AC Compressor causes Arc Fault breaker on another circuit to trip

[aftershock]

AC circuit is in a sub panel which is fed from the main panel where the arc fault circuit is.
Sub panel fed with a neutral and also has an arc fault circuit which does not trip.
The AC has an issue which when the contactor kicks in, it trips the 2 pole breaker that controls it, and also causes the arc fault in the main panel to trip.

Eaton brand.

 

[Little Bill]

AC circuit is in a sub panel which is fed from the main panel where the arc fault circuit is.
Sub panel fed with a neutral and also has an arc fault circuit which does not trip.
The AC has an issue which when the contactor kicks in, it trips the 2 pole breaker that controls it, and also causes the arc fault in the main panel to trip.

Eaton brand.

What is on the circuit that is fed from the tripping AFCI? Does the AC unit need a neutral for anything? Maybe a condensate pump or other things that may require a neutral?

Also sounds like either the breaker for the compressor is undersized or something is wrong with the compressor.

 

[mopowr steve]

AC circuit is in a sub panel which is fed from the main panel where the arc fault circuit is.
Sub panel fed with a neutral and also has an arc fault circuit which does not trip.
The AC has an issue which when the contactor kicks in, it trips the 2 pole breaker that controls it, and also causes the arc fault in the main panel to trip.

Eaton brand.

I have found that when an appliance which either truly has an arcing event or simulates an random arcing event can at times cause arc fault breakers to trip which are not related to the circuit in question. ( I found this out after extensive troubleshooting a new home where it was their flat screen tv had a defective power supply sending a simulated arc signature on the entire electrical system causing random tripping of arc fault breakers thru-out the panel.) Back to my response, I wonder if the contactor in you AC has bad contacts and is causing excessive arcing? If this is so the double pole breaker feeding the AC is under erratic/excessive currents and possibly tripping because of that.

 

[templdl]

AC circuit is in a sub panel which is fed from the main panel where the arc fault circuit is.
Sub panel fed with a neutral and also has an arc fault circuit which does not trip.
The AC has an issue which when the contactor kicks in, it trips the 2 pole breaker that controls it, and also causes the arc fault in the main panel to trip.

Eaton brand.

Yes, my concern first is to why the 2p beaker tripped. As often happens with questions and concerns we're left to do a lot of guessing. You weren't clear about the AFCI breaker. I'll tale a wild guess that it is a 1p 15 or 20AT AFCI breaker which feeds an entirely different circuit.
But, back to the 2p breaker. I would be extremely concerned about what is causing it to trip and that the AFCI is just a side collateral issue which shouldn't be happening. It may be a symptom as to what is causing the 2p breaker though.
Should you solve the cause of the 2p breaker tripping the AFCI breaker issue will go away and as such don?t let that bother you? If you a curious and have the time I would go look closely for neutral and ground issues That cold fool the FCI into tripping because of what ever is causing the 2P breaker to trip.

 

[cadpoint]

Well, I have more statements than answers.

I have a split system, gas pack inside, fan and air compressor is outside, I'll asume yours is the same.

I just turned on my A/C this Week! The Kids are home!

Buy a new contactor(period).

I fired mine up and noted it was letting smoke out(outdoor unit), it lasted two days. Replaced that and one of two capicatiors... total 14 Dollars.

I also noted and replaced one wire to the compressor that had a bad end and replaced many other female ends, frankly I think I'll just rewire the whole machine when the weather breaks...

Here's what I'd look for! Make sure your low voltage transformer is supplied from the same panel, not that that matters but it should not shared with or on the doorbell trannie. That the L. V. transformer is not on a AFCI circuit, but get it power cleanly, or from the Heater circuit.

My thoughts are that the transformer is supplied from a of AFCI powered circuit ! (?)

With the contractor pulling in, running off of a bad/worn contacts, combined bad female connectors, who know where the transformer power is supplied, all bets are off!

Check / tug on all connectors and inspect wires, replace accordingly.

I've replaced the contactor twice in ~ 10 years.

The unit is ~ + 30 years old! Yes I nurse it to life, and I think it needs a freon charge !

 

[suemarkp]

Is one of the wires on the tripping AFCI circuit next to the feeder containing the compressor? Wondering if the big surge is inductively coupling to the protected side of the AFCI circuit. That extra current could look like an arc or trip its GFCI section if it is up to 30mA.

 

[kwired]

Well, I have more statements than answers.

I have a split system, gas pack inside, fan and air compressor is outside, I'll asume yours is the same.

I just turned on my A/C this Week! The Kids are home!

Buy a new contactor(period).

I fired mine up and noted it was letting smoke out(outdoor unit), it lasted two days. Replaced that and one of two capicatiors... total 14 Dollars.

