JohnMo

Just got to read the number of issues people have in a ASHP section of this forum, with rubbish CoP. Bit like car manufacturer MPG claims, real world isn't the same a laboratory conditions. You can get great CoP figures, until the owner or installer, starts adding lots of zones, controlling temperature via thermostats, buffers (of poor design) to compensate, immersion heaters, etc. An arbitrary figure of efficiency saying your heat pump has about 2.6 better than a gas boiler (during the heating season) is probably good enough to cover the good and bad install.

Mine gave the following for a named gas boiler in my as built - Efficiency: 89.7%, Even though I was running at 35 degs max flow temp, against a declared heating efficiency from the manufacturer of 109.7% for the same running condition. Checked against certified heat meter and actual gas consumption, I was getting very close to that figure. There just numbers to enable a comparison of one building to another on similar basis, at the end of the day. Move on to the next battle.

Not sure you are looking at that correctly, the difference to compare is extract temp from the rooms (internal house temp), and that being resupplied to the rooms. You need the room supply air temperature, to be as close to the extraction from room temperature as possible, otherwise you are pumping in cold air - this should be a small dT into the points of degree difference. Supply temp to rooms / extract from the rooms.

Well, multi foil only functions with an air gap, so not really that thin. Aerogel is major expensive and only performs about 25% better than PIR. So 10mm Aerogel is about the same performance 13mm PIR. Cost ratio is about 10 to 1 comparatively. I would just use PIR, readily available and way cheaper. Or battens and mineral wool, attach plasterboard to the battens.

Everything you need if you can be bothered reading STP11-HP-01_Heat_Pumps.pdf

If your running lots of zones on thermostats why bother with WC, you may as well simplify and run a set temperature. Or do WC properly and set the thermostat as limit stops, not temp controllers. I would, and did, dump all the zones and use a single 0.1 hysterisis thermostat for the UFH as a single zone. I can still get a 0.5 Deg swing in temperature, which you can feel.

Perhaps cheaper to add more insulation so your overnight demand reduces

That's good to know, looks like I have made a nice cosy spot for them. No wonder they love it.

Have you tried batch charging the floor. Run heat at a higher temperature so it buffers heat in to the floor and then releases like a storage heater when you switch off the heat pump. You can do this the following way

Hi, do you have concrete in the floor, or is it just wood above the heating pipes?

If you go into the trade section there is a full spec. U valve for the window appears to be 1.4, which is, standard building regs.

+1

Some success after reading @Bramco reply on another thread. Sort of using what he does to batch charge, but have a longer run time to keep the fan coil happy so have batch charge curve based on outside temperature, the batch charge lasts for nearer 10 to 12 hrs depending on outside temp. So now have the heat pump set up to run and chase a slightly elevated temperature, with floor acting as huge buffer, so getting long run times, which in turn keeps the fan coil happy and charges the floor in a single run, heat pump is not having to modulate much. Leave it run a few days then assess if I should dump WC all together. The flow temp today got to 31 and the house thermostat tripped the UFH off at 20.5.

UFH pump pulls through the mixer valve. Doesn't need a buffer in the system but can if you want. The low loss header installed has a pump on the central heating side, so different to elimination of LLH and just using the boiler pump. I run with zero hydraulic seperation and mixer valve and pump on UFH without issue. Have also run direct from heat pump and boiler without mixer and pump, again no issues. If you have all circuits of the UFH running with actuators, you need a bypass, or simply make some circuits always open whenever there is a call for heat, such as bathrooms which can never be too warm.

Question, do the dips coincide with the unit being on boost? If it does the boost flow rates could be slightly out of balance. Or do your filters need to be cleaned or replaced

How can you have 20 dT requirement when you are only flowing at low temps, the boiler would be expecting a return temp lower than room temp - that cannot happen. Example flow of 30 degrees how can you have a return of 10 when the room is at 20? A boiler capable of low flow temperature isn't designed like that. 20dT is old hat for high temp boilers only. Example - My Atag never looked for 20dT would just modulate the pump the get the dT it wanted to see. At low flow temps would modulate the pump to around 7dT, that was the dT you had from the boiler. Again not sure where you get one pump, there is one pump in boiler and one on each manifold. 4 manifolds and boiler pump. Get rid LLH, no mixing going on there, flow around 32 into the floor, 42 from the boiler to allow for mixing manifold mixers. If you wanted to get dT20 you just run at dT 10 across the floor, boiler return is 22, efficiency about as good as it gets.

A sip sounds good, but, you still need a block work outer skin and additional insulation. How much of the work do you want to do yourself? I did 195m² for not much than your quoting, finished. Very much a hands on ICF self build. I would be tempted to drop both the sip and ICF idea. I assume your in Scotland as it mentions warrant. 2 options I would look at Larson strut, stick build on site, cellulose filled. Block work build with external insulation. Use local labour for both options

If you run out of water 4 things to do Heat it hotter - needs more cold water to mix down to correct temperature - increases the effective volume of hot water Heat it more often - let it heat when it needs, to little and often. Reduce flow at outlet or time used, your using to much water Get a bigger cylinder - your cylinder is too small for your lifestyle or number of people in the house

Early start early stop with UFH just doesn't work, the algorithm is really designed for radiators not UFH. Same as load compensation useless with UFH. Never achieves the correct temperature at the right time. Tried it with Atag controls and Salus.

The difference between a LLH and buffer is purely volume of water it contains, both provide hydraulic separation. A volumiser is inserted in the flow or the return and is there to provide volume only, it does not provide hydraulic separation. With hydraulic separation you have to have a pump either side of the buffer or LLH - one for the boiler and one for CH and/or cylinder side The big pump is there because you have a LLH. Remove the LLH and the boiler pump will do the pumping. Trouble with WC is they have a glacial reaction time due to the low flow temp. You may be better setting to 20.5 except a set back period of 19.

Cascade MVHR yes. No heat recovery, but do not exchange air when not needed or do so at a minimum rate. Tickle vents open and close based on humidity levels.

Not sure the open thermostat one would have worked for you, as you have so many zones and suspect most will be open and closing UFH manifold loops. An opentherm thermostat would really only be any good in a central area doing all the heat control - single zone. Weather compensation You have a bunch of thermostats already installed and connected to your manifolds and mixers and pumps. The mixers will limit the lowest flow temp from the boiler you can use as there will be around 10 degs of mixing going on inside the mixer. My suggestion is to keep it simple. Leave UFH system as is, with thermostats etc Move boiler to 4 port configuration Get rid of the LLH and replace with a small volumiser say 20L that should fit in the same space as the LLH. The volumiser would be in the house heating circuit only. Remove the big secondary circulation pump, as not needed anymore Run heating at a fixed flow temp (not WC), but run way lower flow temp than it's run now, say 35-40, but run for much longer. Nearly all the benefits efficiency wise, easier to implement, your wife will not be asking why you bought all those thermostats.

Why limit yourself to MVHR, dMEV or MEV done well can be equally effective. You need to it on a humidity controlled basis, with humidity activated inlets, either trickle or through wall. The other option is cascade MVHR, very little ducting used, which is a little like PIV and MEV combined with heat recovery

I would say, any sun is bad, when heating is expected to be on - who cares about summer sun your heating is off.

Here is a thread I started prior to doing my ground array. Approx 4kW split into two. No way it would 60m without a voltage drip too big or huge cable. Ended up doing 4x6mm2 armoured cable to inverter, approx 60m away.