Help with cruiseair AC

[helm]

Our Cruiseair AC unit has been working great but just start tripping the breaker.
It seems to pump water like a champ. The strainer is clean. I cleaned the air filter as well. It starts fine, but then the compressor seems to slow and bog down, finally tripping the breaker. Any one have any more ideas what to do before we call for service?
Thanks!

 

[Donna]

How old is the unit?

 

[helm]

Its original on our Lindell 36 - 1999

 

[sdowney717]

Do you have an amp gauge you can test the amp draw?
There is a potential relay and start capacitor, this lets it start spinning.
If that is not kicked out of the run circuit, the unit will draw too many amps and quickly shut down, usually blowing the breaker.

The potential relay and start capacitor are easy to replace. I suppose the run capacitor could also be failing.

Some of those HVAC techs will claim your compressor is shorted, when it is not. They just want to sell you a new unit.

 

[helm]

I started it and it ran at 18 amps then gradually up to 26, then a sudden surge and kicked the breaker. I guess the capacitors then?
Thanks again for helping

 

[sdowney717]

I started it and it ran at 18 amps then gradually up to 26, then a sudden surge and kicked the breaker. I guess the capacitors then?
Thanks again for helping

yes, way too much current. Capacitors, maybe, but the potential relay is likely not opening up due to an internal failure. I had to replace my relay twice over the years. Number may be on it somewhere. I have Cruisair 16k btu. The Mars relays are good.

Mars 65 19004 is the number for mine.
https://www.marsdelivers.com/item/19004/MARS-65-RELAY/

 

[TomandJeri]

I started it and it ran at 18 amps then gradually up to 26, then a sudden surge and kicked the breaker. I guess the capacitors then?
Thanks again for helping

Sounds like it's building too much pressure, until it draws enough current to trigger the potential relay and add in the start capacitor. Could be a bad capacitor, but does it have a variable expansion valve? Is the voltage at or very near the rated voltage (probably 115V)? Low line voltage for whatever reason will cause it to draw more current to output the same shaft power, which is why brownouts are so bad for motors but not most other loads. Motors also lose torque exponentially with reductions in line voltage, so it's the first thing I'd check, and it costs nothing to investigate.

 

[sdowney717]

Sounds like it's building too much pressure, until it draws enough current to trigger the potential relay and add in the start capacitor. Could be a bad capacitor, but does it have a variable expansion valve? Is the voltage at or very near the rated voltage (probably 115V)? Low line voltage for whatever reason will cause it to draw more current to output the same shaft power, which is why brownouts are so bad for motors but not most other loads. Motors also lose torque exponentially with reductions in line voltage, so it's the first thing I'd check, and it costs nothing to investigate.

That makes no sense.
The start relay and start capacitor are in the circuit at the beginning, they are not drawn in later. As the compressor begins to spin and until the motor reaches 3/4 of its rated speed the back EMF is too low to turn off the start relay. If the back emf voltage can not exceed the relay threshold it will stay in the circuit. Or if the relay coil is open circuit, the back emf voltage can not cause the relay to turn off.

 

[sdowney717]

It could be building too much pressure. It can do that if the cooling water flow is not flowing, the head pressure can go over 400 psi, but see there is an internal high pressure shut down switch, on the output high side of the compressor, they all have them, so the breaker wont necessarily blow, the compressor just turns off.

 

[TomandJeri]

That makes no sense.
The start relay and start capacitor are in the circuit at the beginning, they are not drawn in later. As the compressor begins to spin and until the motor reaches 3/4 of its rated speed the back EMF is too low to turn off the start relay. If the back emf voltage can not exceed the relay threshold it will stay in the circuit. Or if the relay coil is open circuit, the back emf voltage can not cause the relay to turn off.

I should have said 'release' the potential relay (and closing the NC contacts) rather than 'engage'. Low voltage under heavy load, or severe overload, can essentially reengage the start capacitor, which could explain the sudden large jump in current after the slow climb. Functionally not so different than a centrifugal start winding switch, though operating under different principles.

 

[helm]

Thanks for the input
The pump is putting out water like a champ
Voltage looks ok
I will try the capacitors