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Mr Cool Minisplit

E

EmjayAre

New member
I recently installed a MrCool mini split heat pump in our house. Chose MrCool since it was the only brand available from local retailers that provided recharged line sets so I didn't need a vacuum pump. Worked fine for a few weeks then blew the breaker. Don't know what happened since I wasn't home. Reset the breaker and worked for a while until the breaker would blow as soon as it was reset, with a flash, bang. Obviously a dead short. MrCool sent a new condensor unit which is working great. Question is: I have a condenser unit which the local HVAC companies say is probably too expensive to repair. Even a diagnosis was going to be $1000 plus. Does anyone have any suggestions about testing the unit to find the short. It is against my grain to show out a unit until I know it is truly dead.
 
the motor for the compressor is likely inside the sealed shell - that would be essentially non-repairable.
otherwise check the wires outside the shell for obvious shorts....
 
Checked all the connections and the circuit board, nothing obvious. Is there a continuity test I can do on the motor windings to rule that in or out?
 
yes - check for continuity to ground (i.e. the casing, both leads) and resistance lead to lead - if the motor has shorted internally resistance will be zero.

if you've got dancing blue coming out of the breaker, anything on the board or external wiring would be very obvious.
 
Off topic, but wanted to say thank you to all of you forum users. Lively debates and discussions, funny jokes and memes, and such a diverse group that it seems someone is always able to offer advice, no matter what is asked, just like in this thread.
I opened it, read it, and said to myself, ' how does Chowder know that '.
It's just another example of how amazing this group is!
 
I think the tech from Mrcool got me to do some of those those checks. I don't think I checked the casing. I'll do them all again.
 
Checked all the continuity and resistance measurements and no reading, not 0 so I think that is what I found with the Mrcool teck. He was befuddled and chose to replace the condenser. Any other thoughts. The circuit board, which sits over the compressor, looks brand new, which it is. It seems odd that there is no continuity between hot and neutral, this is a 110 volt system, when the breaker blew 'dancing blue' as you so aptly drscribed it.
 
hermetic motors dont like short cycles.

if the heating load load isnt enough, the unit will satisfy and not stay off long enough for the head to unload. starting under load on qo or homeline breakers sends out the dancers.

windings in the motor do come outside the sealed case. they need to be unhooked from the controller to ohm out.

just random input.
 
Just to be clear, since I'm not a genius with my multi meter, no continuity shows on the multi meter as no reading, continuity would mean a completed circuit which would read 0 ohms on the multi meter.
 
I disconnected the 3 wires from the curcuit board to the compressor. I have a black, a blue and red wire. I have attached the diagram. Blue to Black shows 0 ohms, Red to black 0 ohms, red to blue 0 ohms. If this means anything it would be very helpful, thanks

0.jpeg
 
EmjayAre said:
Just to be clear, since I'm not a genius with my multi meter, no continuity shows on the multi meter as no reading, continuity would mean a completed circuit which would read 0 ohms on the multi meter.
Click to expand...
yes, correct
 
u to v should be low.
v to w low
w to u low as well.

if they are zero or tenths, its bad
 
Thanks, I'm thinking if the inverter compressor starts with a capacitor it is possible that the capacitor failed. At first the breaker tripped when I wasn't home so don't know the circumstance. After that the breaker tripped a couple of times and since it was a new breaker I switched to one that I knew worked. It tripped after a while and then started the 'blue flash' at the breaker. I take this to mean that the motor was starting without the capacitor but putting great stress on the windings which finally failed.
 
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