I also noted and replaced one wire to the compressor that had a bad end and replaced many other female ends, frankly I think I'll just rewire the whole machine when the weather breaks...

Here's what I'd look for! Make sure your low voltage transformer is supplied from the same panel, not that that matters but it should not shared with or on the doorbell trannie. That the L. V. transformer is not on a AFCI circuit, but get it power cleanly, or from the Heater circuit.

My thoughts are that the transformer is supplied from a of AFCI powered circuit ! (?)

With the contractor pulling in, running off of a bad/worn contacts, combined bad female connectors, who know where the transformer power is supplied, all bets are off!

Check / tug on all connectors and inspect wires, replace accordingly.

I've replaced the contactor twice in ~ 10 years.

The unit is ~ + 30 years old! Yes I nurse it to life, and I think it needs a freon charge !

Based on your response I think you are suggesting the 24 volt control circuit is involved in the AFCI tripping, wouldn't you think it is more likely that the compressor circuit is involved in the tripping of the AFCI?

aftershock - there has been similar discussion here at times involving inductive kickback and GFCI's. It may be worth looking into this as possibile source of your problem. Search this forum for "inductive kickback" as well as the word "snubber" and you may get some ideas worth at least looking into a little deeper.

 

[aftershock]

I did a search for this type of issue on this forum and found a few threads on it before I made this thread.
This house in question is one I rewired about 6 years ago.

1. The AFCI is 15 amps and controls a light circuit on the 2nd floor
2. The sub panel for the CAC compressors (House has 3) also has a neutral because I have other circuits coming from this sub panel including 1 20 amp AFCI (which does not trip)
2 The breaker for the sub panel is 3 or 4 slots down from the 15 amp AFCI in question. I don't know if the neutrals are close to each other on the bar, I did not remove the panel lid.
3. The CAC unit in question was just worked on a week prior because of HVAC related issues. Apparently it still has issues since it causes the 60 amp breaker to trip every time the unit attempts to engage. The breaker is sized per nameplate and I even changed the breaker to make sure I did not have a weak one.
4. According to my marking on the panel, the air handlers are in the other main panel (house has 2 200 amp main panels).

 

[aftershock]

Is one of the wires on the tripping AFCI circuit next to the feeder containing the compressor? Wondering if the big surge is inductively coupling to the protected side of the AFCI circuit. That extra current could look like an arc or trip its GFCI section if it is up to 30mA.

I was not aware that AFCI's also had GFCI protection as well.

 

[aftershock]

Should you solve the cause of the 2p breaker tripping the AFCI breaker issue will go away and as such don?t let that bother you? If you a curious and have the time I would go look closely for neutral and ground issues That cold fool the FCI into tripping because of what ever is causing the 2P breaker to trip.

I am curious and will be looking into this further next week.

 

[cadpoint]

Based on your response I think you are suggesting the 24 volt control circuit is involved in the AFCI tripping, wouldn't you think it is more likely that the compressor circuit is involved in the tripping of the AFCI?

Yes

If a contactor fails is it only limited to faulting the A/C circuit, when another path is available? Design wise no, possible, yes. What I didn't say was that ten years ago, I replaced the low voltage wire and a transformer when I replaced the first burnt contactor. It smoked everything!

Mine was just a story to throw out ideas and explain things. I assumed a lot to make any comparisons to their structure verse mine.

In the case of the OP, fine they need a contactor. They need to understand a lot more and gainable by your posting links.

They might need to meggar the circuit, they'd be silly not to if the ends are chalky or if oxided or if the 240 circuit wire is breaking down.

 

[hillbilly1]

I don't know if this service has a main disconnect outside, but something worth looking into is if the bond screw is installed there. I don't know exactly what the afci is looking at, but a high resistance ground could cause the arcing signature if a fault is applied. Electronics are kinda funky that way.

 

[kwired]

Yes

If a contactor fails is it only limited to faulting the A/C circuit, when another path is available? Design wise no, possible, yes. What I didn't say was that ten years ago, I replaced the low voltage wire and a transformer when I replaced the first burnt contactor. It smoked everything!

Mine was just a story to throw out ideas and explain things. I assumed a lot to make any comparisons to their structure verse mine.

In the case of the OP, fine they need a contactor. They need to understand a lot more and gainable by your posting links.

They might need to meggar the circuit, they'd be silly not to if the ends are chalky or if oxided or if the 240 circuit wire is breaking down.

Still not sure I follow what you are saying. I'm trying to say that a fault or any other failure of the separately derived 24 volt contol circuit is going to have any effect on a AFCI protected branch circuit on another system. If there is crossover connection between the two systems then we have a different problem, but the energy involved in causing the AFCI to trip is probably still coming from the 120 volt source and the 24 volt ciruit is just another impedance unexpectedly introduced into the circuit.