I have two Square D brand arcfault breakers that nuisance trip at seemingly random times, but always together. Both breakers are on the same phase, but otherwise have no connection.
The circuits are both bedroom outlet circuits, the master bedroom circuit has a lamp and clock on it and the other bedroom circuit has no load whatsoever as it is an empty guest room.
Both will be fine for two to four days and then I will discover that my alarm clock is off. I have never actually noticed the breaker tripping and can’t seem to duplicate the circumstances that caused it.
Any ideas other than a battery powered alarm clock or simply replacing the stupid $60 breakers with regular $6 non arc breakers?
Replies
Are those the only AFCIs in the house? Probably a switching transient coming in from the PoCo is at fault, or possibly a motor somewhere in the house.
SQ D had a recall on some.
Don't know the details the recall or why?
TRy googling to see if you can find the details.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
My first guess would be that the two circuits are connected together at some point.
All you can do is be methodical .....
1) Map every circuit, every device in the house;
2) Determine at what points the two cicuits are close to each other;
3) Start looking for cross-connections (including with the neutrals).
Just to eliminate the easy things, did you try putting them opposite phases in the panel?
Family.....They're always there when they need you.
Sue ... and he'll be able to find the interconnection by following the smoke, once he makes that into a 240v circuit by doing so!
Unlikely, unless both circuits are activated by resetting a single breaker (meaning the two are paralleled).It is vaguely possible that the neutrals are crossed, and moving one breaker to the opposite pole would prove this -- neither breaker would reset.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
Let's pause and look at this ....
He has two AFCI breakers that trip together.
Like a GFI, the arc fault breakers look at the neutral, as well as the hot wires. One possible cause of them both tripping is that some load is connected to the wrong neutral - that is, a neutral is "shared."
Depending on exactly where this connection is, part of that circuit could very well become exposed to 240v if one of the breakers is relocated to the other leg.
Small chance? That's a matter of speculation. So ... what would you choose: systemtic troubleshooting .... or willy-nilly switching wires around?
If you switch legs the neutral is still neutral.If the hots are cross-tied then the breakers will refuse to reset due to GFCI detection.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
SUre, sounds good, let's just make wild guesses and swap things around. Let me know when - not if- you let the smoke out.
OR .... do as I suggested ... and collect your DATA first. As in .... find out exactly what wires go where. Then kill the power and inspect the places where things come together.
If the problem seems to be somewhere in a particular section, you narrow that section down by methoically breaking it into ever-smaller sections, until you pinpoint the location.
AFCI circuits need to be kept completely apart to function properly. Period. The only way two AFCI circuits will trip at the same time is if they are somehow connected. That's the only way they'll both see a fault at the same time. Not by sitting in the wrong breaker slot, not from a factory defect, not by having a bad appliance.
Now, if the OP observes other details .... for example, the 'trip' happens when a particular switch is flipped .... then he has a pretty good clue where to start looking.
(Anyone who then thinks the switch is bad, and replaces the switch .... hang up your tool belt and get a real electrician out there - you're over your head.)
> The only way two AFCI circuits will trip at the same time is if they are somehow connected.Well, yes and no. Simply being connected to the same panel leg may be enough, if there's a transient coming through the panel. Or simply being side-by-side in the panel may be enough.And if a given AFCI design is susceptable to false trips caused by a particular type of transient, one would expect identical units to trip in synchrony when subjected to such a transient.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
I've seen a lot of criticism of AFCI's, but this claim of "transients" is new to me.
Can you document such issues having actually occured?
For that matter, any kind of 'transient' from the power company supply is a pretty rare occurance .... nearly all 'power quality' problems are created on the load side of the breaker.
No, have no documentation. But then I've never actually seen an AFCI, except in the store.But given how they must work (high frequency current waveform), they're certainly susceptable to transients on the supply side (though susceptability would also depend in part on the types of loads on the load side).
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
One thing about AFCI's is that they will trip if, say, the ground wire gets too close to a neutral screw as you push the device into the box. Other wiring 'errors' will also cause them to trip.
A common cause is when a circuit is connected to more than one neutral. This can easily happen when there is more than one circuit in a box, and often does happen when 3-way switch arrangements are involved.
We're back to the same thing that happened when GFCI's appeared: a lot of bad habits and sloppy work is getting caught. Some techniques, while certainly alloed by code, simply can't be used with these devices.
A lot of things have been asserted to cause AFCI problems; documenting them has proven to be a real challenge, though. I does seem that the most common cause of tripping is ... simply put ... human error.
That certainly appears to be the case here. One can imagine all manner of "maybe's," which is why it i important to get systematic. Stop guessing. Stop jumping to conclusions.
