How we control our ASHP

by Mars

When we switched over from an oil boiler to an air source heat pump (ASHP), we had to re-think all our central heating controls from thermostats to TRVs. In this video, we break down how we now control our central heating system and how we call for heat.

We mentioned following items in our video:


JulianC 12 March 2021 - 17:43

Dear MHF.
So I’ve watched your ASHP heat control video (vid 7). I think I understand what you’ve done. But still not why you have done it.
Remembering I’m still on oil, so haven’t moved to ASHP, but why couldn’t you set your cold rooms on 5 with your TRVs (open). And then lower numbers for the warmer rooms. And then control from the single hall thermostat (say a Nest).
This means heat is called from the ASHP when the hall thermostat is below temperature. It will run quietly heating away. It just seems your solution is complicated.
This is the way our oil boiler currently works. We set the TRVs lower in the dining room. And fully open in the sitting room. I adjust the dining room up. If we are eating in the dining room. I rarely touch the other TRVs. Turn down the guest room if no one is staying.
But your vid has prompted me to ask my ASHP supplier. Thanks

Mars 13 March 2021 - 21:48

Thanks for the comments and questions Julian. Your points and observations are relevant. To be honest, the smart TRVs probably don’t need to be in play and the 1-5 TRVs would work. What is nice about the smart TRVs is that we can set ‘exact’ temperatures in rooms.

For us, in our house, a central thermostat wouldn’t work because our house runs north-south. The central to northern portion of the house get and stay warm; the southern portion struggles. So we have the smart thermostats in the southern rooms, and they are almost always calling for heat from November to March/April. Since they are, the radiator circuit is always open. In March/April, the smart TRVs regulate the room temperatures in the norther portion of the house quite well. But that has little bearing on energy use and savings.

The UFH with the smart thermostats from Heatmiser work perfectly.

We have a complicated set up, but this is the only way we could get our heating to be customisable for our house. We just found that we needed to add these various elements after we stopped using oil to prevent the ASHP from coming on unnecessarily, which was never the case with oil.

I suspect in your case, you’ll just leave your TRVs set to 5 because you’ll want maximum coming through. The one thing you’ll notice about ASHPs, is that there’s no point in turning the guest bed down, because your ASHP is heating the buffer, so whether that guest bed is on 1 or 5, you’ll be using the same amount of energy to heat the house. Nevertheless, I still think it’s a good idea to have a conversation about this with the installer (as you are) just to get clarity and peace of mind.


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