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Trying to determine if I have a hazard I need to resolve...

I recently moved into a home where previous home owner did lots of dumb stuff. One thing I found was that in order to get more stuff wired to a generator transfer switch with limited breaker spots, he disconnected one line from the breaker and then inside the home bridged the two runs so those previously separated runs would draw off the same breaker on the transfer switch. Of course, his 15amp breaker there probably kept tripping as he had half the first floor now wired to it and so he dropped in a 20 amp breaker for that massive 14 gauge run. Ug.

I noticed the problem and have put a 15 amp breaker back in place... but not until we had tripped the 20amp breaker at least once ourselves. He surely had done the same many times before as he had 12amps worth of just incandescent canned lighting on there that I replaced with LED and still managed to trip with regular load on the other 20+ outlets on the combined run.

I also know exactly where he did the bridge and will be re-splitting the overloaded run. While I believe I have now achieved proper pairings to code (15amp breaker for 14 gauge runs), I’m wondering if I should be concerned about any damage caused to the lines during the period of over-ampped usage.

I did have one issue with a single can fixture that was on its own spur off that run that wasn’t consistently getting power on the supply line to the switch. I disconnected that single supply line from the outlet it branches from and rewired that single light switch to a different nearby run (that outlet was working just fine even while there were supply issues to the switch so I feel I’ve isolated and mitigated that issue). It seems unlikely to be related to the overloading issue given it would have only ever had 75-100 watts max load on it. It seems more likely that any damage of overloading nature would be closer to the root of the branching run where the load would have actually been 20amps. But I’ve not noticed any other supply issues and I can’t reasonable inspect the cables as it’s all behind finished wall.

My question - if I’m not experiencing any other issues, is there any more to be done? What is the likelihood I have any sort of fire hazard in the walls from previous overloading? Aside from very costly rewiring of that entire run, is there anything I can/should do to reduce risk of fire? Was wondering if using an arc-fault breaker would do anything? What do others suggest?

  • Sounds like you are on the right track and have done the right things. Don't over think this. Life is too short. – Paul Logan Dec 30 '17 at 21:19
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If there are any problems, they'll appear at the terminations first.

So as you work on that system, just keep an eye peeled for any thermal damage at terminations. Discolored wire, melted insulation, arcing, anything like that.

Truth be told, 14AWG wire is allowed for 20A - just look at the table formerly known as NEC 310.16... but this presumes 75C terminations (e.g. the receptacle will not scald your child's finger if he touches the outside while a wire is cooking away at 75C on a screw) and a bunch of other favorable factors. So there is a statutory rule elsewhere in NEC that clamps 14AWG ampacity at 15.

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    I believe the 240.6 small conductor rules are due to short-circuit protection issues. It doesn't change the main thrust of your point, though. – ThreePhaseEel Dec 31 '17 at 2:45
  • I agree also there is a huge safety factor for residental, if the terminations look good at the first few junctions from the panel it should be fine, off the top of my head industrial control panels can go to double or more inside the panel compared to residential. – Ed Beal Jan 1 '18 at 13:36
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I’m wondering if I should be concerned about any damage caused to the lines during the period of over-ampped usage.

It is possible the life of the insulation has been shortened by overheating the wire.

However, since you have reinstalled the 15 amp breaker this will protect the conductors from any further overloading and overheating. I agree with Harper that the terminations would most likely be the first point of failure. If your white wires are now brown that would be a sure sign of baked insulation.

Otherwise, I think you will be just fine especially if you reduced the normal load on that circuit.

Good luck!

  • Thanks all! Really appreciate the info and feedback. I’ll check the terminations on the junctions closet to the panel and call it good if they look fine. This gives me peace of mind! Thank you! – Brian Mesh Jan 2 '18 at 3:55

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