Author Topic: heat pump not warm enough or holding set point  (Read 2055 times)

Offline junichi

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heat pump not warm enough or holding set point
« on: November 13, 2014, 11:37:29 PM »
Hello, my whirlpool heat pump is not producing enough heat to hold my 72 degree set point in temperature from 30-37 degrees. It is an add-on to an oil furnace controlled by a Honeywell TH 6320R1004 and the EIM is a Honeywell THM5320R.


All batteries new and filter replaced
Does not go into defrost mode (timed)
Aux heat sometimes does not turn on
Temp dropping well below set point
Manually put in cooling mode and it worked
T-stat sometimes flashes "heat on" when heat not on
Air temp lower than usual
Em heat will turn on manually and maintain set point

I took the batteries out of the t-stat and outdoor temp sensor and while they were out, the furnace fan came on with no heat!

Furnace 7 years old, heat pump etc 3 years old.

Suggestions? Thanks

Offline Admin

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Re: heat pump not warm enough or holding set point
« Reply #1 on: November 14, 2014, 04:05:11 PM »
My guess would be a bad control board in the heat pump.

Some Honeywell thermostats will have a 5 minute delay and flash HEAT ON until the delay is over.

Perhaps disconnecting the OD sensor fooled the thermostat into thinking there was a fault.  Sometimes the fan runs when there is an error.

Does the outdoor coil actually ice up?  Maybe we have refrigerant problem, but it does seem more like an electrical problem.

A bad control / defrost board in the heat pump could be the reason the defrost mode and AUX heat are not being energized.

It sounds like the thermostat and oil furnace are functioning correctly.

The heat pump parts might have a 5 year warranty.

Good luck!

Offline junichi

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Re: heat pump not warm enough or holding set point
« Reply #2 on: November 14, 2014, 08:45:14 PM »
Thank you for the insight.  There is a control unit in the heat pump.p outdoor unit? Or is this the Honeywell control board attached to my furnace that communicates with the thermostat?  My suspicions are also that it is electronic and not mechanical...

I called Honeywell today and many of these symptoms my be attributable to the 'Learning' thermostat. We experienced a sudden change in weather pattern here and it may tame the thermostat a week to adapt. I am hopeful that this is the case because it seems as though the performance of the system is gradually getting better. At first no aux heat..then it started to work. Last couple nights the set point was maintained, but not the few before. And tonight, the heat is definitely warmer than before..perhaps indicating the thermostat has finally figured out it needs to move to 2 stage heat. A few more days and it may be fine...fingers crossed that is the case and that I don't need a new control board in the heat pump!

I will post in a few days when I know.  For now, it is great to have an idea of what I might expect to replace and the cost...thanks again for the response.