I have a problem with AFCI breakers tripping in my 2 and a half year old house. The builder's electrician said that the cause is from power surges coming from the electrical company and that I need to get a surge protector put in at the service.

The breakers are Sqaure-D QO120 single pole plug on neutral. When the trip its about 7 or 8 of them the frig, microwave, dryer, some plugs when the laptop is plugged. This usually happens when it's raining or damp out.


5 Answers 5


The job of AFCI is to protect the house from series or shorting arc faults, which cause fires.

The main reason AFCI breakers are required today is because so many houses are built with backstab connections to switches and receptacles, and those so often fail in a series arc fault mode.

Keep in mind, the builder's electrician is the one who wired the place. So the last thing he's going to say is "it's tripping because I used backstab connections when wiring your house because I was in a hurry, and one is failing as they often do. Sure, I'll do a go-back and spend two hours taking apart all your receptacles and moving the wires to the screws, or fitting the $3 receptacle instead of the 60 cent one".

That said, it can also be a failing appliance. However if you move the appliance to a different AFCI protected circuit, this circuit will stop tripping and that circuit will start.


As mentioned all appliances, TV's, computers, LED Lighting, Dishwashers, etc.(pretty much everything we use except a toaster or incandescent light bulb) have a device whether it be a switch mode power supply, pulse width moudlator, rectifier, etc. that changes the AC input to DC outputs to power and control stated devices. Any switching action creates what are called harmonics on to the circuit. To over simplify harmonics aka noise, it is an induced current and voltage on the circuit. Specifically the odd harmonic orders are additive meaning that they do not cancel and "add" current and voltage to the circuit which can trick the AFCI into thinking there's a fault and therefore opening the circuit. Sometimes a surge protection device can be added in series to the circuit meaning adding a plug in SPD to the outlet and plugging in the appliance to that. The theory is a SPD will "absorb" the induced voltage caused by the switch mode power supply, i.e. harmonics, and therefore limit the induced current as well there by not "looking" like a fault to the AFCI thus allowing the CB to remain closed. The reasoning being that per ohms law as long as you have a constant resistance in the circuit then the Voltage is proportional to the current and vice versa. So higher voltage equals higher current. The problem with a SPD ahead of the panelboard is that it may not "absorb" the smaller voltage on a single circuit enough to keep the AFCI closed. The SPD at the panelboards function is to protect from upstream overvoltages not so much as down stream and is thus recommended to have an SPD in series on the circuit as a potential solution to AFCI nuisance tripping.

Try to make this theory/suggestion as simple as possible without getting into the mathmatics too much. And yes we have had success with adding an SPD in series to a nuisance circuit. And also we have not had success as well though not as much. Good luck everyone


First installing a whole house surge protector is never a bad idea, but I wouldn't put much faith that it will cure your "nuisance tripping" of AFCI's. My reasoning is that a circuit AFCI device protects from arcs downstream of its installation.

Nuisance tripping is caused by some appliance, device or fixture arcing internally. Try and identify which circuits are tripping. Then survey which appliances, and device are on those circuits. You can test an appliance by disconnecting them from a circuit and see if they do the same thing on a different circuit. Now you have isolated the problem to either an appliance or the circuit itself. If it is an appliance the only thing you can do is replace the appliance, if it has a warranty you might get it replaced for free. If it is the circuit it is probably a switch, light fixture or arcing internal to the circuit. You might be able to get that fixed under the general contractors warranty.

I am not saying that external power surges will not cause tripping but it would be a pretty noticeable event. First you would get a flickering or dimming or surging then your AFCI devices would trip.

So try and focus on the event of the tripping and make a logical deduction of the cause. Also try and get a second opinion once you have better information about the cause.

Hope this helps. Good luck.


First off, a whole-home surge protector is almost certainly NOT going to solve your problem.

I've had issues with my AFCI breakers tripping with large motor appliances (i.e. electric lawnmower, electric snow-thrower, mitre saw). This was in a brand-new build, so I was able to call them on it as a "warranty" issue.

The electrician came and swapped several of the AFCI breakers -- when the house was built a year ago, it was the first generation of AFCI that got installed. A few were updated to third-generation about 6 months ago, and there's now a fourth generation that I had them replace the rest with.

The third-generation AFCI, coupled with a decent surge suppressor power bar for the device seems to have eliminated the nuisance tripping. I haven't played with it to see if the power bar is still needed, but between those two things, the issue is resolved.

As for the "cause" of the AFCI being required now... that's up in the air. This is the first time I've heard of the blame being on the backstab connectors. Most seem to blame the idea that folks don't take care as to where they place nails and screws and a drywaller or homeowner ends up putting one right through the electrical wiring in the wall. The alternative theory (which is perhaps closer) is that it has to do with poor maintenance of device power cords.

I tend to believe it's the latter since our current code only required AFCI for (some) outlets and it excluded switch / lighting circuits and others like fridge and washing machine.


There are known issues with some types of devices causing nuisance tripping of AFCIs. A big culprit is LED drivers (the driver is the power supply that is used on LED lamps). All of them are made in China and not all of them have the same quality controls as others, so there are a LOT of them out there that create high levels of what's called "common mode noise" on an electrical system. All electronics produce this, but AFCIs have been designed to discriminate it from "real" arc faults, when the power supply is properly designed and tested to regulatory standards. However that's where the QC problem comes in, because many of the lower cost (and some not so low) LED drivers are emitting high frequency CM noise that IS tricking the AFCI sensors by having a "signature" similar to that of an electrical arc. Whirlpool had a major recall of their refrigerators a couple of years ago because an LED driver on the stupid little display on the door was causing AFCIs to nuisance trip. Samsung has had a more recent similar recall. We hear about those because a tripped AFCI on a refrigerator is a potential health hazard, not just an inconvenience. But LED lamps and fixtures are doing it too.

Surge arrestors are not going to do anything for that. I'm going to experiment with ferrite cores the next time I have this problem. I don't know if it will work, but they are a cheap experiment.

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