Circuit Breaker In A House Sercice Box Question

It's possible, even in a new breaker. For example, if there is an open circuit within the breaker. The lever will still work. The contacts will still be brought together and hold in that position. However, no current will flow because of the open circuit. The open circuit may not be apparent, externally.

A more likely scenario is that it is an old breaker and the contacts have been burnt away. Everything mechanically moves into place - but a gap between the contacts still exists.

A good sniff will often detect that internal overheating and burn has taken place.

How common? If the breaker has been tripping on overload several times an hour, almost inevitable. If the breaker hasn't tripped for years, pretty rare. If the breaker is cheap imported crap - well, there are some things it is worth paying for quality and anything to do with electrical safety is one.

-- Sue

| Is it possible that when a circuit breaker in a service box opens due to a | short in the circuit that it is controlling, that the lever does not (also) | move to the other position ?

I've seen such breakers. My guess is that the design has an internal only mechanism to release the spring. Such a design would also allow the breaker to trip when the human is trying to close it onto a shorted circuit, and be sure it can open back up despite the human trying to force it to close. The human has to flip the level back to the off position to catch the mechanism to try closing it, and re-tensioning the spring, again.

If a breaker (and I've seen these, too) flips the lever, it MAY be possible to manually hold the breaker into the closed position despite the short circuit condition, which could cause serious problems. I would not want a breaker that does that.

| e.g., that there might not be any visible indication that it has tripped ?

I know Square-D has breakers with a red indicator when the breaker tripped. The movement of the internal mechanism simply shows a part painted red in a visible window area. You can't see it in the dark. Use a flashlight.

| If so, is this fairly common with circuit breakers in a house service box ?

I have no idea how common.

| Likely ?

Sure.

| Why ?

Why not? See above.

Breakers are designed to "trip free" so you can't hold the handle closed to prevent the trip. They do move a little but not all the way to the off position if not held. You have to turn it all the way off to catch the mechanism and then turned back on.

This is a GFCI but it uses the same mechanics as a regular breaker on the left side. You can see the copper colored contact arm is not directly connected to the handle

Do not ever trust a circuit breaker. I have seen a 400 ampere circuit breaker on 480 volts three phase in the off position when the circuit was still hot on the load side. An electrician with 32 years of experience working next to me got a serious arc blast with molten metal flying all over him as his 10 inch screwdriver was reduced to a stub. Circuit breakers fail and fail often. At one fuse seminar by Bussman the Bussman representative stated that circuit breakers are no longer listed if they experience only one, yes, only one, short circuit on the load side.

| Do not ever trust a circuit breaker. I have seen a 400 ampere circuit | breaker on 480 volts three phase in the off position when the circuit | was still hot on the load side. An electrician with 32 years of | experience working next to me got a serious arc blast with molten | metal flying all over him as his 10 inch screwdriver was reduced to a | stub. Circuit breakers fail and fail often. At one fuse seminar by | Bussman the Bussman representative stated that circuit breakers are no | longer listed if they experience only one, yes, only one, short | circuit on the load side.

Sounds like a motivated statement. Is there anything available to support his statement that you know of? Or is he just trying to lower circuit breakers to the level of fuses (which I could easily believe will lose their listings once subjected to merely one short circuit event).

| When breakers in the box are tripped, the lever moves off the line of the ON | breakers -- it does not move to the full OFF position. | | As you sight down the line of breakers, they all line up except the one that | is tripped, it is slightly off the line. This is normal operation. | | To reset a tripped breaker, you must move it by hand to the full OFF | position then back to the ON position.

I once lived in an apartment with some old GE brand breakers that did not do that at all. When they tripped, there was no displacement of the handle at all. You could not see which breaker had tripped. But once you figured it out, the above reset method you described would work. One thing I did notice was that the mechanical force against flipping the breaker to the off position was less for the tripped breaker.

| I have never seen a tripped breaker that was not off the line of the | remaining ON breakers. I suppose it could happen, but I've never seen it. I | have seen some that unless one was expecting the tripped breaker to be off | line relative to the ON breakers, the amount that it was off was barely | discernable. But knowing that a tripped breaker does not line up with the | set ones makes the tripped ones easier to find.

I was quite used to tripped breakers being a bit off the line just as has been described. But this one panel really was NOT like that at all. It is also the only GE panel I have seen and it was rather old (the building was built in early 1950's). When I run my finger up and down the line of breakers I can feel which one is tripped easily on normal modern panels. This one just didn't have that "feature". For planned new construction I will be going with Cutler-Hammer, so I won't have that issue, anyway. As for my current place, with Square-D HOM breakers, we haven't had any trip so I can't verify these (I have manually switched them all off and back on, including the main, about once a year).

| Your experience with the breaker tripping but not moving reinforces the OP's | experience, he found a tripped breaker that was not in the OFF position. A | tripped breaker does not move to OFF.

I don't know if he checked for the slight position change or not. I just pointed out my scenario since it seemed there was an assumption that all breaker models do that. That may be true of all modern models. But it is definitely not true if older models are included in the consideration.

Also, not all breakers in the panel will be of the same mfr. This means, in my experience, that the handles will be slightly different, lining up -- or not -- a bit differently.