Humidity and problem electric circuit

Old 05-18-18, 04:48 PM
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Humidity and problem electric circuit

I'll try to be a brief as possible here...

I bought a 1906 very large Victorian 2.5 years ago.

It's got 200amp service with several service panels. The house has been upgraded over the years - the oldest wiring is metal-clad BX. Much of the house has newer Romex installed in the early 2000's. It's a priority of mine to replace it all, but its a 7,000 square foot house with very elaborate woodwork, so not exactly an easy task.

Last year I had a circuit go out for no reason. The circuit is all over the place. Everything from ceiling fixtures on the 2nd floor to lamp posts outside. I had 2 electricians come in, who just threw up their hands and couldn't figure it out. When they tested back feeding the system, everything worked...very odd. This circuit is mostly the old BX. 4 weeks later, like magic, the circuit started working again. I had tried several random things, like replacing recepticals, etc., so I figured it was something I did.

This happened again last spring. Same circuit. It was around the time I start up the dehumidifiers in the basement, and the day after I started up the dehumidifier, whamo - circuit works again.

I thought it might have something to do with humidity and condensation.

Fast forward to yesterday. Crazy humid and rainy weather in the Northeast. Humidity went from like 15% to 65% in my house in a few days. BAM! I come home, and the circuit is out.

Does this happen? I'm thinking this has to be condensation / humidity related. I started up the dehumidifiers, and hopefully that will do something. I can't find any condensation related issues online.

The odd thing is, the 200amp service panel is in the room with the dehumidifier int he basement, but i don't have the issue on any of the other circuits, and this circuit is actually run off of a service panel on the 2nd floor, which is run from the main panel in the basement, and the service panel has 8 circuit on it. It's odd that I only have this problem with one. There are a few junction boxes in that room, maybe one connected to that circuit.

Do you guys thing I'm barking up the wrong tree with this condensation theory?
Old 05-18-18, 06:22 PM
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Could it be humidity related..... possibly but not likely.
Usually it's more of a connected load issue. When the circuit gets loaded... it goes out.

I've done work in old houses where a single circuit appears all over the house. It wouldn't be so bad if the problem was at a device but many times there are buried junction boxes or in out of the way locations.

The only thing you can really do is to identify everything that's on that circuit. When part of it fails.... see what's still working. You may be able to locate a problem area as it's usually at the last working location or the first dead location. All bets are off if there is a hidden junction box.
Old 05-19-18, 06:41 PM
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Thanks for the reply.

What gets me is, in this case, the circuit was working when I left, and when I came home it was off. No thrown breaker.

What conditions would cause a circuit to be loaded?

I was doing some landscaping today, and saw what looked like Romex going directly into the ground (!!!). I think I may there may be an old floodlight buried somewhere in the front flower bed. Could that be causing the issue? We've had a lot of rain here, so i'm not going to go digging around until (atleast) the weather dries out a bit.

Sooo hard to trace things here. I asked the previous owner (who had lived her since 1974) about a switch that seemingly went to nothing, and he said "Honestly, I lived there for 42 years, and never knew where that switch went to ".

Old 05-20-18, 05:02 PM
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Loose connections can definitely cause what you're seeing. Easy to fix - once you find the offending connection. Unfortunately, it could be in the attic, basement, or hidden behind a wall (which of course it shouldn't be).

I've seen underground wiring cause GFI trips, but usually, once it trips, it's off until it gets reset. I wouldn't think it's an off/on kind of thing.

Good luck tracking it down!
Old 05-21-18, 10:13 AM
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Humidity went from like 15% to 65% in my house in a few days. BAM! I come home, and the circuit is out.
This would opposite of what I would expect. Typically the more moisture there is the better a loose connection.

I agree that there is a loose connection someplace. Could be on the hot or neutral side. I troubleshoot similar issues in large parking lots and strip malls. Regardless of the size of the house, a good electrician should be able to troubleshoot this when it is not working. It is difficult to troubleshoot when things are working.
Old 05-23-18, 11:18 AM
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I guess I'll play some Sherlock Holmes this weekend.

I did notice something very interesting.....there are 3 light switches in the 2nd floor hallway, about 5 feet from the breaker box. It seems to control lights on atleast 2 breakers. 1 switch controls a hall light on a circuit that is working. Another is definitely controlling the light on the dead circuit. The 3rd - well i don't even know where that goes . I asked the previous owner, who lived her for about 40 years, and he said "Honestly, I never knew what that was for." I'm wondering if there was another light somewhere - either in the ceiling or on the wall, that was deleted.

I created a spreadsheet with all of the circuits, and each outlet / light that they control, but its a 7,000 sq foot house so i could have missed something, like one of those lights that switch on when I open a closet :-\

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