Remote Relay Tripping AFCI

[jmottle]

I purchased a 30A remote relay to attach inline on an extension cord so I could remotely power a 15A/120V dust collector in my workshop. The issue is the device intermittently trips the mandatory AFCI breaker on this circuit.

The breaker is 20A and I have tried it on multiple circuits with the same breakers with the same result. When it trips the arc fault light appears on the breaker. The issue does not happen when connected to an older 15A circuit that does not have an AFCI breaker. (pre-code change) The AFCI circuits also do not trip if the dust collector is directly connected to any of the AFCI circuits, without the relay.

The manufacturer sent me a new one and the same thing happens. What's odd is that it's intermittent. I can turn it on 5 times and it works as expected and then 2 minutes later it will trip the breaker. Also worth noting is this extension cord has a light on it and they will work fine with no load attached and I can turn it off and on with the remote, triggering the light.

Does anyone have any suggestions or ideas here? The inputs on the relay are Live and Neutral IN and OUT. The grounds from the extension cord remain intact and are grounded to the box the relay is in.

This is the dust collector: https://www.busybeetools.com/products/dust-collector-1hp-570cfm-1-mic-bag-csa-ct053.html

This is the relay (code on the internal relay component is SRA-112DM: https://www.amazon.ca/gp/product/B07WV72DFR/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

[drussell]

Does it trigger the arc-fault right when it turns the relay on or off, or is it just random while it is running?

The arc-fault breakers will always sense at least some fraction of any kind of arc, including those that are expected, like a universal motor would create.  It may be as simple as just adding some suppression capacitance either across the relay contacts if that is that causes it or across the load side to suppress transients from motor I would guess...

Sometimes one breaker will become extra twitchy, if you have several you could try swapping them around and see if one is at least more tolerant if it remains an issue, I suppose...

[jmottle]

@drussell when it happens (which is 90% of the time) it's when the DC first starts up. Once it's running, I've never seen it trip. I have three brand new 20A AFCI on three different circuits and all three will intermittently trip. 

[fzabkar]

What happens if you convert the relay to SPST mode? That is, try connecting Neutral In to Neutral Out and then use the relay to switch the Active only.

[Gyro]

I'd go for some properly rated R-C snubbers across the relay contacts. If it's an indication that they are arcing significantly then it will improve contact life too.

[fordem]

What's the possibility/probability the arcing is in the dust collector?  What sort of motor does it have?

[jmottle]

What's the possibility/probability the arcing is in the dust collector?  What sort of motor does it have?

It's possible, but the dust collector on its own has never tripped the AFCI when directly connected to the circuit. It only happens when the relay is put inline.  I don't have a lot of info on the motor. Just the attached.

[jmottle]

I'd go for some properly rated R-C snubbers across the relay contacts. If it's an indication that they are arcing significantly then it will improve contact life too.

Would you have any advice on the sufficient snubber to use in a case like this?  My electronics experience is limited and I've had no experience with snubbers.

[Gyro]

I don't know what distributors you have available to you, but here's an example of what they are...

https://cpc.farnell.com/ampohm-wound-products/fe-sp-hdr23-100-100/contact-suppressor-0-1uf-100r/dp/FT00715

They are simply a Class-X safety rated capacitor and resistor in a single package, with insulated leads. You would simply wire one across the terminal block connections for each contact.