The house has three floors, on the first floor is my office and on the third is my bedroom. The bedroom has two breakers, one going to the outlets and the other (which is shared by the other bedrooms) going to the lights. The office has two breakers, one going to the lights and UPS which powers the computer stuff, the other going to the laser printer.
Now, it’s been this way for ages, never a problem. However, today, for some reason the breakers to the bedroom outlets and to the laser printer tripped. I can’t imagine why, as the printer wasn’t even plugged in and the only thing running in the bedroom was a fan. I try resetting the breakers only to discover that, while I can switch one on, when I try the second, they both trip again. Either will work: I can run the printer, but not the fan; or the fan, but not the printer.
I don’t understand that. The circuits are in no way connected–I can’t see why something on one would influence the other at all. They’re not overloaded–one wasn’t powering anything when it tripped, and the fan on the other has run fine before and continues to run now that I’ve dragged an extension cord from the hallway. Even disconnecting everything, though, it still won’t allow both to be on simultaneously. I imagine I’ll be calling an electrician, but can anyone tell me where the problem is?
Have you had any work done in your electrical panel lately? My first impression reading this is that it could be a loose neutral, those can cause a wide variety of odd problems. Is the laser printer on a breaker all by itself in the office or am i reading that wrong?
While it doesn’t happen often, you may have a defective circuit breaker. What is more likely is that there is a problem in the branch circuit wiring, either in a device box, or perhaps a nail used to hang a picture 10 years ago or an overdriven staple which partially damaged the NM cable running along a stud has finally rubbed through from building expansion and contraction, and is now causing a fault.
Yes, something is causing a fault between the two hot lines running from the breakers; it could be in the load center itself, or anywhere in the branch wiring. Evidently, these breakers are connected to opposite legs, so there exists 240 V (or less commonly, 208 V) between them, but only when both breakers are on. This is why you can turn either one on by itself, but both together will cause a trip. It’s perhaps a blessing in disguise, because if the two circuits had been on one leg, you’d never have noticed this fault under normal circumstances–and it could easily have worsened over time and ultimately caused a fire.
Has any electrical work been done in the house recently? Any outlets or switches replaced?
I’ve seen a couple cases where a receptacle was replaced without breaking off the tab that normally joins both sides - this was one of those dealies where one side of the outlet is always on, and the other side is controlled by a switch.
When the light switch was flipped on, KAPOW! resulted as both hots were shorted together. One particularly memorable case at my brother’s house tripped two 15-amp breakers, plus the 50-amp breaker feeding the subpanel. (Mechanical engineers shouldn’t mess with wiring!)
An electrician will be here next week, until then I’ve got the office on and bedroom off. I just asked here because I was very curious what might be the cause of this problem.
No work has been done to the bedroom for four years, when I moved in (the whole house was rewired). The office has had a new outlet put in a couple months ago, but nothing unusual, just a second one coming off of the first to allow me to move the printer to the other end of the desk without having to use an extension cord.
Yes, the laser printer is by itself–it uses nearly the whole 15 amps when starting, not much else could share the circuit with it. But again, it wasn’t even plugged in at the time.
I hope you’ll post to let us know what the electrician finds. Re-reading the thread I think danceswithcats is on the right track, that’s not the type of thing I see in my field so much. Circuit breakers (non-GFIs) have two trip ratings, one for overcurrent and one for short circuit, it sounds like yours is tripping on the short circuit. The loose neutral idea I mentioned is more likely to ruin the fan than trip the breaker but will cause spurious breaker trips as well, usually under load though.
Thanks for the update. I was curious to hear what he would find. Circuit breakers fail just like anything else. I’ve only seen them fail in the off position but I don’t have to deal with them very often.
Curiosity question-what is the brand of panelboard and type/ampacity of circuit breaker? Did the electrician leave the replaced breakers with you?
I’m asking because UL and the CPSC have identified knock-offs of brand name circuit breakers bearing counterfeit UL markings, and wonder if yours are one of them.
I regret not answering your OP now that I see your follow up, could possibly have saved you some money. The reason was the answer being un-Dope like.
Conversation with electricians and my own observation have shown that CB’s can get ornery for no apparent reason, perhaps a prolonged static condition or microscopic dust ? The simple solution being to flick them a couple times. There is a descriptive term for the condition but memory doesn’t serve.
As Danceswithcats notes, some brands seem prone to the condition, though none counterfeit IME.
Personally, when I encounter a flaky breaker, I just go ahead and replace it. They are absolutely dirt cheap compared to the potential cost of one which fails to work when it should. Generally, they do fail open, but for $10 I’m not taking the chance.
I agree, it’s just not worth the risk. My breaker panel needs to be replaced and I’ll probably spend the extra money to replace many of them with arc fault breakers for the added peace of mind.
You’re lucky. There are scads of counterfeit Square D breakers that fail closed, and Federal Pacific breakers are also known for failing closed often enough that FPE lost its UL listing for their “Stab-Lok” product line. In either case, the internal contacts weld together and the breaker will not trip out on an overload.
There are aftermarket FPE breakers that are ironically better than the originals, but the overall panel design is so iffy that it’s best to replace the whole panel if you can afford to.
Thanks for the info! I’ve known about counterfeit breakers for a while but this is the first I’ve heard about the FPE breakers. I don’t have them in my home but the plant I work in has several of their panels. I did a quick search after reading your post and was surprised at how far back the issues with their breakers goes. If there was a recall in Canada the information probably made it to our engineering department and is sitting in a stack of papers somewhere :rolleyes:
There’s a company now called Federal Pacific that makes commercial/industrial transformers and switchgear, but they’re unrelated to the long-gone Federal Pacific Electric company that made bad circuit breakers.
Not necessarily. I’ve read online that some company bought FPE’s tooling, and so their breakers are presumed to be just as bad as the original. More than you want to know on the subject
I found out about FPE on this board several months back. Good thing. I recently started remodeling my old house and found - yup, a Federal Pacific breaker box. Not a huge deal since I plan to replace nearly all the wiring and add several circuits, but I could do without the expense of a new breaker panel.