JohnMo

Build a small wooden table and sit the second unit on it. Or get some neoprene foam to separate the two units, so you don't end up with annoying rattle in the future.

Do it yourself. The only way you will get a sensible outcome. Start with heat loss calculation, use the Jeremy Harris one in boffins corner. That will let you size the heat pump. Either download a trial version of LoopCad, design your floor loops, 150 to 200mm centres should be ok. I used Outsourced Energy for all my UFH parts, they do a design and install service, they should be near you. They supply all good kit. Ventilation treat as separate entity, it will just run in the background. If solar is available it will use it automatically from the consumer unit - nothing complicated needed. Same for the heat pump.

In that case its already taken care off. So will mine, but I heat it twice per day. So might others If it was rated at max capacity to match heat loss, it should be running full time.

Not fully correct Each bathroom is a zone. It has independent zones. Plus if running a heat pump, you comply with the section, where possible weather compensation is to be used.

Don't think it looks tidy. Don't like taking pipes under non structural walls either. All my pipes went through doorways.

If it 1.7kW it would be fine. If its 3.9-4.8kW obviously not big enough, then you are looking at a bigger heat pump. The JH spreadsheet is pretty close to reality, in my experience and our house. We are around 200m2, very poor form factor, (single storey, all vaulted ceilings, long thing building) not Passivhaus, we have a heat loss of around 3.5kW at -9 and a 6kW heat pump.

4kW heat pump would be fine. Go for something like a Panasonic. You will generally get some cycling, but that is normal. Then you need something else to heat the hot water.

Not quite correct. If you heat demand was 4kW and you install a 4kW output heat pump at your lowest design temp. The coldest day would require 4 x 24 or 96kWh for the 24 hrs. Now if you take 2 hrs to heat DHW you now only have 22 hrs to deliver 96kWh, so you have a short fall in available energy.

Keep it simple Get local plumber to install UFH on ground floor only (plus any upstairs bathrooms). Set ground floor UFH on 150 to 200mm centres throughout. Any bathrooms on 100mm centres due to less usable areas. Buy a Panasonic heat pump to suit your heat loss, a heat pump cylinder (any make) with at least 3m2 coil. Manifold for UFH, no pump, no mixer, a 28mm diverter valve. Self install or direct plumber and electrician. Use Panasonic controller as a single over temp thermostat, run system on a very small weather comp curve. Possibly starting at 15 Outside and 25 deg flow and -5 outside and 28-32 deg flow. Run everything as single zone. Provision with option to install electric panel heaters in bedrooms, but don't install unless you need them once moved in. Add electric towel rads to bathrooms use around 500W plus ones and get an external timer thermostat for them.

I wouldn't go through any block work, only doorways.

Not saying it's wasted, but it not enough to be properly useful. It better to have a slightly longer run, the remainder run time is all useful heat. Its getting the correct balance between heating stuff up and heating heating stuff up and adding heat to the house a few runs at similar average outside temps, only change from first and send two runs was a slight change to compressor stop hysteresis to get a longer run. The compressor start hysteresis remained the same 7.8 deg OAT, short runs (10 to 15 mins duration), 9.1kWh electric 44.2kWh heat delivered - short runs (space heat CoP 4.86) 7.5 deg OAT, longer runs runs (15 mins plus duration), 5.7kWh electric 27.8kWh heat delivered - longer runs (space heat CoP 4.89) slightly colder day at 6.8 deg OAT, again longer (35 mins plus duration) runs, 6.8kWh electric 33.8kWh heat delivered - longer runs (space heat CoP 4.97) On all occasions above is run full WC mode, house remains at a stable 20.5 degs. Difference between 7.8 and 7.5 deg day is a reduction of 40% electrical use. Which is huge. CoP stays similar, CoP increase on the 6.8 deg day, is due to slightly cooler day leading to longer run times and less standby time. As point to note I did find similar reductions in energy use when I optimised the gas boiler when running very low flow temps, once I added the heat meter and started to understand what was happening.

Good air flow would be the prime reason I suspect. Makes you think, a small box with the compressor, heat exchanger, pumps etc. to sit outside and a big external to the box condenser, if big enough no fan needed.

Sorry but are they fit for purpose as a designer. With LoopCad (UFH design tool) you can easily match heat demand to the amount of pipe in the room. Or you can install more pipe and balance the flow rates to get correct room temps. It would appear their design is basically bounce room temps on a thermostat to manage room temperature. How are you heating the water, boiler or heat pump?

I have zero issues with the heat pump. A heat pump behaviour is different to a boiler, its output is a lot different. Most heat pumps are sub 10kW, most oil boilers are 4x the output. You don't have lots of energy, a 6kW heat pump running at full load for 10 mins generates a max 1kWh of heat. Getting 60L of water from 21 deg to 28 is 0.5kWh, plus heating a bunch of pipes, a heat exchanger etc. That 1kWh is very quickly consumed, before any real useful work is done. So a typical heat pump running for 10 mins looks like this Key points are Compressor starts at 22.5 degs return temp At 10 mins the flow temp has increased to 28.6 degs and return temp is up to 24.8 deg. Actual heat output after 10 mins is only 0.852kWh, so basically heating the system, and not much heat is going into the house.

My heat pump instructions state The choice of regulation is fundamental to optimise the efficiency of the system and to reduce the number of starts/hour in order to achieve the correct thermodynamic balance and the correct lubrication of the mechanical parts in the compressor, it is recommended to choose them in order to have a continuous operation of the heat pump of at least 10 minutes. Found with mine, running less than about 10 minutes, result in the best part of no heat being added to the house. So it is now set to run no less than about 15 minutes. Short running is likely to use lots of energy and not do much heating of the house. Especially when the heat source is located outside.

How many kWh you should use per day, has many variables. Insulation levels, house temp, outside temperature. Plus exactly how you operate the system Some givens A fixed flow temp will increase your consumption on all days except the coldest days. Stop starting the heating will generally not help. A buffer of small capacity will not help Mixer valves will not help Small cylinder coils will not help.

Shelly H&T. Gen the usb version than it stays plugin without need for batteries.

No, as I have a battery, charge the battery in E7 period and generally run the house all day. Heat pump is on WC, but as the temperature is naturally lower over night most the heavy lifting for heating is done without any intervention from me during E7 times. ASHP will run a bit during the day, but not that much. So a high proportion of electricity is either PV or battery not that much high price electricity.

No just a smart meter, to a single CU. No split circuits.

I am just using E7, which should already be pre programmed into the smart meter.

Think you answered your own question

It may well be. You have to switch it all on and come back after 6 hrs. The crankcase is heated to take the refrigerant out of the liquid phase, in the crankcase where it dilutes the lube oil, and kills any lubricating value. If you still have an issue first thing tomorrow, it something else.

But to be meaningful you need to operate your heating system in a similar way to how you operate a heat pump. Otherwise a good chance of rubbish in-out. Rules of thumb can lead to big over or undersized heat pump, neither are good.

You really need to complete a proper heat loss calculation. Start from the basics and work from there. You need to spend a couple of hours heating hot water, so then that leaves 22 hrs to supply the house with heat on your coldest design day. So for example a heat loss of 4kW is 4x24hrs, so 96kWh, then divide by 22 hrs, which is 4.3kW. You then look at the heat pumps datasheet and if your design temperature is -3 you choose a heat pump that can output at least 4.3kW.

No tool to make joint, so just about idiot proof. Just slide pipe in, done, nothing to twist or lock. Also they use thin metal pipe reinforcing at each joint. They do use a tool to allow the joints to be stripped apart.