Any ideas????????????

[wuffdog]

Put in a new 2 1/2 ton Heil condensing unit several weeks ago. Unit has run fine until this weekend. Thermostat calls for cooling, unit starts up and runs fine. Cools house well. When the thermostat is satisified the unit shuts off until the next call. When the thermostat calls again the circuit breaker trips. Let it set for 1 hour and then it will come on and run fine.Once the thermostat is satisified and shuts down, then tries to start again, the breaker trips. FLA @ 10.2, LRA @ 225 (max for unit startup is 255amps). When system shuts off pressures equalize at 118 psig. Operating pressures today at ODT 80, IDT (DB) 73 L/S 72psig, H/S 195 psig, SH is 17 degrees. Condensing unit mounted 30 from furnace. Checked windings no shorts or grounds. No exposed wiring.Brand new breakers. Unit rated max breaker at 30 amps. All brand new wiring throughout the house. This was a remodle job for one of our customers. Thought maybe the compressor was having a hard time starting, tried adding a hard start, but to no avail it still trips. Contacted manufacturer rep. He is clueless.You can't even get an amp reading on start up cause the breaker trips. Any ideas?????????????

[hal parker]

Did you install crankcase heater? Might be liquid ref migrating to comp.

[davidr]

Have you tried isolating components to see if it is the compressor or the fan motor?
If you can find someone who has a fluke 87 it may be quick enough in the recording mode to catch the inrush current before it trips the breaker.
Is there a possibility the problem may be in the run capacitor?

[Mr Bill]

Originally posted by wuffdog
LRA @ 225 (max for unit startup is 255amps).

That's LRA impossible on a 2.5 ton compressor.

[wuffdog]

Yes, when I disconnect the wires to the compressor, the breaker will not trip. This would indicate a problem with the compressor, yet no shorts or grounds are indicated.
As for the LRA, the data plate states max LRA 255Amps.

[Mr Bill]

Originally posted by wuffdog
As for the LRA, the data plate states max LRA 255Amps.

I would like to see how they tested that, or maybe some engineer just figured that without testing, What they hooked it up to a 300 amp panel box, If that compressor ever see's a day were it draws 255 amps trying to start you won't have to worry about it anymore the terminals will probably be laying in your neighbors drive. :D

[HVAC Pro]

My vote is bad breaker.

[splitbolt]

Originally posted by HVAC Pro
My vote is bad breaker.

Curious, would there be any indication of intermittent arcing on the contactor points if there was a bad leg on the breaker?

[HVAC Pro]

Originally posted by splitbolt

Originally posted by HVAC Pro
My vote is bad breaker.

Curious, would there be any indication of intermittent arcing on the contactor points if there was a bad leg on the breaker?


Possibly, but I doubt it. Sounds like a weak trip mechanism in the breaker that can't overcome normal starting torque.

[wuffdog]

Thats the only thing left to try as far as I know, replacing the breaker. I'll give it a shot tomarrow and see what happens. thanks for your input one and all.....

[t527ed]

agree with bad or loose breaker

[Black Adder]

I don't know about the last thing I would try, I think trying a new breaker would be one of the first things I would try. Have seen plenty of faulty breakers in my time.

[reverunbilly]

Originally posted by wuffdog
Yes, when I disconnect the wires to the compressor, the breaker will not trip. This would indicate a problem with the compressor, yet no shorts or grounds are indicated.
As for the LRA, the data plate states max LRA 255Amps.

did you check the compressor with a mega ohm meter? if the windings are going bad the meter will show it.

[bornriding]

totally agree with Reverunbilly, sounds like windings are getting hot, then grounding or shorting out - use megger to ascertain condition of windings, and supply wiring