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My elderly mother lives, alone, in a townhouse (basement, full first floor, second floor "loft" type arrangement) in the United States. Construction date unknown, but probably 1990s.

She has twice experienced what I describe as a partial and temporary loss of electrical power: Electricity went out in some or all of the top floor, but (she swears up and down) stayed on for the main floor, and eventually returned on its own some minutes later. (This is an intermittent, not a persistent issue. We're uncertain what is causing it except speculation about a treadmill listed below. We can't cause the issue on demand and it does not last long enough for me to drive 45 minutes to check it out.)

This is not consistent with a local/neighborhood power loss because of the partial nature of it. I am not aware of, and the breaker box does not seem to support, and weird dual feeds, there's just one 100 A main breaker for the house.

This is not consistent with tripping a normal breaker because she did not reset the breaker. I would know, I would have to walk her through that process; and I looked at the breaker box this afternoon and everything appeared normal.

There is no generator or other back-up power supply, much less one that only works in certain rooms.

The only recent change is the movement of a treadmill (which never goes faster than the lowest setting of about 1 mph) from the basement to the room she was in; the treadmill was in use both times. The treadmill outlet is not GCFI.

There are only two situations I can think of here:

  1. I am aware that self-resetting breakers exist. I'm not sure if they would ever be considered up to code for a residential building, or if they look any different from a normal breaker. (This is farfetched, to say the least. But my father, before he passed, was a licensed union electrician for 40 years. He never mentioned doing anything like that, but if it would be up to code, it is at least theoretically possible. I would stake my life on the fact that he would never do anything not up to code anywhere, much less his own house.)

  2. A loose wire somewhere on the circuit, probably where the treadmill is plugged in which is getting knocked out of position either due to the vibrations of the treadmill or thermal cycling from the new current draw. Either of which would be very bad.

Am I missing some other possibility?

(In fact, the real subtext of the question is, "Do I need to get an electrician out there Monday morning to hunt for the loose wire/fire hazard?" But that's not a good title for a question.)

PS - The treadmill is off-limits until this is sorted out.

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    The key troubleshooting is to figure out whether this is (a) a single circuit partially or totally going out (which would point to a loose wire somewhere that disconnects when it heats up too much or vibrates too much etc. and eventually gets back in place on its own) or (b) everything on one hot leg going out, which would likely affect multiple circuits (roughly half the 120V stuff in the entire house) and would cause strange things to happen on any 240V equipment (typically water heater, HVAC, electric cooktop/oven, clothes dryer). May 16 at 2:45
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    Yes -- do any 240V appliances (such as a water heater, electric range, central air conditioner, or clothes dryer), or things on other circuits, have issues when this happens? May 16 at 3:15
  • Unknown, but we'll watch for it. It's only happened twice and my mother has limited (but not zero) mobility, making it difficult for her to quickly check these things. Would these devices tend to revert to normal functioning if it's a phase issue? If yes, it just might not be possible to get a solid answer.
    – Reader
    May 16 at 3:40
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    Do you know how to spot a 240V breaker? Try turning all of them off and check the flaky areas of the house again. Are they now stone dead? <-- points to "Lost Phase" which the power company will fix for free. May 16 at 7:50
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    If she occupies an entire townhouse the following is unlikely, but still: Make sure the affected outlets are not fed from the panel in a different unit or different part of the building. You can do that by waiting until it's working, and turning off your main breaker. If parts of the top floor retain power, you have this problem.
    – jay613
    May 16 at 16:17

2 Answers 2

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In this case, the power outages were indeed the loss of a phase. The cause of that was the 100 amp main breaker which was old (25 - 30 years, or thereabouts) and becoming somewhat corroded-- not unusual for this climate.

We're uncertain what was causing the power to turn off at any given time, but it could have been something as simple as thermal cycling or environmental vibrations from nearby truck traffic causing slight movements. Either would appear random.

It's been a week and a half since a qualified electrician removed and replaced the breaker, inspected the rest of the panel for damage, and packed the pipe off with putty to try and reduce future moisture. There haven't been any incidents since then (and they were starting to happen daily or more than daily) so this is as certain anyone can be that the cause of an intermittent problem has been solved.

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I have experienced similar situations on three different places. All of them where related to "false contact" or some wires in the main feed being broken or damaged due to traffic accidents or vandalism/pranksters or a failed meter or meter enclosure.

A loose wire, a "false contact", a partially broken conductor or similar, can cause that some parts of the house lose power. The main giveaway is that more than one circuit is affected at the same time, that is, the partial outage would look the same as if you turned off several breakers at once but not all of them.

The other hint is this: Most of the breaker boxes used in my country (and I believe The U.S. is very similar) alternate the phase from one breaker to the next, so that it is easy to create a 220v circuit using a double gang breaker. So, if you turn off every other breaker, and check where power goes off and where not, you can "guess" which circuits are in one phase or the other.

I would say, you could try the trick of turning several breakers and try to replicate the partial outage to the best your mom can describe. If it happens that you make an alternating pattern (on-off-on-off...) then it is likely one of the main conductors on the breaker box is not properly tightened (or worse).

The other alternative, is to use smart plugs or some device than can log power usage/outages. I have seen at least one advertisement claiming you could use a logging feature of the device to find out whether an outage had happened (...). This can serve you to find out if the issue happens even if your mom is unaware (e.g. at a time where all lights are off and almost no device is being used)

Of all the times I've seen this happen, the weirdest one occurred on a small apartment building I lived for a while. A false contact in the electric meter box caused a phenomenon where we would think when where out of power, but once, I "forgot" we where in "outage" and tried to turn on one of the burners on a 220v range stove top. When I did that, the kitchen light went on. Given that I had seen similar behavior during my parent's house incident, I went to investigate and eventually found out that the meter was partially dislodged. I pushed it back the best I could and "problem solved". That happened a few times more. I don't know whether it was a malfunction of the enclosure or if a prankster was pulling the meter out of placement.

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  • Years ago (about 60) I built a new home and installed a 225A system. Everything worked great until one summer day (AC was on) I started my Air Compressor and it shut down about 1/2 of my home and the neighbors. Poking around I found I was losing power on the incoming phase. I called the power company and was told I was nuts but they eventually sent somebody out and when I showed them they knew what to do. They replaced the transformer with a larger one and the problem went away along with the blinking lights etc.
    – Gil
    May 17 at 2:01

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