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Unexplained voltage drop in residential circuit
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Posted by tlark (My Page) on Sun, Nov 8, 09 at 4:20
| I’m having a strange electrical problem that I just can’t figure out and I’m about out of ideas. I recently moved into a rented home. In the master bedroom, my clock radio gets reset every time I turn on the closet light. So I started investigating, using a digital volt meter the outlet at the clock radio showed 120 volts. When I turned on the closet light the voltage dropped to about 70v, and slowly came back to about 100v.
The house is 30 years old. I am not an electrician but I know enough to replace a circuit breaker which is what I did for this circuit. The problem remains although the symptoms have improved a little. Instead of dropping to 70v it now drops to about 95v.
There are four outlets in the room which are all on the same circuit. I have an outlet tester and they all tested good. Oddly, the first outlet near the bedroom door does not have the problem I described. But the other three do. The second a load is put on the circuit there is this unusual drop in voltage. I have tested this with different lamps so I know it isn’t the closet light. And I removed all the receptacles and inspected the wiring for looseness or other basic problems.
Any ideas on what would cause this? How concerned should I be? Should I replace all the receptacles even though they seem to be fine?
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Follow-Up Postings:
RE: Unexplained voltage drop in residential circuit
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| Try tightening all the neutrals in the breaker panel then checking all the connections on that circuit. Make sure the receptacles aren't speed wired. |
RE: Unexplained voltage drop in residential circuit
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| Check the connections at the receptacle that DOESN'T have the problem... look for a loose white wire. |
RE: Unexplained voltage drop in residential circuit
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Sounds like aloose connection inthe bedroom. Could be in the good receptacle or one of the bad ones or the light.
Most commonly this is caused by using the backs tab connection. MOve allthe wires to the screw terminals if the back stabs are used. Being a rented house this should be looked by the landlord's electrician. Legally you are not permitted to work on electric in a rented house. |
RE: Unexplained voltage drop in residential circuit
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| you should first find all of the loads on the circuit, by turning off breakers 1 by 1. you'll have a better chance of finding the problem if you know which ones are involved. this is pretty likely a loose neutral in a 3 wire circuit, so you'll also want to know which is the other circuit. i don't consider this a beginners problem, but if you're willing to pay later if you can't figure it out, then go ahead. rick |
RE: Unexplained voltage drop in residential circuit
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| It turns out the problem was with a receptacle in another room. There was one common wall with the master bedroom so the receptacle was on the same circuit. The outlet was well hidden behind a desk, but the second I pulled it out of the wall I knew this was it. One side was badly burned. The wires were so brittle I’m surprised it carried any load at all. It looks like it was burned from the inside out. I would guess they nearly had a house fire. There is no telling what caused it, but I feel better having replaced the breaker. |
RE: Unexplained voltage drop in residential circuit
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| Were the wires on receptacle screws or push-in backstabs? Arcing at a poor connection is unlikely to trip a conventional breaker, as there would never be more than rated current. It is why the newer code versions require arc fault breakers in some locations. |
RE: Unexplained voltage drop in residential circuit
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| The wire connections were made with screws. I took a photo for the landlord and uploaded it to the following link in case you are interested.
http://www.thelemonclub.com/forums/showthread.php?t=11307 |
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