integrity of the conduit

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Ponchik

Ponchik

Senior Member
Location
CA
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Electronologist
How does one verify the integrity of an existing underground RMC and the effective ground fault current return path if the existing installation does not have an EGC in conduit and the installation is 25 year old underground RMC.

Of course when i measure voltage I wil read 120V. but if there is fault will the 20A breaker trip in time?

Thank you.
 
The only sugesstion I can come up with short of digging it up would be to use a length of heavy gauge wire with a known resistance as an extension to the test leads on your multimeter and check the resistance from one end of the conduit to the other. There has to be a better way as the multimeter is very limited in voltage and CURRENT which will often mask problems.
I would consult NETA certified personnel for their advice.
 
IMHO ,If doing a job and I were asked to verify the equipment ground. Certainally it may be good , but for how long. And in what weather conditions. I don't think any one here would trust a 25 year old underground system. If your question is for conversation only, then surely you would have alot of discussions that may work well or not.
Otherwise we would pull new circuits.
Depending on if this is a feed for a resi outhouse light or a school shower.
 
edward said:
How does one verify the integrity of an existing underground RMC and the effective ground fault current return path if the existing installation does not have an EGC in conduit and the installation is 25 year old underground RMC.

Of course when i measure voltage I wil read 120V. but if there is fault will the 20A breaker trip in time?

Thank you.
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I don't know that you can. You might be able to induce a current from one end of the conduit to another and measure the voltage drop, but I don't know what standards there are for what an acceptable number would be.

I think there are some testing instruments that do just this.

Whether the results are meaningful or not is difficult to know. An out and out failure is meaningful, but if it passes, who knows.
 
the only way i'd put my name on the integrity of an existing conduit system would be to expose it, (like stated in the previous post) inspect it, and repair any thing that needed repair. i've seen aluminum uf ffedersd function well fir years, then start acting hinky, dug 'em up, and one leg was literally dust at some point in the run, very strange. for me, not without a visual
 
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