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You are here: Experts > Home/Garden > Home Improvement/Repair > Electrical Wiring in the Home > Short cirucit?
Expert: Greg Hughes - 10/30/2009
Question
House electrical to separate building (Studio). Problem: Low voltage 20-30V on the studio side.
On the house side I have 110 volts on the circuit breaker, double 100A breaker. to the studio on 2 separate legs (used to have a 220v washing machine in the studio which has long ago been disconnected. Now in the studio are 2 x 20amp breakers which feed a couple of florescent lamps and 5 wall outlets. In the studio I have only 20 or 25V volts coming in when checked with a meter. The house breaker to the studio is a old cutler hammer breaker (which was made in the U.S. and the replacement now made elsewhere). I replaced the house breaker but still have the same problem. If I detach the breakers in the studio I have 100 Volts. Then if I attach or energize either breaker it drops down to 20 or 30Volts.
Last month I dug a trench around my house because of water problems. I'm wondering if I may have nicked the cable going to the studio which is why it can't carry the load. Though the problem just now showed up, we have also just now had a lot of rain.
Can I confirm this by checking continuity between the hot and ground/neutral? (with both the main breaker off, and studio breaker unplugged as well...checking for continuity from the main house studio unplugged breaker and ground?#
Or may the fault be within the studio building. #I thought not as I can energize either of the two circuits and get a drop in voltage.)
Answer
You say you have 110 volts at a double pole breaker but you should be getting 220 volts across them.
So do you have 220 volts across them and 110 volts from each one to neutral?
When you install the breakers in the studio is there any load? If you do not connect any wires to the breakers do you still get the voltage drop?
If you do have a nick you may or may not get a reading to ground (continuity). Let's say that the nick is not in direct contact with a ground and when you apply voltage it jumps across to the ground, if this is the case you will not get any readings of a short.
I have seen this happen in mobile home when someone put a nail in the wiring. It was not touching the hot but was close enough to jump across when voltage was applied.
Also, if you partially cut the wire and it is not grounding but having to jump across to the wires or it simply cannot jump across you have created a voltage drop. It would be equivalent of installing a smaller piece of wire.
If you did break through the conduit you will need to dig it up and fix it. If it is underground wire with no conduit you will still need to dig it up and fix it. Or, you can simply run new wire, but if the conduit is broken you will need to get the water out of the pipe and fix it.
Hope this helps.
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