The Problem
A 15 amp circuit (affects living room and one bedroom) trips sporadically. It can be a few days or a few hours. I know it has tripped twice in 2 hours, and has gone nearly 2 weeks before tripping again. But most commonly it trips about once a day, typically in the evening. Nothing was just turned on, and it trips (if that happened I wouldn’t be posting). Usually we have the TV going, in both rooms and a comuter, among a few other things for a few hours, and then it trips.
To try to narrow it down, and detect the problem we have moved or turned off the appliances that were feasible.
The Troubleshooting
I have had two electricians out and both were dumbfounded. The 2nd one told me that I needed to be able to recreate it before he would be able to help. Which I accepted since that is true when debugging computer code.
The first electrican pulled the outlets and light switches to look for loose wire and whatever else could be causing the issue. However, I was not there to over see his work, so I am unsure if he actually did that on all outlets and switches
The second electrican tested the amp load on the circuit, we are running about 6 amps out of 15.
The last thing that I have tried is turning off the ceiling fan (both at the fan and at the wall switch) since it runs continually. Therefore has been on every time the circuit has tripped. It lasted nearly 2 weeks before it tripped, with the fan off. Now, I am wondering if this is a two part problem, since the tripping has increased back to once a day. (I believe the room mate / tenant) has started using the fan again. Where the problem would be the fan PLUS somewhere else.
I am going to switch out all the outlets and switches that are affected with new ones. Right now I am unsure how to continue the trouble shooting. Anyone have an idea or solution?
Replies
Try the breaker first
Try replacing the beaker first. After they trip a few times, they can get weak, and then trip at currents far below the rating, and some will just trip out for no apparent reason. So, that would be my first thing to try. I think I would probably just swap the breaker with another one in the cabinet of the same rating, and see if the problem moves. Doesn't cost anything, and is actually quicker than changing out a switch or receptacle. Just be sure not to swap for one that controls the refrigerator, freezer, or something that could be costly if it looses power.
After that start looking for a bad receptacle, or light fixture, then check switches.
Right -- try replacing the breaker. Swap wires on two adjacent breakers of the same size -- if the problem stays with the breaker then it's the breaker.
Otherwise, you likely have an intermittent short. These can be tough to find -- could be a nail through a wire somewhere, or a wire rubbing against a piece of ductwork, or something shorting out inside a box. Generally you have to disconnect pieces of the circuit a little at a time until the problem goes away, which is a slow and error-prone process when the short doesn't happen with any regularity.,
But the bad breaker's the more likely problem.
I've already tried switching out the breaker, and had all connections on the outlets and switches checked. Neither fixed the problem.
Any other options?
The circuit may have to be high voltage tested with a megohmeter. This is something a good electrician should be able to do. First the entire circuit would have to be identified, and everything disconnected. Parts of the circuit would be isolated until the problem is found.
The more common problems are cable clamps cutting into wiring, and nicks where the sheathing is removed. Then there are problems with nails or screws penetrating wiring. Also faulty devices and bare ground wires contacting hot wires.
Yep, what mark said, 1500 V megger test. You likely have a short someplace from a cause likely what Mark identified.
Another option is to replace the breaker with an arc fault breaker, if you have a slightly arcing fault short it will be tripping very often!
Also, pull the problem breaker and inspect the bus bar. Sometimes a poor contact or some such has scorched the bus bar to the point that good contact cannot be made.
It would also be interesting to intentionally load the breaker -- get all the space heaters and tosters and toaster ovens and whatnot in the house and plug them in. Try for about 75% of rated current (figure about 8 amps per 1000 watts) and see if the breaker holds that.
If the breaker won't hold 75% of rated current then something like the scorched bus bar is likely.