Hello, my first post. I was recommended to come onto this forum because of all the specialised advice available here.

I bought a Chinese 9kW GSHP (407) six years ago in UK and brought it over to France where I was about to build a house. House took a long time to build but eventually on 30 December I was able to switch on the Heatpump.

My system takes it's 'groundwater' from a well and the water temperature in this well was 12.5deg. C. when I started on Dec. 30.

The output hot water feeds seven underfloor loops. I have no mixer valves or thermostats. Being retired I have time to experiment and adjust.

The problem I think I might have concerns icing leading to a cool-down of the UFH water temperature, at which point I switch off.

I am a retired engineer with no particular experience in air-conditioning or heatpumps. And in France it is near impossible to get things quickly or cheaply.

The photos show the situation inside the heatpump cabinet after 3 hours' running. The pipes and smaller black canister ice up (although the smaller black canister seems to warm up sometimes and partly defrost). But the larger canister has also iced up and this is when I have noticed the the UFH water has cooled down.

My well water temperatures started on 30Dec at 12.5deg. with the return temperature at 6.2deg. C.

I have run for a total of about 9 hours in three or four sessions and the well temperatures are now at 9deg.C and 4deg. C (i.e. heatpump inlet at nine, output at four. The outlet water returns to the well; I have no choice at present. UFH water supply reaches about 38deg. C but, as I said, reduces back at some stage (I only go down to the basement to check every half-hour or so).

Ambient temperature in the basement is about 9deg. C

Might the system be going through a 'defrost' period and I should just leave it to run on? I am concerned at seeing the frosting up on the large canister.

I hope that my use of Centigrade is OK.