Start opening boxes and checking connections. I bet those two circuits share more than just the panel they're in ..... the two wires likely pass through several boxes together. All it takes is for one neutral wire to be landed uner the wrong wire nut, and both breakers will see a "fault."
Certainly the same wiring errors that can cause a GFCI problem are also a problem for AFCIs. It's not obvious that any new wiring-error failure modes are introduced, though.But it's unlikely that crossed neutrals are the issue here, since if they were connected then both breakers would refuse to reset.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
That's a lot of certainty over an unknown. Even though I'm no fan of AFCI's ... and lest my position have been 'lost in the fog' ... I'll restate it here:
1) There's nothing wrong with the power coming in;
2) There's nothing wron with the breakers;
3) There's nothing wrong with anything plugged in;
4) There IS a problem;
5) The problem is somewhere between the panel and the plugs; and,
6) The only way to find the problem is to methodically check things. This is basic trouble-shooting.
For those who have forgotten: basic troubleshooting comes in two forms:
A) Divide and conquor; and,
B) Start at one end and work to the other.
Let's just for the sake of discussion, assume there are four affected plugs: A,B,C, and D.
To "divide and conquor," you would remove A and B from the system, and see if the problem is still there. If it is, then its in C or D. If it's not, then it's in A or B. Pick the right pair, and try again.
Or, you can do the same, starting at one end of the circuit. Remove D ... does the problem remain? If so, remove C, Repeat until the problem goes away. The problem is in the last part you disconnected.
Now, you can't know where A,B,C and D are, unless you have made a map of what the circuits affect. Since homes are rarely completely documented, this means checking every outlet - receptacles as well as lights - to see just what is affected by the two circuits.
Then, you re-map each circuit individually. Comparing your maps, you ought to have a pretty good idea as to where the two circuits exist side-by-side. Since the fault affects both circuits, the problem has to be where the two are run together.
The most likely location is IN the common boxes ... in the connections, or the compression that happened when the devices were pushed into the boxes. It might even be an unused screw on the device sitting too close to a metal part of the box.
If everything looks OK in the boxes, yet you've located the problem as 'somewhere between C and D,' then you can megger test the wires to see if there is a problem with them.
You have to find the problem before you can fix it. It can be anything. Theory and guessing are fine - but they don't fix things. Only testing and measurement let you find the problem - and then you can fix it.
No assumptions, anymore. All we KNOW is that the fault affects two circuits. We have no idea what the fault may be. The fault has to lay within those two circuits. Now we have to find it. There is no easy way to do this. No shortcuts.
For someone who likes to "divide and conquer" you made a lot of unfounded assumptions going in.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
Step away from the panel. Unless you are right that the two circuit are interconnected (which you have no way of knowing), how is he gonna put 240 through the wires?
I've seen instances where there was a problem with the phases coming in to a house.
Family.....They're always there when they need you.
I conclude that the two circuits are connected, because:
A) The problem happens on only those two circuits; and,
B) Both breakers trip at the same time.
Mind you, the "gigo" principle applies. That is, I based my thoughts on the information I was presented. If there are no other AFCI breakers, then I cannot rule out a system wide problem ... at least, not in theory.
Mapping circuits ... the frst step I suggested .... would also make clear whether the circuits had anything in common at all.
That's the bonus of being methodical .... wild eyed theries and misunderstandings don't matter ... sooner or later you WILL find the problem .... and usually a lot quicker thn if oy continued to blunder from one guess to another.
Hey All-thanks for the input. a few points to clarify.The two circuits are completely separate, I wired the house and each bedroom has its own 20A Receptacle circuit. Wall switched lites and fans share a completely separate 15A AFCI circuit. Overkill, I know, I like to be able to isolate rooms. The two circuits do not cross and do not share any boxes. The cables even enter the panel on opposite sides. I have double checked the neutrals at the breakers and they are not crossed and are connected to the proper breakers. Both breakers are on the same "leg" ie: both on the same side of the panel with one other breaker in between them. There is one more AFCI on that same leg which does not trip with these two. Likewise the three AFCIs on the other leg have not tripped.Don't know if it matters, but this is a 100A sub-panel with separate neutral and ground bus bars as required.I have not been able to duplicate the conditions which trip the breakers, have not even noticed that they have tripped until later. The breakers re-set and hold without unplugging devices or making any changes to the circuits. I cannot even be absolutely certain that they trip simultaneously, only that BOTH are always tripped when I go to re-set. Have not had just one or the other trip in isolation.Minimal or no loads on the circuits when they trip. Guest room circuit has a lamp that has never been turned on at the time of a trip. Master has only an alarm clock and bedside lamp, both of which operate normally without tripping the breaker. No other switches or motor loads are on the circuits.It is the intermittent nature of the tripping which makes it frustrating. Divide and conquer, methodical isolation, and other standard troubleshooting techniques are rendered inconclusive as the problem is not constant. Will try swapping with two of the known "good" AFCI breakers to see if the problem migrates with the breakers or is a problem with the wiring/devices. Now I wish I hadn't clipped the pigtails so nice and neat.
