JohnMo

I would doubt it actually does anywhere near that. It may say that on the box, but most intermittent fans are just noise generators. Our last house said that, but when I put some tissue over the inlet it fell off. No suck going on. MVHR, mine very rarely goes in to boost these days, no steam buildup. Even if it does it's gone very quickly. When first installed on a new build we would get the MVHR boost quite often. After first year, almost never goes into boost.

Sorry to install a heat pump and cylinder to an existing UFH system - £13k - they are taking the p#ss Panasonic heat pump £2500, cylinder around £1k. Sundries £1k Or contact Cool Energy, they do a self install scheme to get the grant. They design, you install, they commission. Allows you or you plumber and electrician to install. They have a new 6kW heat pump also.

If you don't need to run I wouldn't, if your wanting or needing heat then run it.

The more air you take into the house that is cold and heated up (MVHR heat exchanger, heaters) the dryer (low humidity) it gets. This normally balanced by humidity generators (people, showers, general life) the bigger the house the few the people per m² the bigger the issue. We are down to about 40% humidity after a few cold days. Got down to 35% last year. My first quote for MVHR was £10k, ended spending closer to £2k

Go to building guidance notes, for MVHR and the rules are there. Plenty of posts on here also. Your trouble with a big house is going to be over ventilation. Big house needs big flow rates, a few very cold days will drive humidity down low, if you are not careful. Those prices are daft, but you are building a mansion so you get what you get. Hope you end up saving £350 in heating costs a year, because thats what you are paying just to buy the MVHR over 20 years. Two units (what we have) can make install easy with way shorter runs, but two sets of filters to change each time.

More than enough to kill you and few others, if you have the hoop stress calculation wrong. Hope you did hydrotest before allow steam in the system.

Trouble is if you have a heat loss in the property of 2kW, you then require 48kWh for 24 hrs. To deliver that in day 7 hours needs 7kW input. If you had a 4kW heat pump you need 12 hrs of running.

I really wouldn't bother chasing the lowest possible temperature, you just going to end up with heat pump cycling. I could run my boiler at 36 degs or below and it cycled every 6 minutes on then off. 6 mins on, 6 mins off. The lower I went the shorter the cycle. Raised the temperature to 40, would run all day every day, never cycling on or off. Just steady running flow temp varied by 0.2 degrees. Same is true with heat pump. You need a differential between flow temp and room or you cannot dump the heat quickly enough. But as said above 100mm centres and radiators is a bit of a waste of time. You may a well do 150mm centres and have an easy life. No do a single zone, I would be trying to single zone the whole house and then run weather comp. If buying again I would look to go out and just buy a Panasonic R32 monobloc ASHP.

Are you using all three phases? Or just one in the house? 2. Our is in plant room. Some have them outside. But as temperature drops so does the battery output. Some will have inbuilt heaters. So you would need to check. 3. If it's a DC battery you need an inverter. If it's AC coupled they are already built in. 4.we have givenergy all in one, it generally provides the whole house straight out the box. Battery size and tariff. With heat pump running in cold weather the battery soon gets depleted. Charging slab in cheap periods is fine but once you get below zero, expect to charge in the evening also, otherwise it's a slippery slope of ever depleted slab energy over a few days. Then you end up running the heat pump for a lot of hours to catch up.

Just wouldn't bother with a low temperature UFH system. As room temp rises the floor output stops as soon as floor and room temp match.

The check valve you show at the left hand dashed box

Are putting any heat loss calculation into this design? What is your W/m² output target? Are you investing in suitable insulation below the pipes, i.e. 150mm+ of PIR or 50% more in EPS? Is screed or something else going above the pipes? A quick look at 100mm centres and a realistic heat pump flow temp of no more than 40 degs, you are looking at 62W/m². 50mm centres closer to 70W/m² 150mm centres is about 57W/m².

Blauberg? Just about any ventilation supplier.

On paper looks fine, 5 year warranty - but How much are filters to replace? You need to look things like that. Do they require an approved contractor install and commission to get the 5 year warranty? Is there UK technical support? Do need modbus and WiFi connected? My opinion no, install, commission, forget (except servicing). Do you need CO2 response? Not really. I would look a Titon also, UK made, UK technical support, good solid unit.

Are you getting a grant? If so get the installer to do the UFH, it is all part of the grant allowance of £7500

Do a spiral - not a zigzag. Or you do an oversized bend and bring the pipes in. Why do you need such tight pipe spacing?

Not sure I would use a smart thermostat on any boiler. Smart really just means internet connectivity, generally they are just dumb on off devices. If Baxi have a controller use that.

You need to look and see how things connect in the cellar. If the lintel is connected to another cold source (e.g. wall then floor), the lintel will stay cold no matter how much insulation you put under it. So you may need to install insulation in house floor instead. 25mm (or more) under the floor finish would make a big difference.

Possibly will, but the kWh used, no matter if UVC or Sumamp would be pretty much the same on a daily basis. You have more flexibility with an UVC, you just heat to different temperature, to alter capacity. A Sumamp has defined max capacity based on PCM melt temperature, so less flexible on that basis.

EER/SEER is cooling, CoP/SCoP is for heating. Why would you design a system around 18 Deg house heat temp? Way to cold. Suggest you are over thinking the whole thing. Calculation of heat loss is needed, but that isn't difficult. Add 10% for DHW and/or defrosting, which generally occurs between +3 to -3. Design to cover 99.8% of likely outside temperatures. It is unlikely the heat pumps on offer, will exactly match the kW required exactly, so you choose the one one up. Cycling isn't an issue generally and the worst can be fine tuned out. Most issues with A2W revolves around distribution system in house being split into many zones, poorly installed and designed buffers and way to high a design flow temperature. Then home owners ignorant of how to operate and wanting to operate how they did with a gas boiler. Most these issues are not relevant A2A as the equipment and how it runs is factory designed and set, and the home owner cannot mess with it.

PV is cheap, batteries aren't Actually PV including mounts should be around or less than £200 per kW. An inverter to support couple of hundred pounds.

I doubt that, as you have a heat meter so will pay by the kWh.

But it is unlikely you would ever have to replace the whole contents. Thermostat is low down, the rest of the cylinder will be at a higher temperature. Bottom of our cylinder can read 12 at the thermostat, but it's actually 45 at the top of the cylinder. My average input to a 210L by immersion is 4.5kWh.

Our houses at a very stable temperature, but there are some days that it just feels cooler. We had the fire on yesterday. Small load to get it started, then one small log. Burn was about 3 hours on very low. Soap stone gave off heat until bedtime. Small log shed would keep us going for a couple of years.

Call cool energy they will open now. Have you tried switching the whole lot off and on?