Michael_S

Thanks for the comments so far. OK - there is power going to the pump. So we took the pump apart and it seemed to spin fairly easily by hand. It did not seem to turn when connected to the heat pump, so then we tried connecting directly to a power supply and it did not turn either - except one time when it did, but we can't make it do so again. So now we are not sure if the pump is working or not and they are hardly a cheap swap out part. Can they be replaced by any random pump of the same power or does it need to be one with electronic control via pwm? Thoughts?

Sorry for hijacking a thread. We have a new to us 12kw Thema V (perhaps 6 years old) but on connection we are getting the dreaded CH14. I am wondering if the circulation pump (a wilo) is working at all. Any suggestions for confirming it is actually running, I can't hear anything or feel any vibration, turning the speed/pressure selector makes no difference. It has been siting for awhile so might be seized/rusted. I can not see the the end of the spindle to insert a screwdriver as the control unit is on the end not the side so I am not sure if this model has screwdriver access or whether it needs to be unbolted in half to manually try and loosen the impeller/spindle. Thoughts?