For the first time in my life I’ve had a circuit breaker fail. I didn’t even know they did that. The breaker tripped, I tried resetting it but it felt “loose” and wouldn’t click into the on position, and the circuit remained dead. I got a replacement breaker, swapped it in, and now the circuit is working again.
So what actually happens inside the thing when a breaker goes bad?
Can’t answer the question, but share the experience.
All electromechanical things fail eventually.
Here’s a youtube autopsy of a British one, by your friend and mine, Big Clive.
Just had an electrician out today to replace a breaker. I believe his exact words were “it was pretty much melted.”
Apparently when they built our house, they put all the GFI outlets (bathrooms, garage, outside) on the same 15A circuit. We discovered this when my wife bought a plug-in hybrid last summer, and kept tripping the breaker every time she dried her hair while the car was plugged in.
Got to the point in the last couple weeks that the breaker would trip from either the hair dryer or the car. We made an appointment with an electrician to come out and replace the breaker for the bathrooms and add a new one for the garage. A couple days later, the breaker tripped just from turning the bathroom lights on. So we just left it off until the electrician got here today.
Circuit breakers do wear out, just like anything else. Generally takes decades, though.
A couple of things can increase the chances of early failure:
There’s a couple little cam/lever/springy things inside that let the breaker trip on either thermal or magnetic. Thermal for overload and magnetic for shorts.
Probably something gives up at “B” or to the bottom right of “D”
One of my first jobs while studying electrical engineering in college was at a Square D circuit breaker plant. My job was to apply direct short circuits to breakers and make sure they would continue to function properly. It’s amazing the beating they can take.
Did you consider installing a GFCI breaker and eliminating the GFCI receptacles?
They certainly do fail and do get recalled. I rewired our 1917 house to replace knob-and-tube wiring, and to bring it up to code I had to install some arc fault circuit interrupters / circuit breakers. I installed a pair of them, and one would trip frequently and randomly. Only by swapping the breakers did I conclude it wasn’t my wiring that was at fault, but a bad breaker. A Google search for breaker recalls brings up lots of results.
I returned mine to where I bought it, Home Depot, and they immediately exchanged it with no questions asked, some six months after I bought it. It seemed like they had more than just a few get returned.
Didn’t really give it much thought. We just knew we had to get the garage on a separate circuit.
I replaced a failed circuit breaker once. I am not an electrician, but I am sometimes a cheapskate. It was scary. Luckily no one was watching; my every move was choreographed and precise. And I was sweating.
When they fail, do they “fail safe”? That is, when they fail, do they cut power, or, when they fail, will they no longer cut power, no matter how much power is drawn? (You can see that the latter is a Very Bad Thng.)
They don’t always fail safe.
Most of the time they will, but the key word there is “most”. The most common types of failures are in the latching mechanism, so they’ll trip at lower currents than they are supposed to trip or they’ll fail to stay closed when you try to reset them.
They can fail in such a way that they won’t open, or they can fail in a way that makes them slow to open, slow enough that the fault current that flows can do a lot of damage.
For example, you can have a failure in the spring, and that could cause the breaker to stay closed when it should be opening the circuit. If you have a lot of arcing internally you can also basically spot weld the contacts together so that the breaker also won’t open when it should.
As Tim@T-Bonham.net said upthread, the two things that can drastically shorten the life of your breakers are consistently high currents just below the trip threshold, which cause overheating and damage, and excessive tripping. Every time a breaker trips you end up with some arcing of the contacts, which builds up carbon deposits on those contacts. You can end up with poor conductivity between the contacts, resulting in hot spots and overheating, or again, you could possibly end up spot welding the contacts together when you close the breaker.
More often than not though, the breaker just fails to stay closed, at least in my experience.
Usually, but there are a couple well-known exceptions to this. Zinsco and Federal Pacific were two of the worst offenders at not tripping out when overloaded. Hopefully by now there’s not too many of either brand still in use.
I frequently deal with breakers that are subjected to excessive tripping and overloaded circuits. They usually become weak and loose and will not stay reset. They also may arc, overheat, melt, etc… as parts wear out.
It’s unbelievable how many people will trip a breaker and then go flip it back on without a second thought as to why it tripped. It’s a safety device not a light switch. You need to eliminate the cause of the overcurrent before resetting a breaker or someone’s in for a shock.
One other possibility that hasn’t been mentioned.