Unit tripping breaker

[Bseliger]

I have a Ruud unit that was tripping a 30 amp breaker every two to three hours. The unit was running with 0 superheat and upon initial start up would sen 70 amps to the compressor and quickly jump down to 12.9 amps and operate normally. When I pulled the disconnect and let my pressures kinda equalize to 100 on the suction and 115 on the discharge the unit would pull 120 amps and trip the breaker. The compressor was LRA at 104 and suppose to run around 17. The capacitor checked good on both sides. Model UAPC-048JA2 serial 6994M250708930 R-22. I did charge the unit some, didn't want to dump 22 in a unit that may have a bad compressor, which is what I feel it is. After letting the unit sit for a good 5 mins the unit will start up normally again. Im afraid too many time of 120 amps has taken its toll. We are the third company there and the compressor is still in warranty. Any Ideas guys? 115 discharge 60 suction and ambient outside 80, inside I believe was 70 ish. All of the pressure are from my memory

[HvacBry]

Compressor shorting to ground?

Did you OHM out the compressor by chance?

I had one the other day that tripped the breaker before I arrived, I ohmed it out, and it had shorted to ground. new compressor on the way.

[Core_d]

Low charge would not open a breaker. I would say compressor as well.

[Bseliger]

I did not ohm the compressor. The only time the unit trips the breaker is upon restart of the compressor after everything is close to equalizing. Unit is from 2007, and is a 14 seer unit. Home owner purchased the house half way built because orginal builder went bankrupt and the unit was in when they purchased. I hate telling someone a six year old compressor is bad, but I have no idea what the previous guy did on install, maybe he never got paid and said eff it. The parts house said normally scroll compressors don't fail, but if theres a bunch of crap in there who knows. Pressure's did stay fairly steady though.

[Poodle Head Mikey]

What is the voltage at the compressor terminals when it was trying to start? Because unless you know that - then you don't know anything.

After you make sure the voltage is correct While The Compressor Is Starting - then why not install a large hard start kit and then Make Sure the proper charge is in the system?

I think you will find that the system is overcharged. Even more since you've been there. <g> Although that's just my 'way over here' guess. <g>

PHM
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I have a Ruud unit that was tripping a 30 amp breaker every two to three hours. The unit was running with 0 superheat and upon initial start up would sen 70 amps to the compressor and quickly jump down to 12.9 amps and operate normally. When I pulled the disconnect and let my pressures kinda equalize to 100 on the suction and 115 on the discharge the unit would pull 120 amps and trip the breaker. The compressor was LRA at 104 and suppose to run around 17. The capacitor checked good on both sides. Model UAPC-048JA2 serial 6994M250708930 R-22. I did charge the unit some, didn't want to dump 22 in a unit that may have a bad compressor, which is what I feel it is. After letting the unit sit for a good 5 mins the unit will start up normally again. Im afraid too many time of 120 amps has taken its toll. We are the third company there and the compressor is still in warranty. Any Ideas guys? 115 discharge 60 suction and ambient outside 80, inside I believe was 70 ish. All of the pressure are from my memory

[Bseliger]

While I did not check the voltage at the compressor and you are right I should have.... If the compressor will run for 20 mins and then shut down when the house is satisfied, but will have problems restarting I guess I assumed that side of the equation was good. Also my amp draws I felt were good at 12.9, wouldn't that also give me a high amp draw through out the cycle just not on start up?

[frank slusher]

Most compressors will draw locked rotor amps on a rapid restart, 5 min time delay would allow good equalization of pressures.

[Poodle Head Mikey]

Your mention of zero SSH piqued my interest.

Amp draw is not much affected by charge until the variance is massive.

All compressors should have a hard start kit installed - it's the best thing you can do for them. And here is one that doesn't like to start for some reason - so it seems even More of a likely candidate.

But on a hard to start / fails to start job - always check the voltage at the compressor terminals While It Is Trying To Start.

Also: Never Assume - Always Verify what you think or suspect. If your boss doesn't like the extra minutes it takes - then you have the wrong boss. So either force the issue and do the right thing for yourself - or get a new boss.

PHM
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While I did not check the voltage at the compressor and you are right I should have.... If the compressor will run for 20 mins and then shut down when the house is satisfied, but will have problems restarting I guess I assumed that side of the equation was good. Also my amp draws I felt were good at 12.9, wouldn't that also give me a high amp draw through out the cycle just not on start up?

[Back Bay Basser]

What's that superheat for anyway? Got nothing to do compressor protection does it?

[ryan1088]

Also: Never Assume - Always Verify what you think or suspect. If your boss doesn't like the extra minutes it takes - then you have the wrong boss. So either force the issue and do the right thing for yourself - or get a new boss.

PHM
------

I like this paragraph, very well said.

I always say if you didn't have time to do it the first time, what makes you think we have time to do it again the second time? Little things get missed because we hurry.

[Bseliger]

Ive never heard anything about time from my employer, like I said before I should have checked it but elected not too. The question was also missed.... if the unit runs for twenty mins, its not voltage. The only time the unit trips the breaker is on restart and the unit has to sit for a good 5 mins. Time delay relay did cross my mind, but the fact that these people bought the house from foreclosure and have had this issue for quite some time makes me wonder about the condition of the windings on the compressor.

[Bseliger]

The reason I come on this forum and ask these questions is because im curious if and how ive made a mistake and want to learn from people that have more knowledge in the field than I do... I take pride in offering good workmanship and trying to get people what they pay for. Im quick to accept responsibility for things that I have or have not done correctly so lets leave all the extra curricular stuff to the side

[mgenius33]

Ok, from the little information that was given:
Low superheat
Possible Low suction
Low head
Likely compressor slugging

Possible causes, oversized metering device with low charge, and or low airflow.
If the system runs fine, I don't see replacing a compressor on a guess.

[Bseliger]

I went back through things in my mind, The suction was 75 and the head was around 150. I realize now I added refrig to an already overcharged system with 0 superheat.... 75 psi = 40 f, and my suction was around 40-41 f.

[Back Bay Basser]

There are way too many numbers in this business to "I went back through things in my mind". I always have pad and pen available, it helps me to think things through to logical conclusions. Then again not everyone is slow as I am so some probably don't need notes.

[mgenius33]

Sounds like stuck open TXV, or oversized metering device. Someone likely dumped some charge to reduce superheat, and compressor noise.

[Bseliger]

That's totally fair, I have no problems with that. This is the first time I've seen something like this and I should have taken better notes.

There are way too many numbers in this business to "I went back through things in my mind". I always have pad and pen available, it helps me to think things through to logical conclusions. Then again not everyone is slow as I am so some probably don't need notes.

[ryan1088]

Sounds like stuck open TXV, or oversized metering device. Someone likely dumped some charge to reduce superheat, and compressor noise.

I never saw where he said that it was a txv.

Is this a txv or fixed???

[Bseliger]

The unit was a txv, the whole scenario was bothering me so I went back over to the homeowners house to take some additional information. I megged the compressor and both run and start windings were bad. Voltage was good at 240. I installed a time delay relay and set it for 10 mins so the unit hopefully wont trip on them in the middle of the night. Will order a new compressor in the mourning

[smokeater2025]

scroll or hermedic compressor? piston or TXV? if txv with herm then you need hard start to overcome pressure diff.