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I have read here that metal conduit can be used as the ground and you needn't then pull a separate ground wire:

  • What are the NEC rules governing this?

  • How do you avoid "weak ground" links between conduit segments?

  • Are there safety considerations?

  • Do you have to clamp bond wires between segment couplers, or should the couplers and their interface to the conduit be sufficient?

  • Do ground-conduits need to be rated as such?

  • Other considerations?

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  • Is this indoors, outdoors, on a roof where the conduit will get stepped on? Are we talking about threaded conduit (rigid/RMC/GRC and IMC), or non-threaded conduit (EMT)? Also, we're talking about voltages less than 250V to ground, right? Apr 14 at 1:08
  • You seem positively incredulous. But I feel about the same about plastic boxes... how can that be legal or safe? Apr 14 at 1:09
  • @ThreePhaseEel, mostly indoor through an attic space, but starts outside in a NEMA 3R box. Haven't decided on conduit type, was just doing some research and was surprised that there were options to use conduit as a ground.
    – KJ7LNW
    Apr 14 at 19:13
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What are the NEC rules governing this?

You are not allowed to use any wiring method, except for specific wiring methods listed (enumerated) in the back half of NEC Chapter 3. (The Article 300s). Therein, you will find an article for each allowed wiring method.

Where a wiring method allows use of the pipe as the ground, it will specifically say so in that article.

Select an appropriate wiring method.

Note that you can change wiring methods anywhere appropriate, such as from EMT to NM at a junction box, or EMT to Rigid at any appropriate coupler.

In a few cases you can also use a wiring method inside a wiring method, e.g. you could carry NM-B past the first junction box in conduit, through the conduit, to the second box and splice it there, if the conduit is large enough to allow this. Just in case you're all out of THHN wire :)

do ground-enabled conduits need to be rated as such?

Not as "ground-enabled" (your term), no.

However the conduit must be rated and UL listed for the wiring method which you are using. If you select the IMC wiring method, you must use pipe listed and labeled as IMC.

If you are working up a plan to use leftover plumbing or general-use pipe as a wiring method, forget it, but it may be usable as a damage shield for another wiring method such as UF which needs one.

How do you avoid "weak ground" links between conduit segments?
Are there safety considerations?

By following the rules for the wiring method, and NEC 110.2 which requires you use [UL] approved equipment, and NEC 110.3(B) which requires you obey labeling and instructions of equipment.

If you do all that, then the NFPA Code committees and UL have done all the heavy lifting for you.

Do you have to clamp bond wires between segment couplers, or should the couplers and their interface to the conduit be sufficient?

You need to follow the NEC article for the wiring method, and other NEC rules as may be applicable. For instance if you bring 1” conduit into a 1-1/2” knockout, using adapter washers, you must provide for ground continuity some other way.


Lastly if the installation is making you nervous, review your understanding of Code regarding the part that makes you nervous. If it still makes you nervous, throw a ground wire in the pipe.

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Rules may be different for state. Not every metal conduit approved as ground. In Ontario, for instance, only EMT with screw type couplings and connectors approved as proper ground. Using compressed connectors, ground wire should be pulled. If you are not know for sure, pulling ground wire is better then not pulling.

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  • @Harper I am not guessing. It is from practice. And compressed couplings are required in damp location and then using it, EMT is not accepted as ground. Ground wire has to be.
    – user263983
    Apr 14 at 11:38
  • Sorry I misunderstood, I did not realize you were saying "rules may be different for 'The States' as in "that slightly smaller country south of the border". Apr 14 at 16:57
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    @Harper-ReinstateMonica By states I mean states, not "The States". NEC is on top but different states may is having their own rules. They have different environment conditions. It can not be same in Alaska and Florida. CE code is pretty same and in Ontario ( it is canadian province) we have own code.
    – user263983
    Apr 14 at 19:59

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