Bare copper in EMT

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Fred B

Fred B

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Location
Upstate, NY
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Electrician
A thought came up and was wondering if there is a code restriction that would prohibit the use of a bare Copper ground wire for use in an EMT? Not that I've ever done or even seen it. Just curious why? And if there would be a logical reason not to, other than being redundant seeing EMT itself can act as an egc? What sort of complications would result if any?
 
infinity said:
An EGC within EMT is permitted to be bare copper. Not sure if there's any advantage to using it. Actually insulated conductors would be easier to pull into the EMT.
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Perhaps bare wire EGCs would also be more likely to damage the insulation on the other conductors, particularly if the bare wire was already in place and more conductors are being pulled through. But that is speculation on my part.
 
I was on a job where we pulled a lot of #6 bare stranded in PVC. I do not recommend it, go with green thhn. It likes to link, and has a higher coefficient of friction, and I could see it more prone to damaging the other conductors in the wrong situation.
 
For an EGG, no code restrictions. For a GEC, 250.64 requires bonding, easier to use PVC.
However, the IEEE green book on grounding discusses how an insulated EGC protects the other conductors from damage when it gets hot in a short circuit, this would be for PVC conduit. EMT would have a low impedance and may not have that issue.
 
What is the advantage, if any, of pulling a separate egc when running emt? Seems like it just increases fill in conduit and boxes.
 
Srv52761 said:
What is the advantage, if any, of pulling a separate egc when running emt? Seems like it just increases fill in conduit and boxes.
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It makes some people think they have done something special.
Of course there are some places that it is required

Roger
 
Srv52761 said:
What is the advantage, if any, of pulling a separate egc when running emt? Seems like it just increases fill in conduit and boxes.
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Opinions vary. I've heard multiple times recently that it's "needed" and "required by code". Truth is normally a wire type EGC is neither.
 
paulengr said:
VFDs usually require an isolated ground.
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Most of the VFDs I have seen ask for a dedicated ground conductor to a common point (no daisy chaining from device to device). I have never seen one requiring an isolated ground.
 
Srv52761 said:
What is the advantage, if any, of pulling a separate egc when running emt? Seems like it just increases fill in conduit and boxes.
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If a connector or coupling comes loose, you've lost your EGC path. All it takes is for one set-screw to drop out due to some vibrations. The wire-type EGC serves as a practical back up.

Happens all the time. People put their feet up on exposed work, sit on it for a break, etc.

The first time I ever heard of it was on a residential project covered by the 2017 code. I thought it was a new 2017 requirement, but it was just spec'd that way. After thinking about it for a bit, it actually makes sense.

I ALWAYS pull a wire-type EGC in my EMT for this exact reason.
 
Jerramundi said:
If a connector or coupling comes loose, you've lost your EGC path. All it takes is for one set-screw to drop out due to some vibrations. The wire-type EGC serves as a practical back up.
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cant the same thing happen to a wirenut on a egc connection? Besides its highly unlikely you will loose the egc path just because of a loose set screw.

Not sure when so many people became obsessed with redundant grounds. No one uses redundant GFCI's, AFCI's, OCPDs, etc.
 
retirede said:
A reasonable alternative would be to properly assemble the raceway.
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I take offense to the implication that I would do anything less than that. For the record, I double check EVERY SINGLE set screw TWICE. I tighten as I go and then go over my raceway a second time EVERY SINGLE TIME giving EVERY set-screw a second crank with a flat-head because I feel it provides more torque and as a means to double check my own work because I am only human.

You can assemble the raceway PERFECTLY... that doesn't stop people from putting their feet up on it, sitting on it, HANGING BENDERS ON IT, or prevent loosening over time due to vibrations and such, etc.

The simple fact of the matter is, if that raceway comes apart FOR WHATEVER REASON, you've lost your ground fault current path... and that wire-type EGC that maintains that ground fault pathway when a piece of pipe is hanging out of connector might just save a life.

Therefore, there IS a practical purpose behind a wire-type EGC in a metal raceway.
 
In my case, with residential I'm mostly working with 15A-30A circuits. So adding that extra wire is fairly cheap.

I can see cost effective arguments start to have merit when you get into larger wire types, but even then, the increased cost doesn't negate the logic provided above, which is that if that pipe comes loose for whatever reason, you've lost an essential safety measure and that back up wire-type EGC might just save a life.
 
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