ECN Forum Forums General Topics of the Trade General Discussion Area 2 circuits in EMT with one using wire as ground

I’m wiring a metal building with EMT raceway and THHN conductors. It’s a detached building with a 100amp “sub panel” fed from the nearby house. One branch of the EMT carries two circuits (one lighting and one RV outlet). The lighting circuit has a 12 AWG equipment ground running to all lights and connected to 3 J boxes. The RV circuit uses the EMT raceway for equipment ground. The inspector said everything has to be one way or the other. So no mixing of ground types. I can’t find any code section that agrees or disagrees with him. I’m going to just pull all the equipment ground wire out and use the raceway as the easiest solution but I would like to know if anyone can point me to something that supports his assertion. I didn’t wire it this way but I’m finishing it.

I don't know how he came up with that.
I read 250.118 I see "a combination of the following", implying you can use any of these in combination. Maybe he is looking at something else. I suppose the option is to hook a #8 to that #12 and pull it through satisfying the 100a circuit and also covering the smaller one but I don't think it is necessary by the code I use.

I agree with Greg but I think you might be up against the old adage that you can't fight city hall.

Inspectors enforcing things that aren't in the Code isn't uncommon, but Inspectors that admit they're wrong are hard to find...except for those with class who are always the first to admit their errors.

I'm going to go out on a limb here and say that maybe the Inspector is right.
Even though it is EMT, I would still run a separate ground conductor, just to satisfy actual resistance values.

The issue seems to be does the supplemental green wire ground need to satisfy 250.122 even though the EMT itself already does.
It does occur to me he can shut the inspector down if he installs an IG receptacle on the 120/20a circuit connected to the green wire. (In a plastic box)

gfretwell

Where does a plastic box come into it? They are not permitted in any run of metal raceway unless the box is fitted with a listed means of assuring continuity between its KOs, if fitted with KOs. Given the code language I wouldn't think that a field installed bond could satisfy the prohibition against the use of Nonmetallic boxes for metal raceways.

314.3 Nonmetallic Boxes. Nonmetallic boxes shall be permitted only with open wiring on insulators, concealed knob and-tube wiring, cabled wiring methods with entirely nonmetallic sheaths, flexible cords, and nonmetallic raceways.
Exception No. 1: Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables.
Exception No. 2: Where integral bonding means with a provision for attaching an equipment bonding jumper inside the box are provided between all threaded entries in nonmetallic boxes listed for the purpose, nonmetallic boxes shall be permitted to be used with metal raceways or metal armored cables.

Since Isolated Ground Receptacles do not have the grounding port of the receptacle bonded to the mounting yoke I don't see what a plastic box would achieve either.

--
Tom Horne

I couldn't agree more. The times the inspector found something they didn't like I wouldn't argue with them. Often it was something small and I'd start making the changes while they were there. They knew it would be done the way they wanted and there was no need to reinspect it. Establish that repour and it will get you a lot further.