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PoleCat 07-07-2010 03:28 PM

Ducane heat pump high head
I need to trouble shoot a heat pump that is dropping out I presume on high head pressure. It is intermittent. What is the highest pressure I should be seeing anyway? It shut down @ 275 or there abouts. Should I be looking at the reversing valve or the TXV? This unit is at a cat shelter and the puddies are getting warm. There is no high pressure switch in the plumbing so I figure the board can detect the situation some other way. I tried to run it with the reversing valve solenoid unplugged and the compressor shut itself off with the thermal cut out but the contactor stayed down under this condition.:huh:

beenthere 07-07-2010 04:58 PM

It isn't shutting down on high pressure if it doesn't have a high pressure switch.

Check both pressures, and the line temp of each line.

PoleCat 07-08-2010 06:41 AM

Maybe some more info will help. This is a package unit. Stopped working last week. The air handler was blowing but no compressor or outside fan. A reset at the thermostat would get it going again but it would shut back down within a few seconds to couple of minutes leaving only the inside fan running. ( contactor released ) It ran long enough for me to check pressure one time. The low side went from 130 @ idle to 68. The high side climbed rapidly from 130 to about 275 then the contactor released. I felt the pipes at the reversing valve and found cool from inside coil cool to compressor hot to outside coil. The outside coil was cleaned and air filter changed to no avail. I left stumped. The owner called me later that day to say it was working again. I was out there yesterday and it had stopped working. Same thing. I checked the low pressure switch ( out of desperation ) and it was ok. I wondered if it would work in heat and pulled the plug to the reversing valve solenoid. ( I am doing all this outside and the thermostat is still in AC. I am resetting by unplugging the 24V transformer. ) Anyway, it started and ran for about 30 seconds. This time the compressor began to lug and stopped abruptly but the outside fan continued to run as there was no contactor release. After a few seconds it restarted and did the same thing. (I am going from one side of the unit to the other checking on this.) I pulled the transformer connection again to release the contactor then went back around to feel the compressor. It was hot as blazes on top and sweating on the bottom. :eek:

beenthere 07-08-2010 07:11 AM

Is there a drier in the liquid line. Could be plugging.

PoleCat 07-08-2010 07:41 AM

No filter dryer at all.

beenthere 07-08-2010 09:20 AM

Probably a clogging the TXV, and someone in the past added some gas thinking it was low.

PoleCat 07-09-2010 03:28 PM

A tech came out today and naturally the unit ran fine while he was there. I was not there at the time so he escaped an inquisition. I'll be out there tomorrow to see if it is still working.

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