Miter saw causes AFCI trip on Schneider XW but not on grid

[hwy17]

Just an interesting note here, not really something I will try to track down. I have another standard thermal magnetic breaker circuit I will use for the miter instead.

I have not had any nuisance trips with my Homeline GFCI/CAFCI breakers until now. At least combined with the other mix of loads I had going yesterday, starting my miter saw was tripping the breaker for arc fault detection (as determined by the breaker's "last trip" diagnostic method).

I guess the way the XW was responding to that load was setting off the AFCI. It's a serious load, 10" blade I think and probably 30-70 inrush amps. But it never did this on grid power.

I'm just glad that it didn't go and set off every AFCI in the house, as it seems like they would all be hearing the same noise on the output of the inverter.

This is running off the inverter purely, no grid AC input at all.

The first time it did it, I thought I'd tripped the inverter overload. I'm trying to go for a 3 month uptime without any interruption for maintenance or any reason, so luckily my streak remains intact.

 

[DIYrich]

Might be the Inverter (not pure sine wave) plus worn brushes create an irregular rhythm that the breaker detects as an Arc Fault.

Brian Millman Electric - Why Your Arc Fault Breaker Keeps Tripping

Brian Millman Electric We Offer a Wide Variety of Electrical Services at an Affordable Price

www.brianmillmanelectric.com

"... motors, like the ones found in the power drill, vacuums and treadmills produce a rhythmic, mechanical arc pattern. So they program these patterns into the digital “brains” of the AFCI breaker so it won’t trip as often on these common household items."

"This is because the brushes wear down on these older motors, which causes the arc pattern to become irregular and not as rhythmic as when the motor was new."

 

[hogback]

Not sine wave?

 

[hogback]

I start my 10" miter all the time on xw+. But.... no afci breakers. Yet. Am planning on redoing my main panel, qo, with afci where it might help. Am planning on keeping some standard breakers around. The house wiring is sup par as we inherited it. Small place, so not too much work to rewire everything. Thinking the afcis might just trip instantly. Heard that afci is better these days, but I have zero experience. How old are the homelines?

 

[DIYrich]

Not sine wave?

Not "pure". Inverters simulate sine wave with steps. The more steps, the better. However, they are still steps. AFCI is probably expecting pure sine wave, and looking for anomalies. Simulated sine wave with worn brushes may be just enough to cause problems. The link said that even with grid power (pure sine wave) worn brushes could cause problems with AFCI. Could be worn brushes good enough for grid, but not good enough for simulated sine wave.

 

[hwy17]

Thinking the afcis might just trip instantly. Heard that afci is better these days, but I have zero experience. How old are the homelines?

Homelines are 1.5 years old and otherwise have been great, no nuisance AFCI trips on our old mix of 40's, 50's, and 80's wiring inside.

I'll just use the other non AFCI I added now for the miter saw from now on.

 

[400bird]

It's the motor, afci doesn't get along well with motors. Especially brushed motors.
But, my washing machine has a brushless motor with speed controller built into the electronics, any AFCI refuses hold against the washer.

I just ran off grid through that solar storm, while the AC was running I was out in the garage with the air compressor and 10" table saw going, no issues.

 

[hwy17]

It's the motor, afci doesn't get along well with motors. Especially brushed motors.
But, my washing machine has a brushless motor with speed controller built into the electronics, any AFCI refuses hold against the washer.

Yeah, the curious part to me though is that the inverter is a factor. Same AFCI breaker is fine with that miter saw on grid power.

 

[hogback]

Maybe you need a better quality inverter?

 

[hwy17]

Maybe you need a better quality inverter?

Nobody better dare question an XW! It's big iron!

 

[wheelman55]

Same issue here with XW+ and the combi AFCI breakers. I changed out the breakers where I run tools to GFCI only and this works well so far.

Some tools trip the combo breakers and some don’t.

I had another interesting trip using my Dewalt miter saw on a circuit that I’ve used to make hundreds of cuts. Also protected by one of the AFCI combo breakers.

I tracked that down to having the charger for my Specialized E Mtb plugged into the same circuit. The bike battery was not connected to the charger.

As soon as I unplugged the charger the saw worked as it always has.

Best of luck. You’ll figure it out.

 

[hwy17]

I tracked that down to having the charger for my Specialized E Mtb plugged into the same circuit. The bike battery was not connected to the charger.

Ooh my Makita charger is on that one too!