155v?

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  #1  
Old 11-30-10, 01:59 PM
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155v?

Short version:
Why would I be seeing 155V on my 120 circuit?

Long version:
I had to move my hall light to frame in an attic staircase. The supply comes into the box (paper wrapped 12-2) and is wrapped and glued to 14-2 NM that runs to a switch to control the lamp and 14-2 NM that continues on and supplies power to receptacles and lights in other rooms. Originally there was a fan in the hallway, but it died and I replaced it with a new light fixture.

I moved it by cutting all three cables at the box (preserving the inside of the box so I could re-wire like it was before), and then installed a new box, then stripped and nutted the wire exactly like it was before. I went to test the circuit later and (after tripping the breaker and almost blowing up my multimeter because I had the wrong test lead on it) measure 155VAC. All the lights and outlets work. Is this normal?

FYI: the house was built in 1948, and it looks like at least three re-wires were done.
 
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Old 11-30-10, 02:19 PM
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Do other receptacles also read 155 volts? If so take your meter to a friend's house who lives at least several blocks if not miles away and check the meter on their receptacle. If it now reads about 120v you know the meter is good. Check other receptacles at your house if all read 155v call the power company emergency number and tell them you may have too high voltage. I would use no electronics till this is resolved.
 
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Old 11-30-10, 03:48 PM
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I'll check on that tonight. If it is just this circuit, what could be the problem?
 
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Old 11-30-10, 04:01 PM
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It is not necessarily a DIY project.....but the cause may be related to a neutral open....This could be on just one 3 wire circuit, or the whole house. It can result in things seeing 240 that should only see 120, and it can give you funny readings like your 155. But it may be serious, so don't let this problem twiddle along.
 
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Old 11-30-10, 06:27 PM
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The dead giveaway of a problem with a neutral would be if you also found receptacles in your house which measured roughly 85V. (155V + 80V = 240V) If you took this measurement at the lugs in the main panel it would imply the problem is with the service entrance or the power company.

Odd voltage readings can also be caused by weak batteries in the multimeter or phantom voltage on an open circuit.
 
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Old 12-01-10, 02:42 AM
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Originally Posted by ibpooks View Post
The dead giveaway of a problem with a neutral would be if you also found receptacles in your house which measured roughly 85V. (155V + 80V = 240V) If you took this measurement at the lugs in the main panel it would imply the problem is with the service entrance or the power company.

Odd voltage readings can also be caused by weak batteries in the multimeter or phantom voltage on an open circuit.

Ben is right on the last part weak battery is useally most common curpit and phantom voltage will show up but not that high unless you snag into 240 volt circuit.

If you only have DVM ask your freind to borrow their unit to make sure you are getting correct voltage and do the light bulb look super bright or dim if that the case you have leigt loose netural either on MWBC { multi wire branch circuit } or loose netural either at load center or meter socket or POCO connections but first go with basic real quick with light bulb { Not the CFL type just the regular type so you can indentify quick }

and let us know

Merci.
Marc
 
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Old 12-02-10, 07:24 AM
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I used a rather un-scientific measure of battery performance (it was a 9V) and determined that my battery was about dead. I'll re-measure today after getting a fresh battery.
 
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Old 12-02-10, 08:23 PM
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You guys were right on: dead battery. I got a new one and it works great now. Oh, and I'm getting 120V!
 
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Old 12-02-10, 09:34 PM
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Thanks for letting us know. Guess you can add that to the list of reasons to use an analog meter.
 
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