[Tonelious]

I have a Cold-flow water to air heat pump its less than two years old. Recently its developed aproblem when the unit kicks on in heat mode it runs about 5 minutes then the compressor and water pump shut off though the fan keeps running. The unit works fine in ac mode. I put in a new programmable thermostat this spring but it worked fine all summer. I had a tech come look at it he said it was water-pump but I had it checked it works fine. I should add neither the compressor or water pump is hot when they cut off. And they will restart if I shut the unit off and cut it back on.

[hvac1000]

I highly suggest you contact a company that is very familiar with water to air heat pumps. There is a lot more going on with these style units than with a regular heat pump. It looks like you need to find a new tech.

[Tonelious]

That's easier said than done I had two different companies come look at my old one. And I ended up fixing the thing myself. Now this makes the third company that's been out and none of them seem to know anymore about the system than I do. I was hoping to find someone on this site that could steer me in the right direction. Before I get another ac tech that gives me bad information

[hvac1000]

You need to find out what control is dropping the unit out after 5 minutes. Process of elimination works,using a meter will work,OR jumping each control out one at a time till it stays running UNLESS it is a safety control. I started using copper coils in lakes and ponds back in 1978 to provide water to water to air or water to water heat pumps so I guess I have some experience but I do not have the time to have a long extended conversation or on line diagonsis since there is more involved with these types of systems than others.

Find the control causing the problem and post back with the results.

Answer these questions also.

Did the unit run in heat mode after you changed the thermostat? In other words the unit has been producing heat all this winter up till now?

Is power being applied to the reversing selonoid or not? You stated the unit runs 5 minutes but the compressor or pump is not hot?

Since the system worked in the A/C mode it should work in heat but the reversing valve could be activated causing it not to heat. That is if the system is designed to default run in the heat position. Like said this is just the tip of the iceburg.

[Tonelious]

Thanks for your help hvac1000 Its really appreciated. I`m doing this before and after work so its slow going. So here`s what I know so far

The unit has not run this winter with the new thermostat. I changed it out the old one had a burnt contact at the cool/off/heat switch it was an old honeywell the round type. I was careful to wire the new one exactly as the old. It's a rite-temp from homedepot.

The o wire at the thermostat is energized in heat mode I have not traced it further but from the wiring diagram on the heat pump the fan motor relay is also powered by the same wire.

I was mistaken the compressor is not starting when the unit is turned to heat what I was hearing was the waterpump cutting on it then runs for 3 to 5 minutes then cuts off. Which it should do if the compressor is not running. Testing at the thermostat the why wire is not energized when the unit has switched to heat. On Monday I turned the ac on. The temp outside was near 70. And everything appeared to work fine and as I said earlier it worked fine all summer and last winter.

In my first post I left out that when the tech came out the unit was completely dead it just made a humming sound. But the waterpump came on and ran its five minutes then cut off. He changed the fan run capacitor and the fan began running that's when he told me that the waterpump was cutting off causing the compressor to cut off as a safety feature.

I have a ac guy coming out next week that was recommended by a friend but when I asked he said he doesn`t know a lot about the water to air most of the homes in our area had them but as they get older most people swap them out for air to air.

I guess my question now is should I just get a new thermostat what kind should I get this one said it worked with heat pumps?
Should I just wait till next week?
The wiring diagram on the unit shows the wire running to the reversing valve as the o wire am I correct in assuming this means it should be powered in cool mode not heat as it would be the be wire if it was powered in heat?
I am going to try testing the controls one by one as you suggested tonight but if the thermostat is not operating correctly. Is that going to do any good?

[hvac1000]

You can test the controls without the thermostat. Usually heat pump reversing valves are designed to fail in the heat mode and you have to activate the selonoid valve in the cooling mode to get A/C.