Fabric and ventilation heat loss calculator

[JohnMo]

I would size heat pump based on a few criteria 

 

Over size ashp approx 1.2 to 1.4 for region of +5 to 0 to allow for defrosting. 

 

Make sure heat pump puts out a genuine minimum of 7kW at you design temp. Take note also of oversize to cover defrosting.

 

Get a heat pump with good modulation.

 

Size system volume based on

20L per kW output at minimum modulation of heat pump. Exclude in volume calculation any radiators with trvs and their pipe work. Exclude any UFH loops with actuators. Any volume needed, add by volumiser not buffer.

[Sparrowhawk]

3 hours ago, timhowes said:

However, as someone with no prior experience, I will have to be quite brave to source my own ASHP, design the system and ask them to fit it.

 

Consider going to a HeatGeek accredited installer, because they know their stuff and will install outside MCS or may be able to get a reasonable system design through MCS. And a HeatGeek installer will appreciate that you've already done a basic heat loss calculation to size up the previous system design!

[timhowes]

Thanks @Sparrowhawk - I contacted a HeatGeek recommended installer back in July who sent me a quote for a mere £25k!!! This included 7kW ASHP (a premium Stiebel Eltron model), all of the UFH I will need, and before the BUS grant. But still...

 

So this sort of put me off. I have gone back to them to ask to discuss, as they are the only company who have entertained the idea of an appropriately-sized ASHP. I have said no buffer, single zone... Let's see what comes back!