Saturday, March 20, 2010


Electrical equipment wears out over time

I am amazed at people's ingenuity.

I often answer questions on the FAQ page of my Licensed Philadelphia electrician website, as well as those I receive from DIY and web inquiry sites.

I just fielded the following. The answer was, of course, preceded by all the warnings and disclaimers about being qualified, etc.

Triple socket Main Service. Original problem=Old red colored 125A main breaker (old Murray's?) apparently became loose? @ both bus bars...arced and destroyed both bus bars, one worse than other. I pulled bus bars and cut out bad sections, welded in new aluminum. Old (Murray?) red breaker no longer available. Installed new 125A that fit (New Murray) fits loosely @ opposite side of bus. Everything ok for couple months or so. Soon as Grandma turns on AC, 50A in her sub pops and so does main. I Told her leave breaker in off position until summer and will get it fixed. What do you think is going on???? Obviously there is a short in the compressor circuit. But why is it popping the main at same time. The feed from main to apartment sub is aluminum...Ashamed to admit that during the replacement of said main breaker (in The Rain!)that I did not check to see if Neutral connection was still tight!! I haven't done electrical for over twenty years from when I was a kid. Would a loose neutral at the main act this way? At the time I repaired the bus bars I operated all the stoves burners for 10 min, no main trip. Sincerely,

Right, there is no replacement for the Murray Main!
Pretty nervy remanufacturing the panel bus!
This would absolutely void the UL labeling.

Anyway, it is possible that the material you used to rebuild [rebuild? unbelievable!] the bus wasn't up to the requirements and may have failed again....


You don't sound stumped to me!

The A/C wouldn't need the neutral anyway. Right?
You have observed that there was not really a good mechanical fit in the first place.

The main could trip when the A/C breaker trips if the current is high enough.
Have you checked current levels?

In reality, the fact that you are dealing with the old red Murray breaker tells me that the service has exceeded its economic life. The implant approach was a novel idea [which I cannot professionally recommend, though I admire your talents and ingenuity] but it is time to replace the service with new equipment.

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