Strange Electrical Problem

[Ajax]

He was using a handsaw that the plumbers use to cut PVC. It has a plastic handle that would have provided some protection. But there were no arc burns on the blade. Strange.

The circuit was never under any significant load. At the time it first tripped the only load were two alarm clocks. The greatest load that it ever received was from the motors on an adjustable bed.

The arcing was between, as best as we could determine, a hot leg and ground. This was a four wire conductor - two hot, one neutral and one ground. There is a possibility that neutral was involved too as some of the insulation was damaged but we didn't see any arc burns on the neutral conductor.

[Chris Lewis]

According to Ajax :

Glad you found it. The issue here was that conditions were such that slight moisture/movement variation provided intermittent conductivity (or arc) between the nicked conductors, and at other times, there wasn't enough carbon path to show up on the instruments.

Heh. The last time I did a full house rewire (actually a major duplex rewire, two systems), every time I came over for a wiring stint, the plumber had managed to do something awful to the wiring I installed the previous time. Like the time his 3" drill caught a wire, and pulled a _whole_ circuit, boxes and all, out of the wall.

At one point, about 50% of each day was spent fixing what the plumber wrecked from the last time.

[He really was a damn good plumber. It was a huge and difficult job. He apologized, I eventually forgave him ;-)]

[Ajax]

It was intermittent to the degree that it passed a test by an Ideal(TM) circuit analyzer. If any of the conductors were shorted or open at the time the Ideal tester would have found it.

This meter also measures ground to hot current and it was showing a very low reading, something like .12 volts. Anything under 2 volts is considered to be within the normal range. After the cable was repaired the ground to hot voltage went to zero.

Aparently there was some leakage between ground and hot all of the time, but it was not enough to cause the breaker to trip most of the time.

I have always though that the electrician should be the last trade on the job. Plumbers can do a lot of damage that often is not obvious until someone finds a dead circuit or worse.

[Jim Redelfs]

Second that.

However, it's the low-voltage stuff, like phone, that is PARTICULARLY vulnerable to damage by subsequent persons working around it.

Telephone is the "Rodney Dangerfield" of the utility world. It gets NO RESPECT AT ALL from the other trades.

Gas: Boom

Electric: Zap

Water: Gush

Sewer: Ick

Phone: So?

Build a shed and cut the underground phone drop? No sweat.

Don't call the phone company and risk being held responsible, if it was your mistake. You simply splice it back together with wire nuts and thermostat cable, tape it up and put it back in the ground. It will last several months until well after you've cashed the customer's check.

Moving a wall and need to extend the telephone cable? No sweat. Solder a pipe and NUKE the phone cable? No problem.

Don't pay a professional. Just piece it out with a length of thermostat wire and wire nuts and you're done! The customer won't discover the effect of your shoddy work until well after you are long gone. (And it's ALL under sheetrock, baby!)

Yes, Virginia, there IS a special way to make - and repair - phone cable. There has been for almost a hundred years. Call before you dig!