AFCI tripping from load on other circuit
I can’t seem to find this problem addressed elsewhere, so here goes…
I’m days/hours away from finishing a small remodelling job, mostly DIY but with some trades work, including electrical rough-in and distribution work.
There’s an AFCI controlled circuit in the bedroom that’s causing me a lot of problems. First off, when I installed my Ikea purchased (I mention this because I’m thinking the cheapness of it may be a factor in this problem) sconce (with DIY switch installed) on the circuit the breaker tripped as soon as I turned it on. The breaker then wouldn’t reset. Ok. So. I removed the sconce and put the wire nuts back on the bare wires. The breaker could be reset and I figured the sconce/switch had a problem.
Now (and maybe it’s not related) I’m noticing that the breaker is tripping when high loads (shop vac, refrigerator) are placed on ANY circuit in the panel. I can have the vac plugged in downstairs and the the breaker for the upstairs bedroom will trip as soon as I switch it on.
The electrician who did the rough-in suggested that I pull/recheck all the outlets in the room (which I wired) to look for grounded neutrals, etc., but if that were the problem, wouldn’t the breaker not hold at all? Doesn’t the problem seem to point a mis-wiring in the panel, in which the load being placed on the other circuit is somehow being felt by the AFCI breaker? Is there a way to check this without going into the panel, which I don’t have the confidence to do?
Thanks.
Replies
Over 50% of the AFCI breakers we install get replaced within months of the install. The failure rate in astounding. You may have a faulty breaker. If you are not going to be inspected, I would stick to a regular breaker (I do know that AFCI are required in bedrooms) that functions.
Best of luck
Bruce
Your logic on the sconce is good, maybe a fault in the fixture wiring. Try installing a simple porcelain lampholder and see if the problem goes away. If so, it was the sconce.
As far as the AFCI tripping when a "high load" comes on "any circuit"--could indeed be a bad ACFI breaker, as Hiker mentioned. Or it could be some miswire or fault in the system. If anothter AFCI breaker does the same thing, I suggest not ignoring it and swapping the AFCI out for a standard breaker. There's something wrong, and although the system may function, it'd be prudent to find out what the problem is.
Time to call in a pro, someone with real troubleshooting skills (and when I say that, I don't mean to diss Hiker...) If there's some weird fault, it may take some time (and time = money) to find it.
That's the thing about these AFCIs. They trip under conditions that we never would have known about before...like neutral/equipment ground crosses, or inadvertantly shared neutrals between circuits. Or more seriously, there may be a high-impedance ground fault, or short somewhere. And finding something like that before it goes south is a good thing.
Cliff
Edited 7/30/2009 5:47 pm ET by CAP
No Diss taken Cliff,
I am not a fan of AFCI's and really do not see how much protection they provide.
Has anyone see an analysis of AFCI failure rate or how many lives could have been saved if an AFCI was present?
I always get a sense that the manufacturers see an opportunity make coin on the new devices and get them into code.
Bruce
Yeah, I think the breaker manufacturers aspire to be drug manufacturers.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Bruce,
It's cool, brother.
Yea, I've been told that the Code-making panel that recommended the AFCI requirement had no statistically valid data on the number of electrical fires caused by parallel (phase-to-phase) arc faults, so no idea s to the benefit of using AFCIs. It's understandable that there's no fire origin data broekn down past "electrical". Realistically, it'd be very hard to find an arc fault point of oprigin after the fire is out. All that heat and water tends to make a mess of things. Heck, most FDs classify a fire for which they can't determine a source of ignition as "suspicious, possible electrical", and that means building wiring or extension cord, or appliance...
I have seen some instances where an arcing fault occurred and it was a miracle that the house didn't burn down. Several cases of a receptacle with a loose wire at the poke-in backwire terminal, the receptacle melted to a greaer or lesser extent from the heat.
