JohnMo

DHW, Domestic hot water - Heating your cylinder.

So was your first photo showing the heat pump showing 47 degrees flow temp, on DHW heating, as it does not be match the heating curve?

I would agree with Dave when installed pre heat exchanger it's there for frost protection of the HE, not for heating the house. Post heat is for heating the house.

First observation is the flow temp is high at 47.8 from the heat pump. Do you know what your UFH flow temp is, or does your floor heat up quite quickly? If you could reduce that flow temp to about 35 you could gain an additional 1 on your CoP from low 2s to low/mid 3s. That could save 10kWh a day! My flow in the floor is 29 as a reference, it's -7 here, house sitting at 19 inside.

Also from the photo the flow rates look quite low. You may be better with a higher flow rate and slightly small DP across the loops, this would give more energy to the floor, you then reduce flow rate. Option to look at later. On the night set back, only drop it 2 degrees, then the boiler isn't having to work so hard to recover floor temp. But just alter one thing at a time, understand the outputs before changing something else.

Just looking at the dotted line on your graphs, which looks to be the thermostat set points. And the red part where it states heating is on. A couple of observations based on experience with my house. You have the heating on at various times and various temperature throughout the day. Looking at the red parts of the graphic your room temp is just about getting to temp and you switch it to a lower temp, then a few hours later a higher temp. So with floor inertia you boiler is playing catch up all the time. The other thing that may be happening you have multiple zone all programmed at differing times of the day. This is great, but in practice, you can have periods where you only have the lounge switched on, so the boiler is only being asked to do a couple couple of kWs of work, but the boiler may have a min output of 10kW. In practice this leads to the boiler short cycling. So boiler starts, a few minutes later trips on high return temps or minimum flow. Boiler is locked out for 10 mins, and this repeats until more zones are opened up. So why does this lead to poor heating performance and high consumption of gas. Short cycling, every time your boiler starts, the efficiency is low, it's heating a slug of cold water and lots of metal, once the boiler has been running for a 5 mins the efficiency climbs quickly. Continuous on off cycle means the boiler is in a low efficiency mode, the 10 min lock means no hot water is being pumped around. Timing efficiency, your floor is heating, you can see in the lounge at about 10am a big jump in temperature. So big it look like the flow temp is way too high. My recommendation as a trial, set all your thermostats to manual at say 19 degrees, and the boiler will have the whole UFH system to heat, see what happens. I suspect it will be fine and heat up quite quickly. If the temperature overshoots 19 then your flow temp is too high.

The thermo conductivity will be 0.044 that does not change. If you compress it, it's still 0.044, or could argue it may be worse as you close up air spaces in the insulation. Overall the compression reduces the R value. R value comes from the property of the thermal conductivity (0.044) and the insulation thickness (200mm).

Most thermostats are pretty rubbish. I am using Salus thermostat wg610, I think, that is set at +/-0.25 hysterisis and that is pretty rubbish due to time it takes to move room temp with UFH. I found getting the flow temp right is the most important thing. A couple degrees either way from ideal will cause under or over temp issues. I currently have my thermostats setting moved out the way. And pretty much fined tune the flow temp based on outside temperature. For me 31 to 32 is ok sub zero and 25 to 26 at about 10 degrees work pretty well. These are the best I've seen for hysterisis. Q7RF-Manual-EN.pdf

A few questions Whatis your UFH flow temp? Are you doing a fixed flow rate or weather comp? What is the ASHP flow and return temps? How big is heat pump? Do you know your heating design kW? Does your system have a buffer?

You don't want it to low, do you need to include accessible door thresholds?

How much system water volume do you have at the moment, actually open to the heat pump, do you have a buffer? If there enough volume of water to allow the unit to defrost? Compare that to the minimum install requirements, before you talk with them as they may ask. If you answer incorrectly you risk voiding any warranty.

A a slight reality check, we are also around 190m2, but single storey so more exposed surface area to the outside. Also we hit -9 a few days, but generally we are putting 60 to 70kWh in to the floor measured by a heat meter. So if you are getting a CoP of 3 ish, your are in the same ballpark. (20,000W/24hr)/190m2=4.4w/m2 Multiple by you CoP say 3 at low temps. 13.3w/m2. So still as good as a passivhaus needs to be. It's just cold your house heat losses more heat.

