Current on ground

[Twoskinsoneman]

I've been trying to solidify my knowledge on unbalanced circuit to be able to explain it a little better to the guys that work at our shop. Anyway on a job where the rough in is done and there are only two circuits powered (window AC unit and radio/drop lights) I decided to check the amperage draws. None of the other circuits have receptacles, just wires pushed into the boxes. They are terminated at the sub panel. Anyway I couldn't figure why I had 5.5a on one leg .5a on the other leg and only 4a on the neutral. Scratching my head I tried the EGC and found the amp there. Is it normal during construction to have this happen? I figure at some outlet somewhere the neutral is touching a ground. Is this what you suspect also?

 

[mdshunk]

Where did you take your measurements? If you measured the service neutral at 4 amps, and the grounding electrode conductor at 1 amp, I might call that semi-normal considering the resolution of the meter you were probably using. Particularly if you have a good metallic municipal water line ground.

 

[Twoskinsoneman]

Where did you take your measurements? If you measured the service neutral at 4 amps, and the grounding electrode conductor at 1 amp, I might call that semi-normal considering the resolution of the meter you were probably using. Particularly if you have a good metallic municipal water line ground.

It was at a sub panel. The construction is an addition, a detached garage. Should have none right?

 

[mdshunk]

It was at a sub panel.

Ah... missed the subpanel part. My suspicion normally goes to the hermetic compressor in the air conditioning unit. As the windings age in refrigeration compressors, they develop low-level continuity between the windings and the grounded hermetic can. Just a guess. Ideas for your consideration.

 

[jetlag]

Idea

Idea

I've been trying to solidify my knowledge on unbalanced circuit to be able to explain it a little better to the guys that work at our shop. Anyway on a job where the rough in is done and there are only two circuits powered (window AC unit and radio/drop lights) I decided to check the amperage draws. None of the other circuits have receptacles, just wires pushed into the boxes. They are terminated at the sub panel. Anyway I couldn't figure why I had 5.5a on one leg .5a on the other leg and only 4a on the neutral. Scratching my head I tried the EGC and found the amp there. Is it normal during construction to have this happen? I figure at some outlet somewhere the neutral is touching a ground. Is this what you suspect also?

To check marks theory , try unplug a c and run power saw on a c plug , I assume its 120 v . If EGC goes to zero, A C is getting old. I assume you didnt connect bonding Jumper in sub panel because EGC and neutral would prob show 2.5 a each.

 

[al hildenbrand]

To eliminate the AC EGC in the branch circuit in contact with the grounded conductor along the branch circuit route as the cause, lift the branch circuit grounded conductor (neutral), unplug the AC and lights/radio and look for continuity or low resistance between the EGC and the floating neutral.

The EGC - neutral connection should read a very high (megaohms) resistance.

 

[Twoskinsoneman]

Found the cause.

When the panel was being terminated the tech couldn't find where one circuit went. For some reason he stripped the neutral to do a continuity test at an outlet. After he found the circuit in the subpanel he just pushed the wires back into the outlet box and of course the neutral was pushed up against the bare EGC.

Thanks for eveyone's input.