricians.

This site is not intended to give clear answers and explanations to assist persons who are not electricians to perform their own electrical installation work. This site is intended to help all members of the electrical industry, including electricians, electrical contractors, engineers, designers, inspectors, and maintenance personnel, perform their job-related duties.

You are welcome to use this Forum to learn whatever you want to learn, but we cannot offer advice or assistance on performing electrical installation work at your own home. We are not permitted to assist a DIY in any way. Our concern is that you may get only the answer to the question that you ask, and get no answer to the thousand other questions that you should have asked, but did not know that you needed to ask. The Owner and Moderators of this Forum do not wish to risk allowing you and your family to be placed in danger, by giving you too little information.

 

[LarryFine]

Re: tying ground to neutral

Originally posted by frankmoon:
Earlier, it was permissible to a tie groungd to neutral for a variety of reasons and one seemed to think it was risky.

This was only really allowed on a few circuits, such as those supplying range/stoves/ovens and clothes dryers, and then only if fed via either SE cable or a cable with an insulated neutral, both of which reflect permissable uses of a current-carrying neutral conductor.

Until recent changes, neutral was tied to ground at the service panel so, it seems that there should be little risk.

The neutral/EGC interconnection in services is still required/allowed. Keep in mind that this is at the main service disconnect, which may be either in, or ahead of, the service panel.

Finally, an ungrounded GFCI does provide some protection but such things as a shunt mode surge protector won't do what it is supposed to do.

Not true: a line-to-neutral or line-to-line overvoltage clamping circuit is functional even without an EGC. Lightning protection, however, does benefit from a properly-run low-impedance earth ground.