An opinion poll--- Some times a customer loses a portion of a ckt. due to an open connection somewhere. It can be tedious enough tracing it to a poorly connected device. However, in the past few months, I have had broken circuits in what must be buried JBs("the carpenter did the electric"). In one case of a broken hot, I used the neutral to ID the circuit at the panel. After removing the hot from the breaker, and attaching an note, I re-fed the circuit at a convenient point. If the bad connection was in the middle of a circuit, the first few outlets would not work, but everything came up. If, for some reason the bad connection "re-attaches" itself, the disconnected hot at the panel will become hot, but I didn't know what else to do. A few months later someone else called with the same problem, but before I could get there, someone else came out. The customer told me that "after taking a bunch of outlets apart, He couldn't find anything, so he had to run a new wire".
Redsy; Thats an ingenious idea to back feed the circuit and look for the open. When the open is intermittant like that and the panel checks out ie breaker is ok and the neutral is ok, then the only other thing to do is to open every box and check the devices, I have found since the advent of back-fed devices that a lot of new homes are made up that way. There is only a point contact when a receptacle is wired by back-feed and with heat and use the spring tension becomes lose and an open can occur easily and re-weld itself back together. Out of desparation I will take a rubber mallet and tap next to all the offending receptacles and someitmes you can find the offender. The good news is that 95 % of those problems are indeed in a box but if you have a burried JB then thats a problem. You say the carpenter did it, i wish that was always the case. Had one addition that the Ahmish built and they wired it too, talk about a nightmare I wound up rewiring the whole addition, but thats another story.
I used a similar method to the one suggested by Bordew.
I used to do a lot of service calls to mobile homes wired with aluminum. Usual complaint was that 1/2 the stuff didn't work. I'd turn on every light switch & table lamp & then beat on the walls with my fist (rude & crude, I know) & when the lights flickered, went to the nearest box & tightened the connection.
This method really does work, but the customer really expects to see something more high tech than a fist or rubber mallet.
Few things are harder to put up with than the annoyance of a good example.
You want high-tech? Maybe its just my background as an electronics tech, but I have used a dual-trace portable oscilloscope (Fluke ScopeMeter) to track down elusive intermittents.
By connecting between neutral and the 2 hot phases at the panel, and watching the relative amplitude of the 2 phases, one can determine whether the problem is a loose neutral at the service drop (one phase goes high, one goes low), a loose backwired receptacle connection (affected phase increases slightly as connection arcs-other phase unaffected), or a bad connection in the meter socket/disco/main breaker (one phase drops, other phase unaffected). By connecting the scope to the branch breakers, bad breakers and burned panel busbars can be found. A current probe is a neat accessory, but not a must-have. To help find the fault, turn on all the lights you can, and plug heavy loads into a few affected receptacles (I use a couple of 1000W halogen photographic lamps).
A combination of the scope AND a helper with a rubber mallet (looks better than a fist ) can help track down those nasty intermittents.
A suitable scope can be found nowadays for a few hundred dollars. Wide bandwidth is not needed, but complete line isolation (battery power) is essential for safety. 10:1 probes (rated for line voltage) are a good idea.
A scope and current probe is also nice for troubleshooting neutral overheating/harmonic current problems, or looking for radio interference from cheap dimmers/X10 modules/photocells/etc.
[This message has been edited by NJwirenut (edited 10-17-2001).]