Partial power failure

[RBM]

A customer called with an intermittent electrical problem: The electric range and refrigerator on occasion stop working, then start working for no apparent reason. It's obvious that one of the hot legs is opening, as that would be the only common denominator between a 120 volt refrigerator circuit, and a 240 volt range circuit. The customer was also unaware of a multitude of other circuits that were also dead. Usually when I get these calls, I start with the connections in the most hostile environment, 1) The overhead service connections, 2) The outdoor meter socket, then check the main circuit breaker. In this case the culprit was the main circuit breaker, which by all outward appearance, looks fine. There was antiox paste on the conductor connections, no hissing or crackling sounds, and the breaker was cool to the touch. Upon removing the breaker, the problem became clear. A bad connection (factory) between one pole of the breaker and the panel buss, over time caused overheating and annealing of both the panel buss and the copper contact of the breaker. Pictures to follow:

[John Grabowski]

Thanks for posting Roy. Did you have to change the load center?

[RBM]

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Yes, that one section of buss was shot. My picture doesn't show how discolored it is was where the breaker connected to it. This is the 3rd Murray main breaker go bad this way that I've seen in this past year. The other two showed up in time to save the buss.

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[Pete C.]

Eeew! This is why I stick with Square D QO equipment. Even then I do inspect items as I'm assembling and installing them.

[Joe]

Well that's one for the books. Nice pics, too.

Joe

[Stormin Mormon]

A couple friends of mine were having power problems in their home. Their panel box was modern, can't remember what brand. Anyhow, the mains power came in through a double 100 breaker. There was a lot of white oxidation where the breaker connected to the panel. Myself, and the resident used strap on head lamps, to see. Turn off the main breaker, and unsnap it from the panel. Tough to do, it was plenty corroded on. Clean the distribution bars with sand screen. Pump a bunch of anti oxidant into the open slot end of the breaker, and put it all back together. No further problems.

Those are very good picture. Thanks for posting. The repair I did, was before I got my digicam.

[Stormin Mormon]

That does look like an older design.

[Stormin Mormon]

Third this year? You are an electrician?

[RBM]

As long as you catch it before the buss metal is destroyed from overheating that'll work. These Murray panels have bolt on main breakers, installed at the factory. There was some antiox on the connection, so my guess is that it's just a poor design. Murray no longer uses this type of main breaker.

[Stormin Mormon]

Must have caught this one, in time. Worked till they day they moved. Which was a couple months later.

Did you shut off the mains, by pulling the meter or something?

[RBM]

I have two electric companies in my area. One installs case hardened locks on the meter boxes, the other just uses a wire tag. With the locks, I have to cut the overhead conductors, then rebug them when I'm finished. This one was a tag type, so I just pulled the meter

[Stormin Mormon]

Yes, that does sound safer than working on live circuit box. The power co in my area uses Highfield barrel locks. Some of the meters have the metal tag with the serial number on it. They are pretty good about coming out to pull meters as needed, if an electrician is working.

Cut the overhead feed wires sounds do-able if you have the right insulated cutters, and have whatever butt connector crimps are needed to put the wires together. I'm not sure I've got the courage or confidence to be cutting high amp wires like that.