Well, that's a start ... see if the problem moves when the breakers move.
More likely, you're missing some important bit of information ..... as in, someone isn't telling you when something stops working. For example, as they move about, vacuuming.
If the circuits are truly completely separate, then the problem tripping simply cannot be caused by the same event, at the same time. I can't imagine anything "before" the breaker, in the service, that would affect the breakers.
Perhaps .... plug an old-fashioned clock into each circuit, and see if they really do trip together?
Edited 10/21/2008 9:15 am ET by renosteinke
> I can't imagine anything "before" the breaker, in the service, that would affect the breakers.I can.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
Enlighten us Dan. I can imagine lots of things but I am having a hard time thinking of something that would only trip 2 AFCIs from the line side and leave the rest alone.
An arc on the line side. The AFCI can't really tell the difference between an arc on the line side and one on the load side.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
Note that one thing that could cause the appearance of an arc on the line side is a loose main lug on the panel. (Or, in this case, a loose connection at the main panel.)
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
The AFCI can't really tell the difference between an arc on the line side and one on the load side.
Actually, they can and do.
Maybe I missed you mentioning it.... did you check to see if your breakers are the aforementioned recalled breakers?
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
The square D recall was for AFCI breakers that didn't trip.
AFCIs look at current wave forms and there will not be any fault current through the breaker from a line side fault. Even if it would affect a breaker, why not all of them?
A line-side series fault could create the waveform the AFCI is looking for. A bad main lug connection, eg. Or nearby switching equipment might create the waveform.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
How can a fault on the line side of the breaker make current flow in the breaker? They look at current not voltage.
If there's any load on the breaker the current will flow.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
The orginal AFCI only detected parallel arcing. I think that it had to 60 or 80 amps.I believe that starting in 1/1/08 they where suppose to combination AFCI with would trip on on both parallel and series arcing.But I am not sure of the status of those and if they are bein shipped.Also I have not seen in info on the seeries mode."Possibly" and upstream arc could cause a breaker to trip in series mode. But I think that it would have to be drawing a signficant amount of current at the time.I am thinking *maybe* somekind of RF interferance, but I don't have a clue as to what kind.Remember the threads from about 3 years ago with a GFCI receptacel that kept tripping.Determined that it was from the cellphone that was being changed and the cellphone right next to the GFCI..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Even if it would affect a breaker, why not all of them?
The others have not failed YET! :-)
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
How many breakers of this identical design are on the same side of the 240V line?
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
You will need to ask the OP. I recall he said there are two "problem" breakers, on the same side of the box and also on the same phase leg.
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
Right, but I don't believe he ever said if there were any other AFCIs in the panel.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
In post #22 http://forums.taunton.com/tp-breaktime/messages?msg=111574.22
he says
"Both breakers are on the same "leg" ie: both on the same side of the panel with one other breaker in between them. There is one more AFCI on that same leg which does not trip with these two. Likewise the three AFCIs on the other leg have not tripped."
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
OK, I didn't catch that. There would still be the question of whether all the AFCI breakers are of the same brand and design (and possibly lot number).Aside from that, in order to trip due to a supply-side transient I believe there would have to be some load on the breaker -- something like a single lightbulb, or possibly even a "wall wart".It would not be unexpected that breakers on only one side would be hit.
Corporation: n. An ingenious device for obtaining individual profit without individual responsibility. --Ambrose Bierce
I don't think that it makes much of a difference with a single phase service, but try putting the arc faults on different phases (legs). You may just have a load balance issue.
I have two Square D brand arcfault breakers that nuisance trip at seemingly random times, but always together.
Have you determined that an arc fault is not present? How?
One obvious cause of the problem would be that the AFCIs are (correctly) detecting a fault. Seems unlikely that two would trip at the same time, though, but I guess it's possible.
I just find it often works better to rule out the simple stuff first.
How bout leaving the unused circuit off for a few days and see what happens?
Joe H
I had this problem once and it ended up being the neutrals were reversed. I swapped breakers with ones that were working, I replaced the breakers with new ones and finally I pulled the wires in the panel for both breakers and found I did have the neutrals reversed. If you want to try and cause them to trip, plug in a vacuum cleaner.