Compressor Stalling

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  #1  
Old 06-15-08, 07:53 PM
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Question Compressor Stalling

The Compressor in the outdoor unit of a split system stalls after it has been running for several seconds. I just had this unit relocated to a different location & think the tech overcharged it. As when the contactor closes the compressor runs as described above then starts to shake as it is slowing to a stall. A few seconds later the contactor drops out. The whole time the fan on this unit keeps running.

I have checked resistance in both windings on the compressor, both start & run capacitors & the soft start relay unit- all check out OK.

Any suggestions would be appreciated.
 
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Old 06-16-08, 02:56 AM
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I'd have to agree with you. Have the unit checked for a possible overcharge.
 
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Old 06-16-08, 03:56 PM
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Did you relocate it to an area with enough fresh air ? The unit might not be getting enough air to cool the compressor and is overheating. That's what i'm thinking. Your going off on high head pressure. That would also explain why the fan motor keeps running.
 
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Old 06-16-08, 04:31 PM
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Woops sounds like the poor fella forgot to open the king valves lol now that is embarrassing.
 
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Old 06-16-08, 04:46 PM
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Yes, lots of ventilation. But as the compressor only ever runs once for several seconds on each power-up of the local main isolator I don't think this is the main cause.
 
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Old 06-16-08, 04:51 PM
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Forgot to mention, I know form an eye witness he had his guages connected while charging, but I don't know if he got the compressor running during his visit. Just got the report that it was faulty & he would need to return with parts. I have him on hold till I get some info from you kind helpers.
 
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Old 06-16-08, 04:52 PM
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Big D my guess was that the guy pumped down the unit into the condensor and locked out the refrigerant cutoff valves. He then relocated the unit and hooked the lines up and pulled a vaccum and charged the lines back up. But failed to open the valves releasing the stored refrigerant back into the sytem and now the compressor is pumping against a dead head and kicking out on high pressure. Hard to believe that he would not test run the unit before he left but for all we know it may have been real late when he finished up? Post a pic of your unit where the lines connect there are probably two large brass valves with the service fittings on them?
 
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Old 06-16-08, 04:54 PM
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I think Saturn is right then, the King Valves must be closed. I'm not even going to try and walk you through this but you gotta open them king valves and if you don't have gauges or know your suction side from your high side then your going to make things worse. Shut it off before you fry it and wait till he gets back.
 
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Old 06-16-08, 05:02 PM
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Many thanks for your kind replies.
I did check the shut-off valves for both Gas & Liquid on the side of the outdoor unit. They were both open to my limited knowledge. (Took off brass caps and opened valve with a hex key, got a few more turns out of each, but they were a few turns open already)
 
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Old 06-16-08, 05:18 PM
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Well it sounds like the unit is going off on high or low head pressure. Something is not right there.
 
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Old 06-16-08, 05:24 PM
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Are the HI & LO cut-off pressure switches contained inside the compressor itself ? As the contactor is still in when the compressor stalls. The contactor then opens a few seconds after this.
 
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Old 06-16-08, 05:26 PM
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Hmmm sounds like they are open if they are completely backseated. Dang I thought I had it. Ok next guess is that (If this is a heat pump) then I think he failed to hook up the tstat wiring correctly and the condensor is in heat mode and of course kicks out on high pressure real guick. Most units (not all) will default to heat mode (if reversing valve is not energized) so I am thinking he failed to hook up the t-stat reversing valve wire. He had to relocate the t-stat wires so we know he had them unhooked at the unit right? Not sure when your man is coming back but we may find his mistake before he makes it maybe.
 
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Old 06-16-08, 05:36 PM
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Thanks for the input Saturn (& others) but the t-stat is inbuilt into the indoor unit. All temperature & mode functions (heating, cooling etc.) are controlled by a hand held remote. Like TV !!

Looks like the over charge is the only conclusion still floating !!

Might get him back. How is he supposed to know what charge to supply. Does he go off weight from a book or pressure on his guages?
 
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Old 06-16-08, 05:43 PM
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Is this a split system heat pump? If so it has a reversing valve and the valve is not energized almost sure this time LOL. this is more fun than watching TV so lets not stop yet
 
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Old 06-16-08, 05:58 PM
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I think what you mean by "Heat Pump" is does the unit Cool & Heat. If so yes it does. I do hear the loud click associated with a solenoid activating just before the contactor pulls in. This happens in one mode heating or cooling ( can't remember which) but not the other.
 
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