58 Volts on one Leg of service wire

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Cklein

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Midlothian VA USA
In the main panel there is a 100 amp breaker providing power to the detached garage. #2 wire feeds the garage. (Hot, hot, neutral, ground) 100amp panel in the garage.

At the garage, we are getting 120 on one leg and 58volts on the other.

At the main panel at the house, we are reading 120 on each leg. No load on our neutral or ground. So, everything appears to be correct at the beginning of the circuit.

Could the wire be damaged somewhere between the house and garage? Would a damaged wire cause half voltage on one leg?

Things we have checked....voltages everywhere. The only bad reading is at the garage on the one leg. Neutral and ground connections look good. We even swapped the hots on the 100 amp breaker at the main panel to see if the 58 volts swapped legs. The 58 volts stayed on the same wire with no change to the 58 volts.

Any suggestions?
Thanks,
CK
 
Sounds like an open in that conductor, and you're reading half voltage with a high-impedance voltmeter. Does that voltage collapse to zero with a load on that hot line, or does it remain?

You need to check voltages with a load on and check at every accessible point. Odds are the issue is at a junction, but could be underground. What is the underground wiring method?
 
Like Larry said and I have seen it many times, if an underground hot leg goes bad, you might read some voltage with a high impedance meter, but even the smallest loads will drop it to almost no voltage at all. Still enough continuity through the bad point to get such a reading, but resistance is too high to let much current at all through, so nearly all the voltage drop is across the bad point when you add a load.
 
LarryFine said:
Odds are the issue is at a junction, but could be underground. What is the underground wiring method?
Click to expand...

I certainly would look for a bad junction but if I didn't find one I would question the owners about where they or contractors have been digging.

I remember a stump grinding incident a few years back, turns out the cable wasn't buried all that deep.
 
growler said:
I certainly would look for a bad junction but if I didn't find one I would question the owners about where they or contractors have been digging.

I remember a stump grinding incident a few years back, turns out the cable wasn't buried all that deep.
Click to expand...

Abuse during installation or even shovel nicks that didn't get repaired if it were ever exposed at some time is a great place for (especially aluminum) conductors to fail over time. Underground varmints also tend to cause problems at times.
 
Larry,
We just checked voltage with a load and yes, the voltage collapsed to zero. There are no junctions between the interior panel at the house and the subpanel at the garage. The wire runs through the crawlspace into conduit as it passes underneath a patio and is direct bury the remaining way to the garage. 24 inch deep.

Are you thinking that the one hot wire is damaged somewhere in that run? I can’t think of any other possibility….

LarryFine said:
Sounds like an open in that conductor, and you're reading half voltage with a high-impedance voltmeter. Does that voltage collapse to zero with a load on that hot line, or does it remain?

You need to check voltages with a load on and check at every accessible point. Odds are the issue is at a junction, but could be underground. What is the underground wiring method?
Click to expand...
 
Cklein said:
Are you thinking that the one hot wire is damaged somewhere in that run? I can’t think of any other possibility….
Click to expand...
I am. If direct bury means no conduit, replacement is difficult, to put it mildly.

If you have little load and no L-L load, you could convert it to a 120v feeder.
 
Besoeker3 said:
Between which conductors are you measuring these voltages?
Have you tried measuring L1 to L2?
Click to expand...

So that is the plan for now. L1 is functioning fine thus we can have a 120v circuit for now. It is going to take some effort to get back up and running with 240. Fortunately we have conduit under the hardscape.

To answer the the other question, we have 178 between L1 and L2 at the detached garage.

Thanks to you all for bouncing around thoughts.

Chris
 
Cklein said:
So that is the plan for now. L1 is functioning fine thus we can have a 120v circuit for now. It is going to take some effort to get back up and running with 240. Fortunately we have conduit under the hardscape.

To answer the the other question, we have 178 between L1 and L2 at the detached garage.

Thanks to you all for bouncing around thoughts.

Chris
Click to expand...
That 178 volts should also pretty much disappear with a 240 volt load applied across it, and leave both lines at a nominal 120 to neutral/ground, if they are good.
 
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