electrical wiring


Old 07-07-01, 09:37 AM
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wiring to an exterior light--when switch controlling is in "off" position thre is no voltage across black and white wire--however there is 120v reading from EACH wire to ground--how is this possible--also when switch is on there is only 120 from black wire to white and from black to ground--is this safe?-------------Anthony P.
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Old 07-07-01, 10:32 AM
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Sounds like the neutral is being switched instead of the hotwire. You can confirm this by removing the bulb from the fixture(s) and repeat your test. If you get 120 volts from the black wire to ground and 0 from white to ground the switch is in the neutral leg. If the switch is in the hot leg you should read 0 to ground on both wires. When I say 0 keep in mind that there is always stray capacitive and electromagnetic coupling in a circuit so that you rarely if ever read zero. But it's not 120 volts either.

I don't think this arrangement is kosher according to the Code, but I am not an electrician, just an engineer. It's not especially safe since most people would assume that the hot leg is switched. As long as you don't assume this you're OK. The last house I lived in was wired like this, and I rewired all the switches so the hot leg is opened. I found mine by burning the end off a new screwdriver when I assumed that opening the switch killed the switch loop. I also found that since he was such a good electrician he did the switches wrong, he also left ungrounded all the built in appliances in the house. You might want to check yours too.

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