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I live in a mobile home, first issues I've had electrically. I noticed the lights would dim from time to time, a fan that was in the bedroom would run like it was on low even though I put it to the highest setting. First thing I did was called utility company to come check meter readings and such and he said they had good voltage even with everything on with no fluctuation. He told me to get a reading on the breakers in the box and see what I could come up with. Borrowed a good meter from work and checked the breakers, the main, a double pole which is a 100amp breaker (assuming since it says 100 on the handle for both) is the first I checked. The bottom one reads a constant 118 and the top would go from that range down to 78 during the dimming of lights. Is this just a bad main breaker that isn't letting the full juice through? Calling an electrician tomorrow but figured I'd get some feed back from here just in case someone else is having a similar issue. The home itself is only 15 years old. Possibly not balanced correctly in the box?

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    Hello, and welcome to Home Improvement. Has this behavior changed, or was it always this way? And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Sep 3 at 11:03
  • What make and model is the panel? Also, when you said you checked at the main, were you checking the incoming lugs on the main breaker, or...? – ThreePhaseEel Sep 3 at 23:05
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I have had breakers develop high resistance at the hammers ( the connecting device) in some cases if not two much arcing turn all the smaller breakers off, then flip the main breaker on and off 10 times, this can clear the carbon and reseat the hammers on the contact. If it works but starts doing it again after a while the breaker is failing and needs to be replaced. What brand of panel and type of breaker would be my only question in some cases the brand itself may justify replacing the entire panel.

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    federal pacific??? lol – JACK Sep 3 at 15:08
  • Yes FPE, some also say Zinsco but I haven’t had breaker problems only buss issues with them. I put a zinsco in my mom’s place back in the 70’s, I used a corrosion inhibitor on the buss and it still looks new, but I have seen buss failures. – Ed Beal Sep 3 at 15:19
  • @EdBeal Read that report of ThreePhaseEel's, apparently the bus issues are only a problem for certain ones. Someone ought to take GE breaker guts and put them inside FPE breaker shells, sell them for 10% cheaper than Connecticut Electric's garbage... – Harper - Reinstate Monica Sep 3 at 16:31
  • I did not see the report is it here? – Ed Beal Sep 3 at 17:19
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I'm not sure what you mean by "bottom" and "top".

Since you know about balancing, you know you get two banks (poles) of 120V. So a main breaker should have two inputs and two outputs; the outputs go to the breaker busses, the inputs are typically fat wires.

Thus, there are 4 readings to take:

  • Hot L1 (input/utility side) to neutral
  • Hot L2 (input/utility side) to neutral
  • Hot L1 (breaker bus side) to neutral
  • Hot L2 (breaker bus side) to neutral

I would expect that only one pole is sagging, and you've already identified it.

So I would be keenly interested in whether you see that "sag" on the input/utility side of the breaker, or only on the breaker side.

If the utility side of the breaker is also sagging, then ba da bing: it can only be 2 places: between there and the meter, or between the meter and the pole. The latter is far and away the most likely, and the utility will fix it for free. But you've already tried that and they won't fess up; either they didn't see it fail, or the problem really is in your bailiwick.

I would have them pull the meter (often, they can do this remotely using the smart meter). Then, remembering that the lugs on the top half of the meter are always hot and totally un-breakered, have someone go into the meter and closely inspect the service entrance wires from the meter to the main breaker. Particularly look for corrosion on aluminum wiring, and wrong torque settings. Do the same elsewhere those wires are spliced, e.g. At the main breaker.

There's nothing wrong with aluminum wiring for service entrance wiring and feeder, but you do need to use the goop, and any wiring must have the lug torqued correctly.

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