EMT as a ground path

Status
Not open for further replies.
I

Ironwood

New member
Location
Atlanta, GA, MAGA
I once had a copy of a Georgia Tech research paper that concluded that a long run of 1/2" EMT was a better ground than a #12 wire. Through testing they found that adding a redundant ground wire to this EMT did not decrease the fault clearing time of a short circuit. I had it saved on my computer, but that was many computers ago. I once included it in correspondence with an engineer about why a redundant #12 ground is not required in EMT by the NEC, excluding health care facilities of course. He still demanded it, so I asked if he also wanted two equipment ground conductors in PVC.

At any rate, I've lost that research paper and wondered if anyone here had a link to it or a similar study. I've found a powerpoint presentation that refers to the GT study, but it isn't the original.
 
People that want a wire EGC inside metal raceways want it because they are afraid of a loose fitting compromising the EGC path, which is a legitimate concern, but so is a loose termination on the wire type EGC.

My guess is this loose fitting concern is at least somewhat of a driving factor for the health care EGC requirements.
 
I have come across many loose fittings and loose locknuts in EMT. I personally don't trust EMT conduit to be a good ground. Apparently neither does one of the counties I work in because they have an amendment requiring a ground wire. IMC and RMC is more likely to be well grounded but I have come across many non-wrench tight connections with those as well e.g. when installing a 90 in RMC you almost always have to back it off a bit to get it to face the correct direction.
 
Coppersmith said:
I have come across many loose fittings and loose locknuts in EMT. I personally don't trust EMT conduit to be a good ground.
Click to expand...
EMT is an excellent ground fault path, better than any wire you can stuff in it. What you are talking about is poorly installed EMT. I've seen plenty of poorly installed wire EGC. I work on buildings with thousands of feet of EMT and there's not a problem with any of it.
Apparently neither does one of the counties I work in because they have an amendment requiring a ground wire. IMC and RMC is more likely to be well grounded but I have come across many non-wrench tight connections with those as well e.g. when installing a 90 in RMC you almost always have to back it off a bit to get it to face the correct direction.
Click to expand...

The Cult of the Green Wire is relentless and their power is growing. Very, very sad to hear they have taken over an entire county.
 
ActionDave said:
EMT is an excellent ground fault path, better than any wire you can stuff in it. What you are talking about is poorly installed EMT. I've seen plenty of poorly installed wire EGC. I work on buildings with thousands of feet of EMT and there's not a problem with any of it.


The Cult of the Green Wire is relentless and their power is growing. Very, very sad to hear they have taken over an entire county.
Click to expand...

electrofelon said:
There are many locations in a raceway system where, if a fault were to happen - even with a wire egc - the fault will have to travel through the raceway.
Click to expand...

I agree with both of you and so does the NFPA

Roger
 
ActionDave said:
I work on buildings with thousands of feet of EMT and there's not a problem with any of it.
Click to expand...

I can see you are passionate about this issue, but are you sure you are not overstating the reliability of all those EMT couplings a bit?

I would not bet my life on the quality of work done by some random electrician and the random events that have happened to that pipe over the years.
 
Jamaica used to not require a ground wire, under the idea that the steel would be the ground. But, now they are requiring a ground and are preferring to see PVC used because they finally admitted that steel or EMT can rust in concrete and the ground can then disappear... but they still require that the ground go back to the panel, even though they have all the rebar in the buildings... and even though they have been shown that the ground is continuous no matter where you touch the rebar in the building as long as it was twist tied properly and then encased by concrete rather than just stuck in the CMU...
 
Coppersmith said:
I would not bet my life on the quality of work done by some random electrician and the random events that have happened to that pipe over the years.
Click to expand...
And random events are pretty much the reason the NFPA sees the raceway as the primary EGC and the wire a measly backup.

In a commercially constructed building with all the metal involved you could randomly remove sections of EMT and still have a low impedance fault clearing path whereas one loose connection of a wire you loose it.

Roger
 
Coppersmith said:
I can see you are passionate about this issue, but are you sure you are not overstating the reliability of all those EMT couplings a bit?

I would not bet my life on the quality of work done by some random electrician and the random events that have happened to that pipe over the years.
Click to expand...
I agree with both the cats.

Reliability of the fittings isn't the problem, installers are the problem if it is going to fail.

Most the time when I see broken fittings, it is usually not supported properly, which contributes to breaking more easily.

Forgetting to tighten set screws or compression nuts is just carelessness by the installer. Same carelessness can happen with making up EGC's and you still end up with lesser quality installation.

If you are installing on all steel construction and do miss tightening a fitting - kind of doesn't matter anyway - but a good installer still rarely misses tightening a fitting.
 
Sloppy work installing the EMT is easier to spot. I think that's why it's considered more likely and more common.

Sloppy work inside a box is just as easy and, IMHO, just as common. It's just not as readily visible.
 
Status
Not open for further replies.
Top