conduit as equipment grounding conductor

[petersonra]

Code allows conduit as ECG, but I'd tighten the nuts and add ground-bushings and wire at each end especially if you're going to be using AFCI or GFCI from that panel. (a ground fault will have to travel all the way to the main panel to sense) I figure if NEC doesn't allow just the electrical nuts at the service why would I allow it for a sub panel? That being said I find conduit to be pretty reliable ECG as long as all the fittings and nuts are tight.

I don't see how AFCI or GFCI has anything to do with it. They will trip far more reliably on a GF condition than will a normal circuit breaker that relies on a high level of current to trip.

 

[DaveTap]

Yes, ground wire is supplementary and not required... but I've seen continuity problems between conduit and boxes...especially aluminum conduit. Shorts won't have trouble overcoming a poor connection, GFCIs on the other hand...
Ground bushing and wire is CHEAP insurance.

Oh and yes I was talking about bonding to make sure conduit is an ECG.

 

[DaveTap]

I don't see how AFCI or GFCI has anything to do with it. They will trip far more reliably on a GF condition than will a normal circuit breaker that relies on a high level of current to trip.

I think GFCI test button shorts neutral to EGC.
All I know is if there's no ground it won't trip and I've seen intermittant grounds and long conduit runs cause them to not test correctly and/or false trip. The newer ones seem less prone to these issues, but...

 

[don_resqcapt19]

David,

I think GFCI test button shorts neutral to EGC.
All I know is if there's no ground it won't trip ...

That is not correct. The test button on the GFCI does not require an EGC to function. The test button puts a resistor between the hot and the neutral, but the connections are on opposite sides of the current sensing device creating the 4-6 mA inbalance required to trip the device. If you are using a plug in tester, then the tester won't function without an EGC.
I can't imagine a metallic conduit that is in such poor condition that it can support the flow of less than 10mA.
Don

 

[infinity]

Small point - NEC REQUIRES metallic conduit to serve as ground. The ground wire is supplementary.

Couldn't I have a run of metallic conduit with a section of non-metallic conduit in the middle of it?

 

[iwire]

I think what he meant was that if you use metallic conduit it is an EGC and has to be bonded so it is an EGC.

That is what I suspect as well....and it is not true.

As Trevor has pointed out I might switch from metallic conduit to PVC in the middle or at one end.

In that case the conduit is not an EGC, it is not required to be an EGC although it is required to be bonded.