In one instance I observed, a sewing needle had fallen across the blades of a plug (that wasn't completely inserted into the receptacle). The needle burned two-thirds into the blades before the standard breaker tripped. There were soot trails on the face of the recept and running up the wall above each blade. I figure the needle probably was red hot and chattering on the blades...the room had wall-to-wall carpet (nylon), and the usual dust and stuff along the wall, and curtains right next to the outlet. It was the bedrom of two little girls, their bunk bed was right next ot the outlet. It freaked me out thinking what might have happened.
I can't tell you if an AFCI breaker would've tripped sooner in any of the instances where I've seen evidence of arcing in a branch circuit. I've never seen an AFCI breaker demonstrated, but a guy I trust, Mike Holt (http://www.mikeholt.com), did witness some AFCI breakers being tested with realistic arc faults. He became convinced that the technology was effective.
One thing to be aware of, in Britian and most countries in Europe, residential occupancies have to have a residential current device (or RCD) on the mains as they come into the house. The RCD is a ground fault protection device, which trips at something like 30 mA (like the ground fault protection feature of the N. American AFCI breaker). No enough to protect against electrocution, but definitely enough to detect a high-impedance ground fault. That'll likely pick up a fault before it becomes a fire safety issue.
And back to the AFCI breaker requirments here in the States--yea, I've heard that the code-making panel that pushed the AFCI requirement is dominated by the breaker manufacturers. Maybe it's not just greed, maybe they deeply believe that universal use of AFCIs will prevent some fires and so save some lives.
All I can say is, If you're a hammer, everything looks like a nail.
Cheers,
Cliff
"I have seen some instances where an arcing fault occurred and it was a miracle that the house didn't burn down. Several cases of a receptacle with a loose wire at the poke-in backwire terminal, the receptacle melted to a greaer or lesser extent from the heat."That would be a series fault which the AFCI, until they came out with the combo versions, would not detect.I saw one video of a mockup where they had that kind of fault. And they clearly stated that it would not detect it. Now I don't remember if this part was stated or implied, but that after the insulation melted it might trip on a the ground fault. But by that time lots of damage has already been done and there could will be a fire by that time..
William the Geezer, the sequel to Billy the Kid - Shoe
Cliff,
Thanks for your input. That is one of most coherent presentation of arc fault I have read and I greatly appreciate your insight.
RegardsBruce
I am not really sure the reason but putting lights on an AFCI breaker can apparently cause accidental breaker trip. The municipal electrical inspector in my area told me that if I didn't want to have to worry about accidental tripping, I should have no lights on the AFCI circuit. Again, I am not an electrician, but hopefully the inspector at least knows what he's talking about. ADD: I would guess that if you vac plugged in downstairs trips your bedroom AFCI circuit, the only way that I know of that makes that possible is if they are in fact wired on the same circuit, or 2 separate circuits wired to the same breaker which would cause the type of overloading you are experiencing. When the vacum trips the breaker does the AFCI have to be reset? If not, then the breaker is most likely just being overloaded.
Edited 7/30/2009 9:17 pm ET by MDFContracting
"...should have no lights on the AFCI circuit."So, no wall lamps, no nightstand lamps, no reading in bed?Maybe you're supposed to run an extension cord from a non-AFCI outlet to your nightstand lamp?BruceT
Use candles instead. They're much safer.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
If your area has adopted the 2001 or new NEC or they amended the AFCI requirements the code requires all OUTLETS in bedrooms (and with the latest other rooms) to be AFCI protected.And as the NEC uses it an OUTLET is any place that electric is used. So that include lights, ceiling fans, wired smoke detectors, besides the receptacles..
William the Geezer, the sequel to Billy the Kid - Shoe
2008 ?
"2008 ?"No this is now 2009. And why would you be asking about the date in a forum. Easier to look at the calendar..
William the Geezer, the sequel to Billy the Kid - Shoe
Thank you (and to Hiker and the others), Just to clarify a couple of things. When the vac running on what ought to be a completely separate circuit trips the AFCI breaker it does not trip the breaker on the circuit it is nominally on. The AFCI does have to be reset after it trips in this manner, and it stays reset until the next time the vac is turned on.I should note that the rooms are essentially empty and apart from a few CF light bulbs the fridge, a few hand tools, and the vac there is no load at all. All the wiring and breakers are completely new, so there there is definitely something askew somewhere.
