Hunting the Short

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  #1  
Old 08-29-01, 05:10 AM
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I have an older home (built c. 1930) that originally had knob and tube wiring but has been "re-wired" at least a few times (I have an open basement, so I can see the evolution of the wiring). Unfortunately, at least one of the folks who wired this wasn't too bright and now it's coming back to haunt me (I think).

So here's the situation. There is one circuit that seems to power the receptacles in my living and dining rooms, as well as the garage. But this circuit is not wired into the junction box. Rather, there is another, newer, line that is wired into the junction box and then goes to one of my plugs and from there (I am guessing) it powers the rest of the circuit. I discovered this this summer when I was finishing off a part of the basement, and decided not to touch it because it seemed to work and if it isn't broken, why fix it, I thought.

Well, now it seems to be broken. Just this weekend, I lost power and keep blowing the breaker (15 amp). Two things happened: I had my kitchen floor sanded (using the 220 volt circuit for my dryer) and we had a thunderstorm. Something has caused a short circuit--does anyone have any suggestions for hunting down the short circuit, short of rewiring the whole sucker?
 
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Old 08-29-01, 07:59 AM
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Fixed the short (sort of)

Just to update--I no longer have a short and have power back to my dining and living rooms, but now I have no power to my garage.

So a question: the line to the garage runs through a corrugated steel cover. How hard would it be to pull new wire through that. All things being equal, I probably wouldn't mind just re-wiring that on a new circuit.

Any suggestions?
 
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Old 08-29-01, 08:34 AM
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Q?-you say "circuit not wired into junction box"-by "junction box" do you mean the circuit-braker panel?---to clear the fault remove the wire from the circuit-breaker and wire-nut the wire to one lead of a lamp socket and connect the other socket lead to the CB terminal.Put a 200 watt lamp in the socket and switch the CB ON.If you have a "bright lite" you need to clear the fault so the 200 watt lamp goes out or appears dim.Put all switches (if any) in the defective circuit OFF and remove the lamps from all fixtures.Next is to open the "Black" connections at each outlet one-at-a-time,checking the test lamp after each connection is opened and look for exterior or "outside" outlets.If you open a Black connection and the test lamp at the panel goes out,re-connect the wire to the CB and switch the CB ON.With the test socket test each Black to the Whites to find the "live" Black.Test between the "live" Black and the other Blacks with the 200 watt test-lamp to find the defective Black.Note which outlets are still dead, then check those outlets.The possible presence of K&T wiring complicates the problem-Good Luck!
 
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Old 08-29-01, 10:00 AM
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I don't know what a corrugated steel cover is exactly, but I like the idea of running a new line to the garage on its own breaker. To see if the existing garage feeder has the short, determine where it connects to the LR/DR portion of that circuit, like maybe the last interior receptacle inside the house, and disconnect the wires to the garage from that point. Turn the circuit breaker back on and the LR/DR should still be working fine. Now get a continuity tester and test across the (now dead) hot and neutral going to the garage, then the test across the hot and ground. You should see continuity across one of those pairs if there's a short. It sounds like you have an "open" circuit though. The garage doesn't work because the hot is not getting through.

One thing that may cause this is if you have a loose connection in a LR/DR receptacle which feeds receptacles downstream, including the garage. And I would suspect that it is back-wired with push-in style connectors instead of the side screw terminals. These connections are notoriously lame and cause dropouts all the time, but usually not shorts. A surge like lightning hitting the utility and passing down to the houses in the area may be enough to weaken the internal connections of the push-in terminals. The panel feeds the first receptacle of a string of receptacles, then that receptacle feeds the next, and the next one feeds the next...and so on. If a loose connection occurs in one receptacle, the upstream ones work and the downstream ones do not, which can be frustrating to find since SOME of the circuit works. To find the faulty receptacle I would grab a plug-in device like a light, or even one of those 3-to-2 prong adapters 'cause all you need is the plug to do this. I run around to all the receptacles and wiggle them firmly. If other receptacles go on & off or flicker, the loose connection is usually in the one you're wiggling at the moment. Kill the breaker and pull that receptacle out and check. If it was wires with push-in connectors replace it, using only screw terminals. (Black goes to the brass screw, white to the silver screw.) When testing this way I usually plug a radio into any receptacle on that circuit so I can hear it go on & off as I wiggle each of the other receptacles on that circuit. Since you lost the entire circuit and then the LR/DR came back it is quite likely that plugging and un-plugging things in the mean time wiggled a loose connection and caused part of the circuit to come back on line.

Another thing that could cause this is a tripped GFCI somewhere on that circuit. It's often one in the mosr illogical place that's causing the trouble. Resetting the tripped GFCI may bring the garage back on.

Hope that helps.

Juice
 
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