[NA]Mains voltage differential

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
To the grounding pin, there is 115v on one hot and 125v on the other.
I am used to seeing much closer readings.
Within normal?
Call the utility?
Going to use a (220v) TIG welder soon
 
Let'sgoflying! said:
To the grounding pin, there is 115v on one hot and 125v on the other.
I am used to seeing much closer readings.
Within normal?
Call the utility?
Going to use a (220v) TIG welder soon
Click to expand...
Try turning off all your tied breakers to 220v appliances. Something might be leaking to ground.
 
You should get an identical voltage when checking the two hots against the ground as you do the neutral. If you don't, you have a problem.

As far as the two hot sides being different, it could be harmless. The normal range is 114 to 127 in the US at the service entrance. So it's within spec. A difference between the sides could just be load on the two halves of the utility transformer being different, especially if the transformer is feeding multiple houses or apartments. Or, it could be a poor connection in the neutral or one of the hot wires from the panel to the transformer. One way to maybe check that is to turn off all the load, then check the voltage difference as you add load. If it doesn't get any worse than you have, it's most likely fine, in my "guy on the Internet" estimation. If it swings up to a voltage on one side > about 130-135, then I think you have a problem with your neutral. If, on the other hand, when you turn off all the load both sides go up to 125-127, and one side drops with load, you may have a poor connection on that hot side, from panel to transformer. Of those two options, a problem with the neutral is more dangerous. Not because of shock danger, but because if your neutral opens you can see up to 240v on a 120v circuit, and that can cause many 120v to fail.

Short version? As long as neither side goes below 114 or above 127, it's probably fine. If either side swings below 110, except in a brownout, or above 130, you may have a problem.

As far as the welder goes, it's only looking at 240v across the hot leads, it'll be fine.
 
This is with the load (hangar) physically separated from the distribution panel. Ie the main breaker's wires disconnected from it.
 
It doesn't even have to leak to ground. We're not talking current here but voltage. A different amount of load on one side of a 240 feed will result in a different voltage drop.
 
If you have a neighbor on the same transformer, it might help to measure his voltages and compare to yours. Or, for that matter, have your voltages EVER measured the same?

Tim
 
Lindberg said:
Try turning off all your tied breakers to 220v appliances. Something might be leaking to ground.
Click to expand...
Maybe throwing all breakers in the panel then check again. If they are now the same, start throwing 110/120 breakers on one at a time and check to see if you can find which circuit might be leaking. Not necessarily leaking, it could just be something plugged into that circuit with a high draw. If none, then throw other 220/240's in the panel and check. Or maybe just throw everything off first and check each of the 110/120 drops from the Electric Company. Maybe it's nothing in your house doing it.
 
Un balanced load on your equipment or ANY of the other tenants of the hangars will give unbalanced voltage everywhere.

As Albany Tom said, you are well within industry standards, and your welder should work to its capacity.

Not just any internet opinion, I worked in the generation and distribution division of a major electric utility.
 
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