Heat Pump problems - http://www.hvacmechanic.com/ Forums
Original message
| ETaylor
 |  "Heat Pump problems"
, posted Sat 1 Nov 22:01:  
I have spent the day troubleshooting my 1.5 year old American Standard heat pump. It is a 2 ton 13 seer package unit. The problem is, during heat call the suction pressure drops out the bottom and the LPS opens.The unit energizes reversing valve during cool call. I thought maybe I had a low refrigerant condition, so I checked pressures during cooling call. (It was warm today) I found that unit was a little low. I charged according to subcooling chart. It only took 12oz to bring it back up to speed. But, the unit still had the same problem during heat call. The indoor coil is being fed wih hot gas until LPS opens. I am not sure whether reversing valve is sticking a little and not allowing flow back to compressor, or TXV off outdoor coil has restriction. It seems if TXV had restriction it would be evident in cooling mode also. My brain is fried, any ideas.I am also looking for any IOM literature for this unit, I cannot seem find anything online. Thanks.
[this message was edited by ETaylor on Sat 1 Nov 22:20] |
| Replies:
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| t-stat
| "Re(1):Heat Pump problems" , posted Mon 3 Nov 06:18
1@is the reversing valve energized in the heat or cooling mode?
2@what are your ambient conditions indoor and outdoor?
3@what are your pressures and temperatures at the compressor
suction and discharge lines?
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| | ETaylor
| "Re(2):Heat Pump problems" , posted Mon 3 Nov 07:45
The valve is energized in cooling mode. The outdoor temp was 79 and the indoor temp was 69. In cooling mode the pressures were 155 head and 67 suction. liquid line temp was 73.5. In heat mode the head pressure was 155 and the suction started at close to 70 and then fell rapidly to 20 or 25 where LPS cutout.
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| | t-stat
| "Re(3):Heat Pump problems" , posted Mon 3 Nov 16:02
that head seems low to me, the suction looks fine.
i'm leaning on the reversing Valve.
did you do a temp difference on the reversing valve?
to be honest if that reversing valve seems like it's leaking by ,
better replace it before it takes out your compressor.
do you have the skills/tools to do this?
now the Expansion valve, I'd put on the back burner for now, because it would not act the same in both heat/cool.
you should have 2 TXV's fitted each with a bypass check,
so if one valve is faulty, it would be bypassing this valve to feed the other coil in the reverse mode.
if your not sure on how to check your reversing valve,
just go into your wholesaler and photocopy the info out of a Reversing Valve Box.
you got me curious now ,good luck.
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| | ETaylor
| "Re(4):Heat Pump problems" , posted Tue 4 Nov 19:50
okay, the installer never showed up. I checked the reversing valve. I even ran the unit in cooling with outdoor fan disconnected and in heat mode with indoor fan disconnected to get head pressure up to see if this would unstick valve. I am getting hot discharge off compressor through to indoor coil. I am also getting cold suction back through valve to compressor suction line. The suction pressure starts out okay 73, but after about 30 seconds begins to fall out the bottom. I bypassed the LPS and if I let it continue to run, the suction side goes into a vaccum. Energize the reversing valve and the refrigerant balances back out.Ran out of daylight. The TXV is located under top where outdoor fan is mounted inside condenser coil. This is going to be very difficult to troubleshoot with unit running.
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| | ETaylor
| "Re(4):Heat Pump problems" , posted Tue 4 Nov 07:03
I am an HVAC tech, but I usually work on commercial. This will be my first heat pump. But, I believe with a little bit of tech info I can handle it. I got home after dark yesterday and it's still warm here so I'll try to check it tonight, if the guy I had install it does not come again today. He said he would look at it for me because he just installed it a year and a half ago. Let me get it straight. I looked, there are two TXV's, so your saying if there was a restriction in the exp valve on outdoor side the bypass check would bypass this valve and use the indoor coil valve?
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| | t-stat
| "Re(5):Heat Pump problems" , posted Tue 4 Nov 19:42
"Let me get it straight. I looked, there are two TXV's, so your saying if there was a restriction in the exp valve on outdoor side the bypass check would bypass this valve and use the indoor coil valve?"
1 txv for cooling and 1 for heating, but if you put the unit on heating and your suction falls off to cutout.then you put the unit on cooling and your suction falls off to cutout, sounds like a lack of refrigerant.
recover the charge and try to pull a 500 micron or lower vacum
this will insure there is no leaks, dial the charge back in the unit and see if this corrects your problem.
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| | ETaylor
| "Re(6):Heat Pump problems" , posted Tue 4 Nov 19:53
In cooling mode the suction pressure does not fall it was running at about 70 on Sat when I checked it.
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| | t-stat
| "Re(7):Heat Pump problems" , posted Mon 10 Nov 04:23
So,did you check your charge of refrigerant?
just remember, you have a much better heat load in the cooling mode,
so don't let the heat/cool pressures fool you.
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