On 13/11/2020 13:42, Theo wrote:
As far as a retrofit goes, that cooler water means you may need a radiator
upgrade if you don't have UFH.

nearby neighbour living in a 1976 4 bed detached house had
this installed. (Air to Water).

They had to replace all 8 rads with triple-panel finned rads at
£300 per rad (that was over 12+ years ago).

They stopped using their Potterton Supreme gas boiler at the
same time but then found it was impossible to get anyone to
'service' their central heating system because no-one knew
what they were supposed to do.

I asked her what it was like in winter, and her reply was
"i'm freezing all the time". Luckily this house had had an
external class 1 chimney added by the 1st owner so her other
half could spend lots of his time in winter collecting wood
scraps to burn.

The compressor is the size of a US-style double fridge but
it is on a North facing wall so permanently in shade. I suspect
this makes a big difference because here in Sussex the solar gain
in winter is very noticible. On a really cold day, even with
bright sun, the air at the back of the house is still cold.