I bought a house last year, and the AC unit, a Trane XE 1000 Mod no. TTR025C100A2 has not done a very good job of cooling my house. It runs all day and night and doesn't cool the house more than a few degrees on the best of days.

I had a technician come out and look at it and when he pulled the shroud off the outside unit we saw that the coil was caked with years worth of gunk. We cleaned the gunk off and the AC still was not cooling. So we checked the lines going into the indoor coil and the coolant supply line was hot and the return line was cold and sweating. It appears that coolant is moving backwards through the system.

The technician told me that he suspects the filter-dryer broke, which caused the pellets it contains to be flushed into the lines, causing a blockage. He said that the entire system, indoor and outdoor, needs to be replaced and all lines flushed to remove all the blockages from the system. This is obviously a very expensive proposition.

I also have a Honeywell RTH230B electronic thermostat. In the documentation, it clearly states that it is not compatible with heat pumps. It does not have a terminal for the orange (reversing valve) signal wire. I don't know if the Trane unit I have has a heat pump or not; I'm not an HVAC person. If the system had a heat pump and the reversing valve signal was not present, it might explain why the coolant is running backwards.

So my questions are:

- Is the technician correct in his diagnosis?
- Does this model Trane use a heat pump which needs a thermostat that supports it?
- Are there any other factors that could cause the coolant to flow backwards in the lines?

Any help someone could offer in this forum would be greatly appreciated.

Cheers,
-J.

Are you saying the small line is cold and sweeting and the big line is hot?

That's exactly what's happening, yes.

OK have you looked outside for a reversing valve?http://www.drillspot.com/pimages/241/24179_300.jpg
From what I can find on the net this is a heatpump

At a glance, while the tech had the unit open I don't recall seeing something like that. But then, I wasn't looking for it at the time so I could very well be mistaken. In any event, I'll have to open it up tomorrow during the daylight hours to check.

I should also mention that I have a gas furnace. I don't know whether heat pumps are paired with gas furnaces.

How many wires at the t-stat?

There is a bundle of wires in the wall, however only 4 were connected to the thermostat. R, W, Y, G.

If only 4 wires you must just have a ac, inless they are using a heat pump for a ac only with I have seen

So if it's not a heat pump, what would cause the reversal? Same question, if it is a heat pump being used as AC?

How old is the unit outside?

Installed 1994, I think.

Well if it is a heat pump or a heat pump installed as a ac unit then if there was a problem with the reversing valve or the wiring to it would cause it not to switch. As far as the filter dryer. If that was the case then the little line should be really hot and the big line shold not be doning anything.. Because the restriction would most likely be in at your coil. There would be a really high pressure on the small line and hardly none on the big line

So at this point you suspect the reversing valve, if there is one? I'll definitely have to open this thing up tomorrow.

How does this valve operate if there is no reversing valve signal wire connected to the thermostat?

Well I am not going guess. I can not find your model showing anything to let use know if it is a heat pump or not. But there is no way that a blocked line is going to cause the unit to run backwards. Did you happen to see his gages when he was doing the service call?

I saw that he had them hooked up, but couldn't read the needles from where I was.

Has your breaker ever triped while running the unit? Intill you make sure it is not a heat pump. Not sure what else we can do. Have you ever saw ice or frost on either of the lines?

No, the breaker has never tripped. And never ice, just sweating on the small line.

It may be the compressor itself not pumping. At this pint I would say check the outdoor unit. And if it is not a heat pump then call anouther service tech for a second openion before you spend lots of money replace the entire system.

Thanks, I'll check it out in the morning and see what's in there.

If the compressor isn't pumping, how would the small line be as cold as it is and sweating?

It should not sweat inless it is actually starting to freze up