Electricity be funny...Is the breaker for the outlets that you have used for the vac on the same phase as the AFCI? If so, try moving one of the breakers to the opposite phase.AFCI's have built in GFCI capabilities and my limited info has it that they are just as sensitive to ground faults as a standard GFCI, so what you think is an arc sensing is really a GF.
So are you saying that the vac has a ground fault that the AFCI is picking up? I should be able to test that by plugging it into a GFCI outlet and turning it on, right?I have a very basic understanding of phases. Can I assume that one side of the panel box is one phase and the other side is the other phase? If that's the case I should try plugging the vac into an outlet in a circuit on the opposite side/phase of the box and see what happens.
There is a slight chance of some kind of cross neutrals or maybe a voltage drop problem although, off hand, I can figure out how a voltage drop problem would cause this.Try a high amperage resistive load. Heaters, toasters, irons.Get as much as you can on the circuit that you normally have the vac and see if it still trips. If so it is some kind of wiring problem.If not it sounds like the vac motor noise is getting back into the AFCI breaker.
.
William the Geezer, the sequel to Billy the Kid - Shoe
AFCIs are like panel-mounted GFCIs and have to be wired with the circuit neutral running through the breaker. Depending on the model, you will see two conductor locations on the breaker, one with a white dot or paint to denote the the branch circuit's white wire should be connected to it. Then there is a white pigtail wire that comes out and connects to the neutral buss bar.
Like a GFCI, and AFCI looks at what goes "up" the live/line and back "down" the neutral and compares them. That is why a ground/neural bridge is only evident when a load is applied.
I don't know if this is your problem but one more thing to check.
Andrew
"AFCI's have built in GFCI capabilities and my limited info has it that they are just as sensitive to ground faults as a standard GFCI, so what you think is an arc sensing is really a GF."There are combo GFCI/AFCI devices, but most are AFCI only.Now the AFCI do have ground fault detection that works much the same as GFCI, but it is set to trigger at 30 ma instead of 5 ma.The gf detection in AFCI is designed to protect againsts deteriating insulation and not personal safety like a GFCI.That said it would trip if there was a signicant leakage current to ground AND THE VAC WAS ON THE AFCI CIRCUIT, BUT IT IS NOT.Now if the neutrals of the 2 circuits are connected to gether (or the hots) then it could trip the AFCI from the normal current..
William the Geezer, the sequel to Billy the Kid - Shoe
Just a quick update. I plugged the vac into a GFCI outlet on a different circuit from the AFCI breaker. The vac ran fine and did not trip the GFCI outlet, but the AFCI breaker tripped.
Is it possible that the different circuit and the AFCI circuit have a shared neutral?
If the breaker is not malfunctioning, it's likely a shared neutral. Those are the dickens to find. Any switch, receptacle, or juncton box with two or more circuit in it could be the place where they cross.
Cliff
If it's a shared neutral it was probably wired that way from the panel. I don't know that you can be certain without removing the panel cover, but here are some clues:
1. The two circuits are on adjacent breakers.
2. Tracing the wires you find a 14/3 or 12/3 conductor cable heading back to the panel (black, red, white, ground).
3. You find a junction box common to both circuits, and inside red is twisted with black from another cable, or red is used as hot on some device.
Generally if it's a shared neutral, though, the breaker will refuse to reset even without a load on the circuits.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
I found this explanation. It might explain why a particular device, which when powered up, will, in the process of powering up, produce the arc signal that would be detected by the AFCI.
"Many loads are also powered by a common source. When an arc occurs on one branch of a source, it can drag down the voltage of that source in rapid succession, allowing an arc-like signal to be imposed on an adjacent circuit that shares that source."
This is true. Having other AFCIs on the same leg in the panel trip could occur when you run an appliance (such as a vacuum) which injects a lot of hash on the line. Anything with a brush-type motor is a good suspect for this.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz