It's exactly what it says on the tin.
You have an arc fault somewhere.
An arc fault is either a) two wires/things that are *supposed* to connect well, not connecting so well (series arc fault)... or b) two wires that are not supposed to connect occasionally arcing between them (parallel arc fault). Generally you're up against the first one, but the second is always a possibility. Usually the second will trip a GFCI.
You could actually *hear* arc faults if you could listen to the signal on the wire. If you've ever hooked up speakers or plugged in headphones with the power on, and heard sort of a crinkle-crunch sound, that's what arc faults sound like. That is what the AF breaker is listening for.
A switch can be a candidate for this sort of thing, because a hesistant throw of the switch (especially off) can cause power to arc arcoss the gap.
When they invented arc-fault breakers, the concept was to protect bedrooms from electric blanket failures, appliance cord damage from furniture being mashed into them, that kind of thing. But what actually happened was they revealed wiring faults in the walls (virtually all at wire ends):
- Top of the hit parade is the backstab connection. That's where the wire jabs into a hole, which auto-grabs it. Never use those.
- Second is weak wire-nutting. A lot of people find their wire-nut work tends to "fall apart" unless they tape the nut to the wires. That is a poor connection, and causes arc faults. They misunderstand how wire-nuts work, and their technique is quite bad, and they should fix their technique. The proof of the pudding is a pull-test: Hold the nut in one hand and pull hard on each wire in turn. Pull hard enough that you can't hold onto the nut anymore. If the wire comes out, it was a poor enough connection to cause arc faults. Tape over wirenuts is a yellow-flag, because it's how Johnny Limp-Wrist covers his bad technique. But there are legit uses for tape, especially if the nut is capping a single wire.
- Third is limp-wristed under-torquing of screw terminals on receps, switches, neutral bar or breaker.
Almost any splice method can be done wrong, except for backstabs, which make their own "wrong".
You should also evaluate socket connections. An appliance whose plug fits poorly into a socket can cause arc faults, that usually means the socket is worn out.
Obviously the original purpose of AFCIs, worn/damaged cords, is valid too.
And appliances *can* have arc faults internally, or they can falsely trip AFCIs. So if you have an appliance which "cycles", such as a dehumidifier on the circuit, that's a place to look.
Generally you're up against *series* arc faults, where things that are supposed to connect aren't doing so reliably. Here's the takeaway: series arc-faults only happen when current is flowing. So your electric blanket, which is OFF, cannot be a source of a series arc fault. If power comes from the breaker to receptacle 1 2 3 etc., and nothing is plugged into receptacles 4, 5 and 6, then a series arc fault there is highly improbable.
Oh, and there's one more wrinkle to this odyssey. Remember how I said that you can "Hear" arc faults on the wires? Well, AFCIs can "hear" arc faults *on other circuits*. So something "loudly" arc-faulting on another circuit absolutely can trip this AFCI. That generally only happens with circuits on the same pole. Most panels have poles laid out like this. There are other layouts, but you can't get AFCI breakers for those.
You have an arc fault somewhere.
An arc fault is either a) two wires/things that are *supposed* to connect well, not connecting so well (series arc fault)... or b) two wires that are not supposed to connect occasionally arcing between them (parallel arc fault). Generally you're up against the first one, but the second is always a possibility. Usually the second will trip a GFCI.
You could actually *hear* arc faults if you could listen to the signal on the wire. If you've ever hooked up speakers or plugged in headphones with the power on, and heard sort of a crinkle-crunch sound, that's what arc faults sound like. That is what the AF breaker is listening for.
A switch can be a candidate for this sort of thing, because a hesistant throw of the switch (especially off) can cause power to arc arcoss the gap.
When they invented arc-fault breakers, the concept was to protect bedrooms from electric blanket failures, appliance cord damage from furniture being mashed into them, that kind of thing. But what actually happened was they revealed wiring faults in the walls (virtually all at wire ends):
- Top of the hit parade is the backstab connection. That's where the wire jabs into a hole, which auto-grabs it. Never use those.
- Second is weak wire-nutting. A lot of people find their wire-nut work tends to "fall apart" unless they tape the nut to the wires. That is a poor connection, and causes arc faults. They misunderstand how wire-nuts work, and their technique is quite bad, and they should fix their technique. The proof of the pudding is a pull-test: Hold the nut in one hand and pull hard on each wire in turn. Pull hard enough that you can't hold onto the nut anymore. If the wire comes out, it was a poor enough connection to cause arc faults. Tape over wirenuts is a yellow-flag, because it's how Johnny Limp-Wrist covers his bad technique. But there are legit uses for tape, especially if the nut is capping a single wire.
- Third is limp-wristed under-torquing of screw terminals on receps, switches, neutral bar or breaker.
Almost any splice method can be done wrong, except for backstabs, which make their own "wrong".
You should also evaluate socket connections. An appliance whose plug fits poorly into a socket can cause arc faults, that usually means the socket is worn out.
Obviously the original purpose of AFCIs, worn/damaged cords, is valid too.
And appliances *can* have arc faults internally, or they can falsely trip AFCIs. So if you have an appliance which "cycles", such as a dehumidifier on the circuit, that's a place to look.
Generally you're up against *series* arc faults, where things that are supposed to connect aren't doing so reliably. Here's the takeaway: series arc-faults only happen when current is flowing. So your electric blanket, which is OFF, cannot be a source of a series arc fault. If power comes from the breaker to receptacle 1 2 3 etc., and nothing is plugged into receptacles 4, 5 and 6, then a series arc fault there is highly improbable.
Oh, and there's one more wrinkle to this odyssey. Remember how I said that you can "Hear" arc faults on the wires? Well, AFCIs can "hear" arc faults *on other circuits*. So something "loudly" arc-faulting on another circuit absolutely can trip this AFCI. That generally only happens with circuits on the same pole. Most panels have poles laid out like this. There are other layouts, but you can't get AFCI breakers for those.
