I own a Climatemaster TTV64 (5 ton, 2 stage) geothermal heat pump that is controlled by a Honeywell TH8000 series thermostat. The system was installed in 2007 and it has performed almost flawlessly until last Thursday.  I have documented its great performance,  previoiusly on this forum.
 
The professional who installed my geothermal heat pump (2.5 yrs ago) left on vacation last Friday and designated the job to his on call technician. However the technician is too busy and can only come over on Monday afternoon. He has tried to help diagnose the problem over the phone with limited success. It has been very hot in south east PA and I am trying to understand if there is a problem with my thermostat.

Sometime Thursday evening, I noticed that the heat pump had shut down. The fan continued to run and the ambient temperature in the house was 80 F while the set point was at 78 F.

There are new batteries in the thermostat and a relatively new filter in the heat pump.

Thinking that the problem was probably with the thermostat, I reset the thermostat – turned it off and then waited some time and then turned it back to cool. The heat pump came on and started cooling the house.

The next morning (Friday) the heat pump was again off but the fan was running. Temperature in the house was above the set point of 78F.

I called the Installer to tell him know that the heat pump had stopped working again. The installer’s technician asked me to check for errors indicated on the CXM board. The green light was blinking fast (on off on off ) at a constant frequency but there was NO pause between a series of blinks. The technician said that that was not an error code. The heat pump was just waiting for a signal from the thermostat to start cooling. However the temperature was above the set point and the thermostat was indicating that it was asking for cooling.

I again shut down the thermostat and then turned it on. The heat pump (compressor) came on and began to cool. At this point I went to work but later my mother, who is visiting, called to say that the heat pump had shut off.

In the evening the temperature in the house was 85F while the set point was at 78F. As before, the fan was running. The LED on the CXM board was blinking on and off at constant but slower frequency. I removed the batteries from the thermostat, waited for 10 minutes, replaced the batteries and then turned the thermostat to cool. The heat pump came on and ran for about 20 minutes then shut off. Temperature in the house was 83 F and still higher than the set point. But I cannot recall if I had increased the set point. The LED on the CXM was blinking slowly at a constant frequency.

The technician still thought that there was no error code. He asked me to remove the thermostat from the base plate and jump the red ( R) wire to the Yellow ( Y) and Y to the Green (G). When I jumped Y to G the fan came on and jumping from R to Y turned on the compressor. The ECM blower ran at a very low speed. The metal inlet and outlet ports of the water loop were both very cold but the air was not cool as it came off the pump.

At the technician’s suggestion, I then jumped the black wire (Y2) to the Green (G). The blower speed went up significantly and the compressor ran for a shot time and then shut down. This time there was an error code on the board - two short blinks with clicking sounds and a long pause (on off on off pause on off on off pause) and this pattern repeated itself.

Technician now thinks that the water pressure in the loop is low. Why that would be is not clear but he intends to come in on Monday afternoon and if needed recharge the loop.

The heat pump still runs over short periods but turns off, inexplicably.  Sometimes it turns on and then shuts off within a minute.  Everytime it shuts off the LED blinks on and off at a slow constant frequency.

Could the experts on this board please suggest where the problem could be. If the problem is indeed with the heat pump there is not much I can do but wait for the technician to come on Monday afternoon. But it would still be helpful to know the cause for the problem in advance.

Thanks for any input you could provide.

Regards,

VK