I have a home run coming into my master bedroom. When I checked the voltage it showed 85v instead of 120 and the I checked a power wire in the same box feeding a plug and it showed 15v and when I checked their voltage together it showed 98v. Could there be a small nail through those two wired at some point?

  • Are you sure you are measuring the voltage between hot and neutral? Are you using a contact meter? Non-contact meters can be notoriously misleading. – A. I. Breveleri Jul 13 '16 at 19:07
  • You should also check for a voltage difference between neutral and ground. This would indicate a broken neutral connection. – A. I. Breveleri Jul 13 '16 at 19:09
  • Yes -- what's the N-G voltage in your master bedroom? – ThreePhaseEel Jul 13 '16 at 22:30
  • I would also check the hot to ground if it is 120 or close the neutral is broken someplace or a outlet prior loose in a back stabb. Unless this is the first outlet in the run. – Ed Beal Jul 13 '16 at 23:37
  • Something as simple as a loose wire nut could be the problem – Kris Mar 25 '17 at 16:09

Any time I measure an undervoltage like that I immediately suspect a broken or floating neutral wire. This is potentially hazardous because it means other outlets and devices in the same house may be seeing an overvoltage.

If you are confident that you have measured those voltages accurately, then all the electrical service in your house may be dangerous. The safest thing to do is turn off the main circuit breaker and call a licensed electrician.

  • Over voltage for a broken neutral ? Where are you from ? the only way that could happen would be on a wild leg delta. I don't think this has ever been legal in a home in the U.S. – Ed Beal Jul 13 '16 at 23:31
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    See e.g. the fourth case in this answer diy.stackexchange.com/a/12552/45091 - what happens when we have an open neutral, and an unbalanced load? – A. I. Breveleri Jul 13 '16 at 23:42
  • I have been doing this kind of work for many years and have a degree, it is easy to make a high impedance example when house hold wiring is very low impeadance. – Ed Beal Jul 13 '16 at 23:49
  • Well you are an electrician and I am not, so I must advise our audience to defer to your opinion over mine. But I remain convinced that if the neutral bar in the service panel becomes disconnected from the power company, and the outlets and loads on one phase are seeing 85 volts, the outlets and loads on the other phase will see 155 volts. – A. I. Breveleri Jul 14 '16 at 2:52
  • I would agree with a neutral from the feeder having funny voltages but not from a 120 home run. – Ed Beal Jul 14 '16 at 3:26

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