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Dead Household Dircuit





Dennise
... not sure this belongs here, but I couldn't locate a better FriHost forum.

Does anyone have suggestions for troubleshooting a dead household 120 VAC electric circuit? A friend wired his new house, but after the walls and ceilings were completed, he has found a dead bedroom circuit. There appears to be no source power for this circuit.

Most signal tracers I have found are actuality intended for locating the circuit breaker associated with a circuit and perform poorly when wiring is concealed behind walls and ceilings. Instead We need to inject some kind of signal into the dead circuit and trace associated wiring that is inside walls and ceilings. The house is not occupied so we have the flexibility of turning any circuit breaker on or off at will.

Any ideas on how to determine where this dead circuit goes?
weableandbob
I can't think of much besides checking your circuit breaker connections. If something has happened to the wire itself inside the wall, there isn't much you can do to check where the circuit is broken.
jwellsy
I know utility service locator's can inject a signal into a water pipe that can be detected by a special metal detector.
You could befriend someone from the local water dept to bring out their locator rig. Turn off the main breaker to the house, inject the signal and you should be able to trace through the walls. You could call your local Ace hardware or equipment rental shop and see what they have.
ocalhoun
You don't need any fancy stuff, really.
Just:

- Multimeter, with Ohmmeter/Resistance setting (Cheap ones -- as low as $10 -- are available.)
- One really long wire, preferably with a clip on one end and a test probe (or plug) on the other

1- Check to make sure those sockets aren't wired to a switch - it may be as simple as turning a switch on. Also check the fuses/circuit breakers for blown/tripped breakers and/or any scorch marks. Once done with that, shut off the main breaker, and if possible shut of power from the utility switch outside.
2- Plug the long wire into the dead wall socket.
3- Run the other end of that wire to the circuit breaker panel.
4- Turn on the multimeter, and set it to test resistance.
5- Clip the long wire to one lead of the multimeter.
6- The multimeter should read infinite or very high resistance when not plugged into anything.
7- Touch the multimeter test leads together, the resistance reading should go very low, almost 0. (This tests to make sure the multimeter is working properly.)
8- Open up the guts of the breaker panel - disassemble it.
9- Touch the free test lead from the multimeter to the various wires inside.
WARNING: if you didn't shut the power off from an outside switch, steer clear of the connections for the main breaker; they will still be energized!
10- If the multimeter shows a low resistance reading when touched to any of the wires, then you've found the wire those outlets are connected to. Reassemble the breaker panel, making sure that the connections are all solidly made. If this doesn't fix it, consider replacing that particular breaker. (Also test the other wires in the circuit, there should be two or three, and it's possible for just one wire out of the cable to break.)
11- If the multimeter never shows a low resistance reading, no matter what you connect it to, then the outlets are not connected to the breaker panel. If you can get to any junction box they might go through (often in attics), repeat the test from that point. If you still can't get anything, there's probably a broken wire; new wires would need to be run to those outlets. (Don't panic; this can usually be done without breaking down walls; ask your electrician friend.)
Dennise
Thanks all for your replies.

We found the problem. It was an unconnected outlet receptacle that had been covered over with sheet-rock! Because of that, the wiring inter connections on that receptacle were never made.

We connected a little square-wave generator to a stereo amplifier and then connected the amplifier's output to the 'dead' wiring. Then we used a cheapo AC detector to trace the inside-wall wiring to the covered over hidden receptacle. The amplified square-wave produced a sound in the AC detector that was unique, making the tracing easier. This approach allows detecting the injected signal up to 12" away from the wiring even through the 1/2" wall-board with no fancy expensive special equipment.
FunDa
Dennise wrote:
Thanks all for your replies.

We found the problem. It was an unconnected outlet receptacle that had been covered over with sheet-rock! Because of that, the wiring inter connections on that receptacle were never made.

We connected a little square-wave generator to a stereo amplifier and then connected the amplifier's output to the 'dead' wiring. Then we used a cheapo AC detector to trace the inside-wall wiring to the covered over hidden receptacle. The amplified square-wave produced a sound in the AC detector that was unique, making the tracing easier. This approach allows detecting the injected signal up to 12" away from the wiring even through the 1/2" wall-board with no fancy expensive special equipment.



Wow, that technique is so awesome. I never knew that it is possible to trace a wire like that.

In fact, I have a long long co-axial cable which has lost continuity, but I am not sure where exactly it has broken( the outer insulation is perfect but the inner metal wire has broken somewhere in between. If I can find out where exactly, I can rip out the insulation there and fix it.

Until then, it is just lying around while I debate buying a new cable.
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