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technut1054 · Jun 16, 2009, 09:17 PM

I have a 1 ton Trane heat pump used for heating/cooling of my basement, it has been seldom used over the years. When I put the Stat in Cool mode the unit seems to work: the outside unit kicks on, with the contactor closing in and compressor pulling 6.5 amps continuously with condenser fan running however no cold air is produced from the inside air handler, only room temperature air is blown. I'm thinking the reversing valve my be defective since last fall when I last tried to use the unit in cool mode it would cycle hot then cold, hot then cold and so on. These hot summer days are making me need to figure out what's wrong with it.

Another thing I notice while checking the compressor amps was the air coming off the fan was much cooler than the outside ambient air, whereas the air coming fan the 1.5 ton unit next to it that was working properly was warmer than the ambient air. Is the reversing valve stuck in the heat position? Any suggestions?

hvac1000 · Jun 16, 2009, 10:03 PM

Is the reversing valve stuck in the heat position

That is a good possibility or the coil on the rev valve could be defective also. Try going from heat to cool a few times to see if it will move the valve.

dac122 · Jun 17, 2009, 06:14 AM

With such minimal lift between your indoor and outdoor temp, if you reversing valve was stuck in heat mode I would think you'd be producing around 12,000 BTUs of heat for your basement. So is it heating your basement or is the more like the supply air is neither being heated nor cooled?

technut1054 · Jun 17, 2009, 08:59 PM

Originally Posted by dac122

With such minimal lift between your indoor and outdoor temp, if you reversing valve was stuck in heat mode I would think you'd be producing around 12,000 BTUs of heat for your basement. So is it heating your basement or is the more like the supply air is neither being heated nor cooled?

I tried going from heat to cool several times as HVAC1000 requested. The Stat temp went from 81 to 83 degrees in about 15 minutes. I apparently can get heat but not cool. When in Cool mode the supply air is neither being heated nor cooled as you stated, it just maintains the room temp even when I set the Stat to Hold at 77 degrees.

FYI, I have three HP's side by side. A 1.5 ton for the upstairs, a 2 ton for the main level and this 1 ton for the basement. When they all are running in Cool mode the air being blown from the outside compressor/condenser fan is warmer than ambient air for the two units that are working properly whereas the outside air being blown from the compressor/condenser fan on the basement unit that is not working properly is noticeably cooler than the ambient air.. Isn't that a sign that the HP is running in heat mode even though it is set for Cool?

KC13 · Jun 17, 2009, 09:28 PM

Connect the "R" and "O" circuits together at the outdoor unit. If it cools, the problem is in the thermostat or control wiring. If it still heats, check the reversing valve coil and wires. If they are OK, the valve slide may not be traversing fully to the cooling position.

technut1054 · Jun 18, 2009, 08:03 PM

Originally Posted by hvac1000

Is the reversing valve stuck in the heat position

That is a good possibility or the coil on the rev valve could be defective also. try going from heat to cool a few times to see if it will move the valve.

Toggling between Heat to Cool a few times didn't do anything.

I measured 24 V ac across the reversing valve coil and also measured the reversing valve coil ohms at 10.5 ohms. Any other ideas?

T-Top · Jun 18, 2009, 08:16 PM

If your heat pump is stuck in heating mode the leaving air temp will be a lot higher than 3 degree rise. Your low on freon or the compressor is not running at all. If the out side fan is running on the heatpump it does not mean the compressure is.

hvac1000 · Jun 19, 2009, 01:26 AM

You may have a sticking slide valve in the reversing valve and usually that means the reversing valve will need to be replaced. I have had some luck in the past using Supco 88 oil in the system but you really need to know what you are doing to take part in that game.

technut1054 · Jun 19, 2009, 08:00 AM

Originally Posted by T-Top

If your heat pump is stuck in heating mode the leaving air temp will be a lot higher than 3 degree rise. Your low on freon or the compressor is not running at all. If the out side fan is running on the heatpump it does not mean the compressure is.

I believe the compressor is running since I measured it drawing 6.5 Amps with a clamp-on amp meter.

KC13 · Jun 20, 2009, 10:14 AM

Try this: with the system operating in cooling, disconnect the "O" circuit wires from each other at the outdoor unit. You should hear a "gushing" sound from the unit as it switches over to heating. Wait a minute, then touch the wires together - you should hear the same "gushing" again as it switches back to cooling. If not, repeat this process every 10 to 15 seconds for a couple of minutes to see if the valve starts working again. The outdoor discharge air temperature will give you some indication as to what the system is currently doing. There may be something (solder, etc.) lodged inside the valve and this process just might allow it to pass.