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Regan Land
Regan Land, HVAC Technician
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3 ton Rheem heat pump, R22, manuf. date 1997 Customer complaint

Customer Question

3 ton Rheem heat pump, R22, manuf. date 1997
Customer complaint: Only getting heat from heat-strips as condenser unit will not run in heat-mode.

When we (my assistant brother, Ernie) and I arrived this past Sunday, 2/14/10, I found the condenser disconnect lying on the ground; my niece had had another AC company out, tried to diagnose the problem, said they’d get back to them, but never called Becky back. I turned thermostat to heat & set it up to 85oF. The AHU came on fine, but when I inserted the disconnect at the condenser unit…. nothing happened. I hooked up my pressure gauges and pushed the reset button on the condenser unit….it started up and I watched the psig on high-side spike to over 375 then the condenser unit shut-down completely… I assume on high-pressure control.

Suspecting that heat was not being rejected at the AHU, I cleaned the coils to the AHU (I was surprised to see that they were pretty clean; although, I did find a caked filter indoors in the ceiling and removed it). I then pushed the reset button to the condenser, it started up, rose to 375 then cutoff on high pressure, again.

I cleaned the coils to the condenser unit (it was dirty); pushed reset button, started up, rose to 375 then cutoff on high pressure a 3rd time.

Called Bob Nolan at SSC. He said it was either overcharged or there was a restriction in the refrigerant line.

I checked the refrigerant lines, there were no crimps or obvious restrictions (although, I did not find a filter-drier at either condenser or AHU areas… that was odd!). I then switched the system’s thermostat to “cool” mode. The whole system came on and I ran it for 2 minutes in cool-mode… pressures appeared normal (260/70).

I then switched the thermostat back to ‘heat’ mode and the high-side pressure spiked and cut-off; I could hear the jet-sound of the RV, but could not determine if it was fully engaged in the heat-mode. I then recovered maybe a ½ pound of refrigerant (thus keeping high-side pressure down to around 260). While the condenser was running, I worked to remove refrigerant and kept the psig under control, the compressor started sounding strange (heard what seemed to be an internal hissing noise from the compressor), it then got real hot, and I assume cut out on IOL; I ohmed the compressor out, it was OL … C to R and C to S. We ran out of time and I had to go, so I assume the compressor cooled down and reset itself. I left XXXXX XXXXXke I found her – only getting heat from the heat-strips.

What just happened? Is it fair to say that the problem lies w/ the RV or the TXV at the condenser? How do you know if the RV is no fully engaged?
Submitted: 6 years ago.
Category: HVAC
Expert:  freon replied 6 years ago.

Hello,

i will try to help you on this one. The unit does sound like it is over charged! this is usually what happens when someone tries to charge the unit in cooling mode during cool weather. My suggestion is to either wait for warmer weather (65 or higher) and check the system charge in cooling or keep removing refrigerant (according to EPA guidelines of course) a little at a time until the compressor bypass no longer engages.

 

 

I dont think you have a restricted drier or faulty rv at this time.

 

 

 

Customer: replied 6 years ago.

I went back to the home last Friday; temps were near 70 deg F. I turned the system on to "cool mode" and the pressures were 160/45... the evaporator at the AHU was freezing up. So I don't think it's overcharge. I am currently poised to replace the outdoor TXV as I suspect it is restricting refrigerant. In "heat" mode the head pressure spikes almost getting up to 400 psig before the system is cut out on 'high pressure'.

 

 

So, do you think my premise is plausible?

Expert:  freon replied 6 years ago.

Well not sure. Did you happen to see frost near the TXV or RV showing a restriction?

You also have a check valve in the evaporator coil that might be stuck... if you can get to this you should try tapping on it. Some of the newer check valves are in the evap TXV.

 

Expert:  Regan Land replied 6 years ago.
Hey freon, check your PM's
Expert:  freon replied 6 years ago.

what is the pressure at the "all time" suction port in heat mode. If the head pressure is spiking at 400 psi, but the all time suction is going to 0 psi, then the outdoor TXV needs to be replaced. Try this and let us know!

 

Thank you.

Customer: replied 6 years ago.
Let me state what I think I'm hearing from you.... Yes, the pressure at the "all time" port eventually goes down to Zero. So, you think the problem lies w/ the TXV at the outside unit rather than the check-valve at the inside unit?
Expert:  freon replied 6 years ago.
No, what i am saying is that it could be either place. Check both places. Normally you would see frost or a temperature difference at a restriction. So you should check at these areas for sure.
Expert:  Regan Land replied 6 years ago.

If the all time low is going down to 0 psig and the head pressure (at the liquid line port) is going to 400 psig, then it is a bad outdoor TXV.

 

If it were the indoor check valve (or anything else between the compressor hot gas line and liquid line port), then the pressure at the liquid line port would be at 0 psig also.

Regan Land, HVAC Technician
Category: HVAC
Satisfied Customers: 566
Experience: 18 years of experience, NATE Certified, Licensed HVAC Contractor, Certified IAQ Specialist
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