I have a friend who called me over to check his garage voltage out. He had some 120 volt outlets not working. He has a 120/240 feeder coming from his house feeding underground to a garage about 75ft. away. I check the voltage and find out that there's one phase not getting the right voltage. I was getting 123 volts to ground on one phase, and around 74 volts on the other phase. At first I thought one of the conductors were broken or burned under ground, then I traced it down to a HID fixture mounted on the outside of his garage. When I turned this breaker off, the voltage came back to 245 volts between phases. I then hooked up everything the way it was before ( I had to change the piece of rusted conduit that was coming up into the panel. After I hooked it all back up, I checked the voltage again. It corrected the voltage almost, but I'm still getting 123 volts on one phase and only about 111 volts on the other phase. Still seems to be something not exactly right.First question is how would a bad ballast in the light make the power to fluctate on the main lugs like this? 2nd question: Do you think there still might be a "bad wire" under ground causing the difference in voltage on the two phases? Thanks for the input.. Steve
Since the neutral path back to the main panel is broken, you aren't drawing current from a hot wire and neutral. You are drawing current from the hot wire and all of the appliances, lights, stereos, etc on the other hot wire.
When the load is balanced perfectly between the two legs, the voltage will be balanced. Any imbalance in load will cause an imbalance in voltage.
I would check the neutral out, it's connection, and also the connections of the grounding electrode. I've seen a corroded attachment to a grounding rod cause some odd things, like getting 75 volts from the water running out of a faucet to a stainless steel sink or a guy's wife getting a shock by the water in her washer.
111 volts on one leg is indicative of the failure being on that particular hot leg, not the neutral. It should be easy to determine by removing all loads and measuring between each leg to the neutral (NOT the ground).
Thanks for the replies. I haven't got a chance yet to go back and check the voltage again. It only has a 3 wire feeder to the panel in the garage. There was some digging in the near proximity of it a few months ago( 3 feet or so), but the owner hasn't said anything about any problems til now. I guess it's possible a wire got nicked somewhere, and is just now deteriorating to the point of causing a problem. We will just have to dig in the general area and see if that's the problem. I originally told him, it looked like a wire was broken underground, so we may still have that problem. Thanks again... Steve
You could disconnect the wire at both ends and loop a load through them in different combinations checking voltage drop across the link. Use something hefty like a space heater so the voltage drop was apparent.