JohnMo

Depending on the controller it may be configured as the master thermostat unless it's just a time switch. Your sitting room maybe has no zone control it's just an open zone. The controller may be asking the system to do stuff based on what it sees in the garage?

The installation I am talking is simple. You will need a room by room heat loss calculation, then size emitters to room heat loss at same flow temperature. Direct cylinder with immersion timer. Set timer to any low tariff periods. ASHP, outside unit power cable via isolator switch. Two core screened cable between outside and wiring center. Power to wiring centre. Controller within wiring centre. No room stats. That's it no need for 2 port or 3 port valves.

Pipe sizes are simple for a heat load of say 5-6kW, I would just run 28mm until pipe splits for downstairs and upstairs then 22mm to each manifold. UFH pipes 16mm, and rads from manifold 15mm

But I would just delete all the zones, it's just going to make your heat source cycle and use more energy anyway. Zones add no value

Where is your boiler controller is it the sitting room?

So assume about 188m² (can't be arsed converting ft²) so 5kW sounds high. Would have expected 3 to 4kW. You can go grant, but by the time you're adding the MCS markup you will paying out as well. PV just couple to a 2x mppt string inverter. At a later date this could have an AC coupled battery added without touching much on the solar side. Or hybrid would replace the inverter. A 6kW Hiaer heat pump is £2100 including vat and you need to add a wiring center and controller for £550 Inc vat. It will modulate down to 1.6kW. (the 4kW down to just under 1kW) Sling in a direct UVC and run DHW from immersion (off peak), heat to 60 degs and install a smaller cylinder. Run UFH and radiators at same temperature, all one zone. Simple install, minimum materials, cheapest to run. Makes wonder - I would just ignore him and don't get him anywhere near your install. Don't bother with the grant, not worth the hassle and fighting over someone saying you need a 10 to 12kW ASHP.

All depends on modulation and demand. A heat pump that runs without cycling will always be more efficient than one that cycles. First a heat pump that doesn't need to cycle can run a lower temperature - mine I am looking at 5 degs cooler at 8 to 10 degs outside. That's a big chunk of CoP increase. Then there is the needless heating of big chunks of metal at the start of each cycle. So basically I don't agree, unless of cause the large heat pump can modulate down to meet the 7 to 10 Deg outside temp with undue cycling, then there is just capital expenditure and large pipework etc to accommodate it. Cylinder heating isn't a big issue, 210L from an indicator temperature of 6 degs only takes 50 mins with a 6kW heat pump to get to 50. Heat twice per day, no real impact on house temps, one heat is likely when your asleep anyway. I have actually found heating by immersion has barely changed overall electricity consumption. On paper ASHP heating gives me a CoP of 3, but in practice the immersion does a good job, maybe due to the long pipe runs on my install.

If you treat as vented you may not or wouldn't have an expansion vessel, inlet control group, or PRV. A unvented cylinder is just that, once installed you have zero control what the home owner will or not do. The rules at least make sure that at install stage, a basic set of rules are in place.

still don't agree, one rule for all appliances, then you don't someone deciding to fit an inline immersion or adding a gas boiler later and then blow their house up. If you want vented rules install a vented cylinder, if you want unvented then G3, simple.

Too many heat cycles to keep it reliable without regular replacement. Plus some numpy would see a hole in it, and replace with some random bit of metal from the shed.

Absolutely out of date nonsense. Just bought an ASHP that does 80 Deg flow temp, unassisted.

A service is supposed to test stuff and then fix and replace items needed. A standard item is test glycol and top up as required. They are also supposed to clean the condenser (finned heat exchanger you fan blows through), clean the casing, inspect expansion vessel pre charge pressure and top up as needed. A cylinder that has got a defective expansion vessel should not be put back in service, as the expansion vessel is a safety item, and be an item to fix asap, as the home owner would no longer have hot water. If you took your car for a service and it came back with a service invoice stating your oil and filter needed to be replaced, and you will need to book that in as it's additional cost, you would be well pissed. That is the service level you have just experienced with ASHP.

The first I found - 17mm deep, there are loads on the market. The bigger dia ones are way better than a 101 small ones doted about everywhere. https://www.simplelighting.co.uk/6w-circular-led-panel-120mm-diameter-warm-natural-cool-white-led/

Change the design of down lighters, you can get them sub 20mm if you want. Make life simple and not complex

And we currently get most days supplied by wind already. The more wind farms the better for me. At least the tax payer isn't paying hand over fist for decades while generation sites are built, unlike nuclear, which then gobbles up money for the next 100 generations managing the waste and securing the site that cannot be cleaned and stays irradiated.

Mine is Proctor Roofshield Standard blurb The Roofshield breathable membrane is unique due to its patented melt blown core and its three layer nonwoven spun bonded polypropylene construction. It has been designed for use as a pitched roof underlay that is fixed beneath the slates and tiles. The Proctor Roofshield breathable membrane will provide you with a secondary barrier to wind, rain, and snow. It is successfully able to eliminate the incidence of inner condensation in pitched roofs due its air permeability and low vapour resistance. If you’re looking for the most cost effective solution to controlling condensation in a pitched roof, then look no further than the Roofshield breathable membrane. This is currently the only product on the market that can offer you all of the following: Air permeability Doesn’t need an additional vapour control layer Hydrophobically treated Low vapour resistance Supplied in rolls of 1 m x 50 m UV resistance Water resistance

You can either suck air from the loft and blow out of room vents, or suck in through room vents and blow out of wet rooms. I prefer the later but either will work. PIV may be easier to install. But either way I would want it humidity controlled to limit ventilation when possible. So fan humidity controlled and room vents the same. This way you only really ventilate where it's needed. So if PIV, find one with humidity control of fan speed Or dMEV fans in wetrooms only, something like Greenwood CV2 or CV3.

No it's an MVHR combined inlet and outlet

Why PIR, it could shrink, giving you breaks in the insulation. I take it's going between the 125mm studs? I would increase depth of stud and do mineral wool, wood fibre or even cellulose pumped in. If it's not structural why not use 600mm centres this will lead to fewer thermal bridges.

That's because everyone is brain washed by plumbers wanting to install 30kW+ boilers. Doesn't that far out. MCS start doing 2 or 3 ach which soon racks up the heat loss. Your calculations assumes the room above is also heated, which is fine if it is. And should be with ASHP anyway.

Effectively completely ignore the GSE instructions, they are not applicable to a sarking board roof. Attach the trays direct to the sarking, through the membrane

You have self balanced actuators, maybe it was just going through a learning period, some can take quite awhile. With SQ610, you have a setting that optimises control to the Salus self balancing valves. Go on to Google and search for the full instructions for the SQ610, not the quick guide that comes with the thermostat.

Buy the correct aluminium capping pre made. You will not get a sharp bend without a proper bender, and depending on grade of aluminium it may crack.

So do you have an issue?

Not sure I would ever hand that over to someone - what you actually want and they will assume is ok for will be very different. Do your own leg work. Get the right architect they will handle that for you. Turnkey and to first fix are very different. Turnkey you give them an empty site, you then move your furniture in. First fix is generally before any plasterboard has been installed. Lots of work to do after 1st fix