JohnMo

I live in NE Scotland, we have days at a time at -9 without a preheater (never bothered to install and zero issue. Enthalpy exchangers - we don't have them either - our lowest house humidity hit 37% and we average just over 40% in the heating season. Not sure you really need them.

Couple of things jump out, floor area Degree days, is huge, they are treating the degrees like a 'normal house' If it's MCS, they will always ignore MVHR and apply Thier own room air change rates - the system doesn't account for any other than the normal.

We have a single storey with carpet and UFH in the bedrooms, but it's not very effective doing low flow temps. But ok if you like cooler bedrooms. Thing is though with a well insulated house open the bedroom doors for 30 mins and they are the same temperature is the same of the house. Many on here just don't have any heating in bedrooms when upstairs. Lounge carpet not a fan with UFH. I thought the same with the summer house (very well insulated) but that never got warm when it was cold outside. Fan coil and I can have temperature I want.

Yes, has an inbuilt timer, I did just that a few weeks ago as a trial.

The Runhu diverter is the same as mine, from Cool Energy. Works well. https://eco-outlet.co.uk/products/cool-energy-solar-power-diverter

For the DIY'er the best thing since sliced bread. Tectite Classic can be taken apart and remade several times without issue (slight cost increase), sprint one use only. I like that once made up the joint can be rotated. I've used loads , had one leak due to the copper not being inserted square and it didn't push home correctly.

Make sure you locate it below the top of the cylinder so the hot pipe comes out of top of the cylinder and then downwards as soon as possible for at least 150mm. This will form a heat trap and stop a circular flow of heat within the pipe, which slowly make the cylinder cooler.

Loctite string is favourite at the moment.

I did this most days on our build, had loads of rain. I found the quickest and easiest was actually a dust pan, scoop and throw over the stub wall. Or into a big bucket.

I did a single hot run of plastic from plant room (UVC) to utility room where cold manifold is (very central location), located both manifolds there, then plastic to each wet room. Wetrooms are a mix of plastic and copper. Cold pipe was in conduit under the floor insulation cast into the concrete slab. Hot is in the roof insulation.

I did a manifold and then one supply of hot and cold to each wet room in 15mm, then branched once in the wet room.

Not sure if this an option open to you, but our cold water feed came into the house in a 100mm duct, up through the foundation. I used the same duct to take the outside tap pipe through, the sealed it off.

I have messed with WC on UFH for 2 years, the truth is you really don't need it. A good mixer valve like an IVAR is all you need. Have WC for the rads. I have a standalone ESBE mixer and controller they are good, but stupid expensive. Mine is there for a specific reason, not normally needed. Then as suggested above normally closed 2 port valve for the cylinder and normal open for the heating system, when there is a call for DHW heating the 2P valve opens and the others shut. Boiler to high output. Not sure you need to do anything else. Anymore looks to be for zero gain. Normally open 2P should just be an actuator change.

DHW, I tried various way to be smart, but found letting it sort its self out, worked best. My heating regime is simple Heat house and summer house first. This uses E7 and battery and solar if available, DHW is allowed to heat between 12.30pm and midnight via the ASHP. On a dull day heating DHW tends to be by ASHP, bright day like yesterday all DHW was heated by solar diverter. Solar diverter to DHW only when the battery is charged from solar. This just picks up export via a CT clamp once battery charged.

With my 6kW, I just batch charge the floor, I run my ASHP flat out, can run 7 hrs straight no issues. Have a target flow temp of 35, knowing it never get above 33 before the thermostat switches it off. Not the best CoP, good enough, on cheap rate, so still cheaper than gas. Various ways to get around size issues.

Don't waste your money, the switching threshold (hysterisis) is 0.5 at best, 3 Deg at worst - just get a Computherm Q20RF or Q7RF from Amazon for £60 or less the Q20RF is nicer to use. No zone valves or actuators on the manifold, if you have radiators, get an IVAR low temp mixer valve with pump, and drive the pump on and off with the thermostat. Just shows they don't know much.

Works no problem, I even have 300mm pipe spacing, 100mm concrete and again no issue. But they are a bit of a learning curve. Few things I found through experimenting, you need to be aware of. Changing floor temperature and house is quite a long process (many hours), so a normal thermostat is just rubbish and you get big under and over swings. You really need to use a 0.1 Deg hysterisis thermostat. You cannot use room compensation as the algorithms cannot cope with the long reaction times. Don't bother trying to do temperature setbacks, they generally don't work the way you expect. You cannot switch the heating on at work and hope to have a warm house when you get home (unless you do when you arrive at work). There is zero point zoning, run as a single zone. Two options of how to operate, charge the floor and use like a storage heater, or continuously feed the floor at a low temperature. I have done both and they work equally well. 5 degs difference in flow temp is the difference in the two methods. I am on E7 with ASHP, battery and charge the floor at 33 degs (overnight), for between 7 and 12 hrs depending on outside temp, automated with a timer thermostat. Generally it takes another 12 to 18 hrs to cool enough for the heating to come back on again. The wife was quite shocked the other week when it was near freezing outside (6pm) and I told the heating actually went off at about 10am and was not coming back on until after midnight. You can't do that with 50mm screed.

I know when I was running a boiler last year (Atag A325ECX), the flow temp was set to 36 degs, the pump speed was being modulated by the boiler and it set the dT at about 6 degs. This also coincides with the part load performance data on the datasheet (30/36). But also think min modulation kW allowed is also considerably higher than the 50/30 flow temps. Think it must try to keep the return temp at 30 and above, but just reduces the dT to accommodate a lower flow temp set point.

Fundamentally a heat pump runs as detailed below 1. you or it sets a target flow temp, depending on fixed flow or a compensated flow temp. 2. Heat pump starts and monitors return temp and delta T 3. First it maintains delta T, so if you have a target flow temp of 40 and delta T of 5, but the return temp is 25, it will flow 30 degs until the delta T reduces below 5. As the delta T reduces the heat pump add more flow temp until it gets to 40 degs, while maintaining the delta T. 4. Once at 40 degs the ASHP will modulate down from full power to a lower setting to maintain, 40 deg and the delta T. Two things cause a slow ramp up, the heating system has been off for too long, or you are trying to bring temp up too quick. How exactly do you operate the heating? Do you have a buffer, if so how big? How long does the DHW heating cycle take? How many loops of UFH do you have?

Sounds rip off, my Triton fan/motor was £276, incl vat and delivery. I thought that was expensive.

Looks to be a split unit and only the outdoor unit being provided. You will need a refrigeration engineer to install also.

I would just go elsewhere for a quote. I have panels on a hill 70m from the inverter, it's then another 20m to house, plus panels on the roof again about 15m to the inverter. Mine are all coupled to a GivEnergy All in one. Works great.

Was driving the UFH from a heat pump, and flow temps needed to be higher than I was prepared to run. Now use a fan coil, way better.

Not sure about that due to contamination for later use. Plenty of cheap cylinders on gumtree.

More like flow temps in the 40s, I had some in my well insulated summer house (now ufh decommissioned because it was rubbish), high 30s flow room below 16.