Broken Ground, Odd meter Readings

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jmellc

Senior Member
Location
Durham, NC
Occupation
Facility Maintenance Tech. Licensed Electrician
Customer called that he'd bought an exercise machine. Tech plugged it into the wall and burned up the display panel. I went out & got a no ground with my Wood head. Measured 120 hot to neutral, 80 some from neutral to ground and 30 some from hot to ground. After checking several receps on the ckt, I checked panel & found a broken ground wire. Missed it several times. The cable came in with several others, all grounds twisted together & wire nutted to a single #10 going to bar. I kept poking around & found this gnd looked part of the bundle, but was broken shortly into the mass of other wires. I terminated it securely & no further problem.

I had been expecting to find a broken neutral somewhere also. Most odd readings I've ever seen were from broken neutral or reversed neutral/ground. No load on ckt when I got those readings.

Anyone seen this before?
 
A broken equipment grounding conductor will not burn up equipment unless there is some other problem. The EGC is not part of the actual circuit.
 
Only when there is a hacked receptacle feeding from somewhere it wasn't supposed to, say a switch loop and the EGC was used as the neutral
 
I've seen things burned up with a lost neutral forcing 240 onto the ckt. But neutral was good here, every recep on ckt had full 120 hot/neu. I checked crawl space & found nothing tapped into ckt.

I'm going back for another job there soon. I'll search further for anything else weird.

I need to set up a small wiring model in my shed & see if I can recreate such problems. I saw a vaguely similar issue in another house with ground picking up current. coming from a mwbc feeding 2 rooms of receps. Could not get to all recepts because of furniture & customer didn't want to pay for more work. Had to let that one go.
 
Ditto on the ground not causing the problem. How many receptacles are wired ahead of this one in the circuit? Are the receptacles "pigtailed" or does the wiring go in one screw and out the other to the next receptacle? Are they wired by winding around the screw or do they use the push in feature? Sounds to me like you have a neutral problem that will only show up under load. A high resistance connection will show full voltage but carry very little current without losing voltage.
 
The "weird" readings were due to phantom voltage.

As noted a broken ground will not damage equipment assuming the circuit is properly installed.
 
Put it back the way it was
Load Hairdryer on the top of the duplex and measure the bottom
Then you know if your n is/ was true w/out the grounding wire
 
I'm going back there for other work soon. I will check out again. I think I opened every recep on the ckt unless something is hidden in attic. HR comes from attic. I found nothing in crawl space.

It bothers me I got N/G volt reading with no load on ckt and got no reading H/G. I do know the owner has done some of his own work before. I wil check attic next time. Maybe something hidden there.
 
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