effective ground

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Adams14

Adams14

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Commerce City, CO
I work in public buildings that are older where the conduit is used as fault path. There was a flood in a lunch room some 115 volt floor outlets were totally submerged and the circuit breakers did not trip, the water was boiling hot. After investigation the subpanel had no EGC and one locknut. the branch circuit from that subpanel had no EGC. I find this kind of installation all of the older buildings district. Is there a testing method measure ground paths, or a tester that cam measure ground paths. I don't feel comfortable with the direct ground test (touching energized conductor to a J-box or conduit).
 
It is not a surprise that water is not a good conductor and that the breaker did not trip. During hurricane Katrina there were basement panels submerged that were fully energized.

Run a temporary wire from the panel equipment ground bar to the floor outlets and then do a continuity test between the wire and the conduit.
 
Even with a copper wire EGC the water would not trip a standard breaker.

The boiling water is what will happen.

I see it pretty often in my service work.
 
Adams14 said:
I work in public buildings that are older where the conduit is used as fault path. There was a flood in a lunch room some 115 volt floor outlets were totally submerged and the circuit breakers did not trip, the water was boiling hot. After investigation the subpanel had no EGC and one locknut. the branch circuit from that subpanel had no EGC. I find this kind of installation all of the older buildings district. Is there a testing method measure ground paths, or a tester that cam measure ground paths. I don't feel comfortable with the direct ground test (touching energized conductor to a J-box or conduit).
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The panel and the equipment had neutrals. Additional grounding paths would not have made any difference. It is somewhat rare for water to trip breakers on 120/240 volt systems, and often not even on 480Y/277 volt systems. The water is just not conductive enough to flow enough current to open an OCPD.
 
Adams14 said:
I have heard a loop impedance meter could be used, but they are kind of pricy.
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It doesn't matter what the impedance of the grounding path is, it still won't make any difference for this issue. We don't require that type of testing here, but that is requirement of the codes in Europe. The impedance of the EGC does make a difference with a ground fault.
 
Adams14 said:
I have heard a loop impedance meter could be used, but they are kind of pricy.
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You can also use a DLRO which is gonna be easier to rent than an impedance meter.

That said, I agree with the others that this test is unnecessary: I've also seen electrical quipment running perfectly happily while completely submerged.

Water is a just-good-enough conductor to present a danger to humans, but when it comes to circuit protection it is a very poor conductor. You can even carefully demonstrate this at home: Fill a Tuperwear container with water then deliberately submerge the end of a 3-wire extension cord plugged into a GFCI; there's a good chance there won't even be enough leakage current to trip the GFCI.
 
iwire said:
Even with a copper wire EGC the water would not trip a standard breaker.

The boiling water is what will happen.

I see it pretty often in my service work.
Click to expand...

I agree!!!--We had a 480V Single Phase service panel supplying lighting loads--At times it would be in 2 feet of water --completely covering the contactors and the lights and photo cell worked fine--on at dusk and off at dawn----

It's been moved!!!!
 
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