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electrical trouble shooting

tcleveen's picture

I have three sequential wall plugs that I put in in a room that are now not working (they showed OK power before the sheetrocking occurred). Three othe plugs in the room (on other walls) wired at the same time are working. The three that aren't showing power are fed by two of the ones that are working ie. they are on one circuit and as I test each plug in the room (wire feeds each successive plug on one circuit) I finally get to a wall where the first non working plug is and the remaining two plugs "downstream" aren't working either. So I know that circuit has power but It doesn't stay live as I go around the room. Wire connections in the plug boxes look OK. Could a sheetrock screw have caused this problem in covering up the walls? If so, wouldn't there be short somewhere? What test is there for determining exactly where behind the wall board this problem is originating; I don't want to have to start cutting into new walls to diagnose the problem. Is there a piece of testing equipment perhaps sold at electrical supply houses that could scan the walls and look for screws penetrating romex? How do I pinpoint the cause of no power without trashing the newly installed wallsboard? Thanks in advance for any advice.

You can use one of the (post #195656, reply #1 of 3)

You can use one of the Christmas tree thingies to scan the DW screws and see if any register "hot".  But this will only work if the screw hit the hot wire, and if the screw is still in contact with the "live" side -- about a 25% chance overall.

You can also use a time domain reflectometer to find out how far away the break is.  Near certain success, but those ain't cheap.

Not that it matters much.  The entire cable will have to be replaced.

(Did you make sure that all the wires were at least 1.5" back from the surface of the stud?  Or put a nail plate over any that weren't?  And use screws with LESS than 1.5" penetration?)


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

If you know how the wire run (post #195656, reply #2 of 3)

If you know how the wire run goes and are sure that the drywall installation caused the problem "just" rerun the wire between the receptacle that works and the next one in the series. OTOH if you can locate the actual problem and you have enough slack or you replace the wiring on one side of the problem you might be able to install a junction box or receptacle to make a new connection. PITA either way, good luck!

I would check the connections (post #195656, reply #3 of 3)

I would check the connections of the 3rd receptacle in the string that IS working (inside the wall box) that leads to the first of 3 not working.  Perhaps the connection came loose while installing the receptacle...then I'd fire the electrician for having loose connections.