Air Conditioner Tripping Breaker

[DieselDennis]

Preview to the thread. I bought a new to me house last July. So we've been living there just over a year, but we'll call it two summers. The house was built in 2000. The previous owner stated on the paperwork that the compressor in the outside AC unit was replaced in 2013. I, and my AC man have verified that the compressor looks like a 2013 vintage.

I have a 40 amp (double) breaker coming off of the meter dedicated to the outside unit. One time, early in the summer (sometime in May?), LOML tells me that the AC is blowing hot air. Astutely notes that she doesn't hear the outside unit running. I go check the breaker and it's tripped. So I flip it back on. Unit purrs to life and blows cold.

Fast forward to last weekend. We were gone on a trip and I set the thermostat to 80 before we left. Came back home Sunday night and find the house is 87. The air handler is blowing it's heart out, but the outside unit is not on. Check the breaker first thing. It's tripped. Flipped it back on. Fired to life and blew cool air.

So yesterday I decided to do some investigation. I put my amp clamp on each wire going to the unit. I was getting 27-28 amps at start up, leveling off to 22-24 amps steady. Shouldn't be anywhere near enough to trip a 40 amp breaker. My question is, why the randomness? The starter capacitor looked original to the unit. The contactor looked newer.

I sure don't want to go spending money for the heck of it. On the other hand, being proactive often comes out a little cheaper. And it's going to be at least 102 for three straight days this weekend.

Why's the breaker tripping at random? Would you do anything about it?

[CLETUS]

DieselDennis said:

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Why's the breaker tripping at random? Would you do anything about it?

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Did you check for any loose wires?

That was my issue last year.

[daveferg]

My blower was protected with two in-line fuses which also would blow similar to what you're describing----I put in slow-blow fuses, which sort of solved the problem. When I would lose the full function was when the AC had been running a while and shut off and then try to start again. One AC tech told me you should let the unit sit idle for a while to allow that liquid freon would settle back to wherever it was stored.

The tech also added some gizmo to the start circuit (capacitor??) but said it was only a stop gap and eventually things would get bad enough the entire AC would need replacing.

On yours, if just the fan/condenser unit was replaced---maybe there's something wrong with the rest of the system.

All I can tell you is we bit the bullet like 10 years ago and replace the AC-----and haven't had a problem since then.

[daddo]

Loose wire/connection at breaker.
Weak breaker- breaker overheating.
Bad start capacitor or start relay (Start assist).
Voltage problem to the compressor.
Small internal short in the compressor.
Bad/weak winding in the compressor.
System grossly overcharged.
If it is a piston compressor- bad crankcase heater.

To name a few.

Already lost one compressor. Perhaps the reason for the first failure still exists.

I'd replace the start assist and check if the crankcase heater is working if needed, check the breaker and connections- and start there.

[Robert Adams]

That's pretty high running amp draw. A newer 4 ton will pull around 17 depending on seer load temps etc... I'd also be looking to see if it's way overcharged. But I also wonder if the compressor is too big for the system or the orifice, flow rate or expansion valve is plugged some putting more load on the compressor.

Also check the amp draw on the condenser fan and make sure the start capacitor is good and the correct capacitance as if it's way off it can increase amp draw.

[daddo]

Robert Adams said:

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That's pretty high running amp draw. A newer 4 ton will pull around 17 depending on seer load temps etc... I'd also be looking to see if it's way overcharged. But I also wonder if the compressor is too big for the system or the orifice, flow rate or expansion valve is plugged some putting more load on the compressor.

Also check the amp draw on the condenser fan and make sure the start capacitor is good and the correct capacitance as if it's way off it can increase amp draw.

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I was thinking the amp draw seemed high too- could be he just had a big load at those ID and OD temps.

[Robert Adams]

I think you were right daddo that the issue that toasted the old compressor is still there. I'm still thinking a restriction at the txv or flowrater making the compressor work harder and overtime is causing damage to the compressor.

A thought too. He said the voltage was good but was that voltage tested under load or not? I like to check both.

[AlanBienlein]

Is the breaker "HACR" heating, air-conditioning and refrigerator breaker rated?

[DieselDennis]

More testing this evening.

Incoming voltage is 248V. A little high, but that should help with the amperage.

I tested the capacitor. It's a 5/55 uf capacitor. It tested 5 & 52. It actually started out at 51.7 and climbed to 52 uf. So while it may be within 6%, it's on the fringe.

I'm not sure if the breaker is HACR rated. It looks like a std two pole 40 amp breaker, except it's lug mount instead of rail mount.

[AlanBienlein]

DieselDennis said:

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More testing this evening.

Incoming voltage is 248V. A little high, but that should help with the amperage.

I tested the capacitor. It's a 5/55 uf capacitor. It tested 5 & 52. It actually started out at 51.7 and climbed to 52 uf. So while it may be within 6%, it's on the fringe.

I'm not sure if the breaker is HACR rated. It looks like a std two pole 40 amp breaker, except it's lug mount instead of rail mount.

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It will say it on the side. There is the possibilty the breaker is just getting weak.