Can’t get Daikin Althema to be controlled by LWT

[MechanicalBuilder]

I’ve been trying the ‘open loop’ method of running my heat pump but the daikin Altherma HP will not stop cycling! I have set the control to LWT rather than external stats but something is calling for heat and running the compressor. Even with a LWT as low as 28-30’c I managed to consume 10kwh over night. The house is a brand new build and doesn’t really need much to keep it at 21’c

[JohnMo]

Things I figured out

 

Monitor what happens just prior to a compressor cycle occuring. And when it stops. I then set my target flow temperature around this. So set a WC curve around this also.

 

For my system if I don't have the circulation pump on all the time there is plenty of cycling.

 

This is my ASHP at the moment. It's about 4 degs outside.

 

The WC curve is set to coincide with a return temp at 22.7. At the moment I have a run time of just over a hour and an off time of 40 mins. 

 

Read and then read the manual many more times to understand what you can and can't do with settings. dT starts stop hysterisis all make a difference to run times and cycle times

 

[DamonHD]

On 26/10/2024 at 21:09, MechanicalBuilder said:

I’ve been trying the ‘open loop’ method of running my heat pump but the daikin Altherma HP will not stop cycling! I have set the control to LWT rather than external stats but something is calling for heat and running the compressor. Even with a LWT as low as 28-30’c I managed to consume 10kwh over night. The house is a brand new build and doesn’t really need much to keep it at 21’c

Note that the antifrost feature will run the circulation pump and possibly the compressor if outside temperatures are at/below 7C.

 

I'm also seeing my Altherma eat a lot more energy that I exepct when running it open loop with a weather-comp LWT target, cf running it when needed with an external call for heat.