Neutral fault test problems

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redarchflash

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I have a commercial occupancy where I'm required to do a neutral fault test my test is showing up with 193 ohms that I cannot get to drop at any point any suggestions on what would be causing this. I have already run through the entire building and made sure that the neutrals and grounds are separated. 3phase 4 wire 208/120 volt 1200 amp.
 
redarchflash said:
I have a commercial occupancy where I'm required to do a neutral fault test my test is showing up with 193 ohms that I cannot get to drop at any point any suggestions on what would be causing this. I have already run through the entire building and made sure that the neutrals and grounds are separated. 3phase 4 wire 208/120 volt 1200 amp.
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What two points are you measuring the 193 ohms between?

Even if you have lifted the main bonding jumper at the service disconnect there will be a bond between neutral and earth ground at the POCO transformer secondary.
 
ptonsparky said:
The neutral you are testing is disconnected from all other wires? It has been removed from the neutral bar(s) entirely? Check again. Is any of this buried?

You should be reading in the megaohms or higher
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Exactly.

Testing for continuity between the lifted neutral and ground is to verify there are no neutral-to-ground faults during normal operation.
 
Smart $ said:
Exactly.

Testing for continuity between the lifted neutral and ground is to verify there are no neutral-to-ground faults during normal operation.
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And if you leave equipment connected, even with branch or feeder breakers open, you will be picking up neutral to ground faults in any of the connected equipment, not just in the wiring itself.
But the reading you get suggests a pinched or scraped neutral wire somewhere.
By lifting feeder and branch neutrals you can zero in on the location of the problem.
 
GoldDigger said:
And if you leave equipment connected, even with branch or feeder breakers open, you will be picking up neutral to ground faults in any of the connected equipment, not just in the wiring itself.
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Roger that, and removing loads may be impractical when power strips, or hardwired appliances are hidden behind cabinets. Try connecting a GFCI circuit breaker to each circuit to find faults.
 
ramsy said:
Roger that, and removing loads may be impractical when power strips, or hardwired appliances are hidden behind cabinets. Try connecting a GFCI circuit breaker to each circuit to find faults.
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Connecting a GFCI breaker will be of no use unless you also connect the neutral exclusively to the GFCI.
At that point I would just ohm out the circuit with the neutral lifted instead.

mobile
 
OP needs a fault test, not just a OHM continuity test.

Properly connected GFCI breaker, or
Megger test to ground with all lifted.
 
ramsy said:
OP needs a fault test, not just a OHM continuity test.

Properly connected GFCI breaker, or
Megger test to ground with all lifted.
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Is the OP using a multi meter? I assumed he was using a megohm meter.

I don't trust multi meter ohm readings for much other then testing fuses or dead short to grounds. To me it's like troubleshooting with a non contact voltage detector. They will eventually make a lier out of you.
 
redarchflash said:
I have a commercial occupancy where I'm required to do a neutral fault test my test is showing up with 193 ohms that I cannot get to drop at any point any suggestions on what would be causing this. I have already run through the entire building and made sure that the neutrals and grounds are separated. 3phase 4 wire 208/120 volt 1200 amp.
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send me a PM. i've ran into this test in huntington beach a lot,
and have some experience in resolving it.
 
Smart $ said:
Yes, it should be done with a megohmmeter. if looking for GFCI-tripping faults. However, a typical ohmmeter will find bolted and low-resistance faults.
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And if chasing a low resistance fault and trying to close in on it via ohm readings at various places, a low ohm meter (which is sometimes an added feature on a megger) is really what you want. You need to find small differences between two low resistances.

If you do not read continuity with a multimeter, then, as noted, it does not prove that there will be no leakage when line voltage is present. For that you do need a megger on a high source voltage range. But the OP is already seeing a low resistance.
 
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