Is it fairly normal to have lots of different control systems as I think I have about 3 different systems trying to control the room temperature timings but only one of them actually does the controlling I think?

Heat pumps and thermal stores are bad news, really really bad news.... Who designed this system?

I don't really want to say who it is at the moment as they are currently trying to help me fix it.

@delt

I think I might have a very similar style thermal store as my installer said that the thermal store was designed to support both heating and DHW from a heat pump, so a top and bottom temperature section would make sense. Do you know if the temperatures of the sections are usually configurable?

Do you find that the house gets much colder in the evening with your setup? I have definitely found my heat pump has to work a lot harder around 5-6pm, but this is probably because I have my room smartstats bump up from 18 degrees to 21 degrees as that's when I get home from work.

I often wonder at the competence of the people who design these non-standard systems, without actually thinking about, and specifying, how such a system needs to be operated.

Having a heat store in combination with a solar thermal system is on the face of it a good idea, but does not combine very well with a heat pump and how a heat pump needs to be operated for optimum efficiency.

The designer needs to realise that the heat store cannot also act as the DHW cylinder, whilst also supplying the central heating system.

Anyway, on the positive front I have worked out some mitigation strategies that work v well for us, and may help you:

1. We only run the UFH at night (12-5am) and during the day (12-5pm), when we dont need DHW. During the night electricity is v cheap (EV tariff), so negligible cost, and this blast will warm the house for the morning. We also charge our battery overnight. 

2. During the day the external temp is typically higher, the house recieves  some solar gain, and on most days I can run the UFH off our solar PVs/battery - again the 5h will heat the house for the evening. With TRVs set at 20 degrees I see occasional min temps of 17 and max of 20 with this regime over the 24h period

3. At 5am (and 5pm) the UFH turns off and the thermal store will come up to 50 degrees and just hold there - hot water is then on demand for the useful times of the day.

To be clear I dont change any settings at the level of the GSHP - its all regulated by my on/off timing controls at the heating manifolds. This strategy defies the logic of 'always on, low and slow' heat pump use but in our case leads to effective and efficient home heating & DHW  - I have no idea what my SCOP is (not reported by the unit), but the combination of cheap night tariff, battery, PVs and only running the UFH as described works well for us. 

Hope that helps - happy to provide further details if useful

DelT  

The first thing that I would question is the size of the heat pump, is it adequate for the heat loss of your home? What are the heat loss calculations for your home? 

I have got heat loss calculations for the house which say a total of 3.8kW for all rooms, but I think this is ok as the central heating is currently running very well and the cost seems pretty reasonable to me.

How much thermal energy does the solar collectors produce?

I don't have any info on the collectors I have that I can find, is there another way to work this out?

Operate the heat pump at a fixed Leaving Water Temperature (LWT) of say 50C, to heat the water in the heat store sufficiently to provide hot water.

I think this is similar to what I was doing when I asked the heat pump to maintain 50 degrees in the thermal store, but that turned out very expensive.

My suggestion of operating with a LWT of 50C was to help provide hot water without having to make any physical changes to your system.

If you find that method too expensive to operate, then @heacol's suggestion of separating the heating circuits from the heat store and then using the heat store as the supply for DHW heating I do believe would work, but the solar collectors would only assist DHW production and not with central heating.

To fully use the solar collectors for both CH and DHW production would require the addition of a separate DHW cylinder along with the three port diverter valve.

I would suggest that you read the manual for the Resol solar system to see what information the controller may provide.

If I was to stick the valve in to separate the heating and hot water, do you think it would be worth trying to link up the solar collectors in any way to supplement the heat pump?

I have got heat loss calculations for the house which say a total of 3.8kW for all rooms, but I think this is ok as the central heating is currently running very well and the cost seems pretty reasonable to me.

How much thermal energy does the solar collectors produce?

I don't have any info on the collectors I have that I can find, is there another way to work this out?

Operate the heat pump at a fixed Leaving Water Temperature (LWT) of say 50C, to heat the water in the heat store sufficiently to provide hot water.

I think this is similar to what I was doing when I asked the heat pump to maintain 50 degrees in the thermal store, but that turned out very expensive.

I cannot comment on the size of the heat pump, as I do not have the details of your property. However, you do not need a thermal store as you have under floor heating, which is a thermal store. That cylinder can be changed in to a hot water only thermal store, with a good quality deserter valve, you will for a very small amount of work, and unfortunately a lot of rubbish, a well performing system.

Not is all lost.