Are you diverter valve(s) opening correctly. Not sure if you 2x 2 way or a 3 way? Sounds like there is a blocked flow path? Is it ok in heating mode?

When you say vents in the rooms, are these internal ones or external? Do you have extract fans? Your minimum require for fans would be an intermittent one in the bathroom or shower rooms. You would also have a extract in the kitchen either stand alone or via a cooker hood. Next up would continuous running ventilation, dMEV or PIV. Then you start getting in to MVHR.

I thought it may be easy to go back to calculate the u value, but when you start thinking, ventilation rates, MVHR recovery rates would need to accounted for. Did you get solar gain, did you have the oven on, bit of a pain, so stopped thinking about and decided to write the above instead

Most of Sweden and Norway, plus other cold countries could just be on WC with a small nighttime setback. Most these surveys are rubbish data in and out and most likely suit an advertising drive at a point in time. But most of UK are based on on/off controls anyway.

Half way down on this thread makes interesting reading on Tado, especially the UK version of their control system.

Being on TV? There are plenty of other with multiple whole walls of glass, where it make you wonder how the calculation adds up

Grant use a heat pump made in Japan by Chufu, and generally simplify the install and make an S plan system, the same as a gas boiler would have. Basically to make it simple for a bog standard plumber to install. They seem happy to stuff a controller full of good features in an in appropriate place. If you are switching to UFH make sure you do it fully informed, doing it badly will make it very expensive to run due to the downward heat losses. Post a specific question with all the information you have such as proposed floor buildups etc. Other than that is the Grant heat pump good? I am looking for a heat for cooling more than heating, but when installed will do both. (a feature the grant heat has but they tell you about it)

Installers want to in and out asap, so set everything high. So you are trying to set weather compensation (which they seem to call water law) from the looks of it. Any figures you have seen are applicable to someone else's house are very unlikely to apply to yours. Basically you are trying to balance heat loss with heat input. If you leave the water law (201) set as per defaults, the heating will start at 15 degrees and keep increasing temp until the outside temp gets down to -10. This all sounds ok for a starting point. So I would leave these as is, unless you know you don't have the heating on until the average temp outside is say 10 deg. If so set to this figure. Then at with the default setting (202) at 15 your heating flow temp is 25 and at -10 it be 40 deg. So if you set everything back to those settings - ignore what the rads feel like. Move all your room thermostats up to about 24 degs, so they don't interfere with anything. Does your room get up to temp, at low temps it takes a while, so leave until tomorrow. Now if your main room is too cool increase 202 high figure a couple of degrees. If too hot reduce a couple of degs .... repeat until happy. Once happy with your main room, are other rooms how you want them, if not you will need to balance the rads to suit.

why dump water just pull out the thermostat? or thermostat probe

Some reading material 679346837_AccumulatorsBuffers.pdf

At the moment you have the two cylinders in parallel, could you do them in series. Also you are setting it up for rubbish flow, as the system has no head available - couple of metres only. A thermal store will give you mains pressure, UVC the same. For the thermal store you need a huge coil 6m2+ or tank in tank to be efficient for DHW at heat pump temps. You also need a pressurised thermal store/buffer for a heat pump to allow direct charging. You can get split thermal buffers, stores, with two operating temps designed for heat pumps and stoves. Off the shelf solution, but tend to be a big capacity Some ideas here also https://originaltwist.com/2019/11/26/heating-system-for-heat-pump-2020-revision/

Some light reading Atamate_SDAR+Paper+2019+(1).pdf On MVHR, we used posi rafters and strung the pipes through the gaps. We also made good use of coanda effect terminals.

I can remember the days, an airing cupboard with a copper vented cylinder - no insulation to be seen. If the buffer was in the shed you worry about wasted heat loss. The energy actually saved by a buffer by letting the boiler run for decent time should not be under estimated. Now in a position to compare the effects of having and not having a buffer, now have a heat meter installed and all the usage figures of gas, as referred to above November 2021 compared to 2022 average daily usage of gas was 20kWh per day lower in 2022 than in 2021. Efficiency of gas to heat conversion in 2021 was 61%, this year 98%. (although I said 95% in an earlier thread that wasn't correct)