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I have a 15 amp circuit that runs to the laundry room and has on it:

  1. An indoor receptacle with a lamp plugged into it
  2. An indoor receptacle with an exercise bike plugged into it
  3. An indoor receptacle with a gas dryer and gas washer plugged into it
  4. An outdoor receptacle that rarely has anything plugged into it
  5. A motion sensor light on the exterior of the garage

This setup has worked without any issues since we've owned the house (~7 years) and the outdoor receptacle was installed off this circuit by a professional electrician about 5 years ago and is in a hefty outdoor box under an eave with appropriate caulking, etc.

A few weeks ago the washer cut out mid-way through a wash. Using a multi-meter I measured a severe voltage drop across the hot and neutral, which reported ~60v. The lamp would turn on but it was very dim. We ended up using an extension cord to reach an outlet on the other side of the garage, which is on a different circuit, and completed the laundry.

What is odd is that the next day the circuit that was reporting ~60v was now back to 120v. The laundry machine would run again and we did a load without issue. The lamp was back to full brightness. I checked all three indoor receptacles for any loose connections, but they all seemed good. Nevertheless, I replaced all three. I also checked the motion sensor light and the connections were tight, there was no moisture or other issues with the junction box the light was installed on, etc. (I did not replace the light, but reconnected everything and put it back the way it was.)

The next weekend when we did another load of laundry the same problem happened: midway through the wash the washer cut out. This time the voltage reported ~40v, for whatever that's worth. Again, we used the extension cord and did several loads of laundry. I checked the circuit a few more times throughout the day and the same problem persisted - ~40v reported from hot to neutral and a dim lamp. The next day, however, the circuit was back to reporting 120v across the hot and neutral, the lamp shone brightly, the washing machine would turn on with the previously faulty outlet.

What is going on here? My questions:

  1. It seems that the voltage drop happens only when using the washer, but it doesn't happen right when the wash starts, but midway through the cycle. But if it was the washer that was causing the problems, why does it work on another circuit?
  2. Why does the voltage drop happen and persist for several hours and then miraculously resolve itself? I would expect that if the drop was due to a load on the circuit that once the load was disconnected or off the voltage drop would repair itself. If the drop was due to a loose connection or faulty wiring then the issue wouldn't resolve itself until that loose connection or faulty wiring was addressed.
  3. Is there anything else I can try before calling a professional electrician? (I'm not comfortable mucking around at the service panel. Also, I'm too old / not interested in crawling up in the attic. I'd rather pay someone to do that, lol.) And what is the electrician going to be looking for? I worry this is going to be a very expensive repair since I (perhaps incorrectly) presume they're going to need to spend significant time trying to track down what, exactly, is the issue.

Thanks

  • I would guess overload is causing some heating and contracting, and some minor movement is effecting a poor connection. – NoSparksPlease Feb 23 at 16:42
  • How exactly did you check the connections at the receptacles? Did you look at the wires for arcing or discoloration? Did you tighten the screws? – Harper - Reinstate Monica Feb 23 at 17:52
  • @Harper-ReinstateMonica: All of the receptacles had the wire firmly shepherd hooked around the screws. I replaced two of the three interior receptacles myself (they were older ones that were installed before we moved here). I left the other interior receptacle and exterior receptacle, as those were professionally installed ~5 years ago and they both looked w/o issue per my inspection (screws tight, no discoloration, etc.). – Scott Mitchell Feb 23 at 19:25
  • Did you check the voltage at all the outlets to see if they were all low? Are you sure there aren't some outlets on that circuit you don't know about? – JACK Feb 23 at 19:52
  • You said 12 amp circuit 120v did you mean 12 awg wire? 12 amp would be unusual in some parts of the world and 12 awg wire would not be backstabbed, just caught that after re reading. – Ed Beal Feb 24 at 16:18
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The issue was with the breaker at the service panel.

I replaced the breaker with a new one and since then we've not had any voltage drops.

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  • What make and model was the breaker in question? – ThreePhaseEel Mar 3 at 3:09
  • @ThreePhaseEel - it was a Murray 20 Amp Single-Pole Type MP-Circuit Breaker. – Scott Mitchell Mar 3 at 16:33
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When the outlets/receptacles were installed, replaced were the backstabs used or were the wires shepherd hooked around the screw terminals? The backstabs are notorious for failing and causing exactly the type of problem you're experiencing. You need to check all the outlets and correct this if in fact backstabs were utilized.

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  • I checked all of the outlets - the three interior ones and the one exterior one - and all used the wires shepherd hooked around the screw terminals. There were no backstabs used. – Scott Mitchell Feb 23 at 19:23
  • It could be in the panel also, at any junction on that circuit ether hot or neutral , even the breaker itself can cause this but the most probable cause is a back stab you may not know about , I would check the voltage at the panel next time that will help narrow the issue down. – Ed Beal Feb 24 at 16:16
  • @EdBeal - it was indeed the breaker. I replaced the breaker about a week ago and since then we've done ~5 loads of laundry without any further issues. – Scott Mitchell Mar 3 at 1:24

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