JohnMo

Hope it's better than decorating caulk, which shrinks after a couple of years and leaves gaps everywhere.

Would have thought so, but only up to a point, if you have big gaps everywhere, you may be fighting a loosing battle. Have you done a pre plasterboard air test? Then you know where you are and can discuss what is is achievable with them.

I use cone filters in each extract terminal, you would be shocked how much dust they stop getting in to the system.

Locate as shown, drill holes through wall from extension low down (piping level), and excavate area under manifold, connect UFH pipes, pressurise. Then no joints needed etc. cover manifold with some insulation to protect it from bangs and knocks. Is it worth the hassle and increased expense to install boiler stove, piping and additional heat dump etc?

If you located the manifold on bedroom 2 / utility wall, you could takes pipes in to utility and terminate them on the manifold? Are you using the wood stove/boiler just for cylinder heating or UFH as well? Could you locate the ASHP nearer the utility? It looks to be on the south side of the house, which isn't ideal. Should be located out of the sun really.

You only need tiny amounts of water for defrost about 40L is enough for most heat pumps (except huge ones). Your min output is 1.85kW, so multiply by 20, do you only 37L to protect from short cycling. You don't need a volumiser with 60L.

Every man and his dog on that video. Good video through.

Gee this thread has gone mad, gone from what looks like an over calculation of 9kW, to people suggesting 3 phase monster heat pumps.

Flow is king with heat pumps. Excluding the mixer for now. Your flow limit comes from the flow meters on the UFH manifold. The flow added together of each loop is basically the max flow rate you can get through the system. Open each loop another 0.5 l/min, that will add 5l/min flow. To increase flow turn the black part of the flow meter on top manifold anti clockwise. If flow doesn't increase look at the mixer pump speed settings and increase the speed. Next - a later job. Your mixer isn't needed, it's just causing a bottle necks and unnecessary mixing. Plus it doesn't allow you to run weather compensation very well. You also need to run a higher flow temperature to compensate for the mixer valve. So get a worse cop. Two pump running cost you more money. I would be installing a single 5 or 6m head pump that does UFH and your DHW heating. Delete the mixer and pump.

We did something similar in our last house. If you want to keep the hand pump and make it electric. You basically need to take out the piston affair, from the hand pump so the pump doesn't pump. The pump then becomes an empty pipe. In the well, drop a submersible pump on a rope into the well water, pump size will depend on how many metres it needs to lift the water and flow rate needed. The outlet of the electric pump needs to be installed into the the pipe that leads to the hand pump. The original pipe that came from the well, to the hand pump should only have a single feed from the electric pump now, so will need to cut the original pipe or hose. So you need access to well and pipe that leads to hand pump. If have to make access not a small job. Run a hose.

Should hope so, they need to give you some for £5k for their smallest heat pump. Plus you have to pay extra for cooling! Mitsubishi is the most comprehensive, I've seen and I've seen a lot.

Don't rush to get running, especially while your still working on house, it will drag in all the dust etc - you don't want that.

You don't need volume in the cylinder circuit. Think it's because the water to water heat transfer is so good, compared to water to air on a typical heating system. But you calculate volume in the heating circuit to get away from any likelihood of short cycling, basic calculation, is you need at min modulation, min modulation kW multiplied by 20, assuming no tvrs or manifold actuators (any circuits with either are excluded from the volume in the calculation). That should be your minimum system volume, but more is better. The volume number in the manual is the volume needed to support defrost. If you need to add circuit volume stick in a volumiser, generally in the CH side only on the return piping.

The latest Viessmann ASHP do it slightly differently - on approach to defrost, they move an internal valve and charge a small buffer to about 50-60 degs and the whole defrost energy comes from that. Slightly more efficient to the normal.

Just the normal way, I just let the heat pump do its own thing - you don't need a buffer for defrost, you just need the minimum prescribed volume available, as detailed in the installer manual - you never did need a buffer, it just hang on from fixed duty heat pumps. Heat pump just moves the 4 port refrigerant valve to cooling mode, refrigerant does the defrost. Water circuit just provides the heat. It's only in defrost mode a couple of minutes. Attached from the other day when it was cold and defrosting. The attached is the temperature and heat flows. Green line is return temp (from heating system/volumiser), red line is flow temp, yellow is heat pump thermal output, blue area is electrical input. - no hat needed😀

Scottish building regs, just state a simple number, 0.5 ACH of whole house internal volume for MVHR (balanced inlet and outlet). Boost is above this rate. So no if buts or maybe, pretty simple, but leads to massive oversized ventilation on anything bigger than a shoe box. MVHR is also mandatory for any house that has an air test result of 3m³/m² @ 50Pa. The actual air test result is at 50Pa equal to gale force wind acting on all surfaces of the building - which can never happen, as there are always sheltered sides to a building. So actual air test result is factored down depending on your location etc. So in OP case 0.45 ACH at 50Pa is equivalent to 0.04 air infiltration, so pretty much meaningless in the calculation. Hence say that isn't the figure for air test result isn't the figure to add to spreadsheet.

Only thing I would add, the Jeremy spread sheet is designed for a high performance and pretty much airtight house. So if you are not that kind of house the calculation are pretty different and yes you do need to take into account natural ventilation as well as forced ventilation. So the build looks to be MBC which normally comes with a leakage rate below passivhaus levels. So at any point in the building life, the natural infiltration is next to nothing. So can be ignored to the gross heat loss pretty well sorted. But to do heat loss correctly you need to do the room by room approach Building regs drive you to 0.5 ACH throughput of the MVHR system. Passivhaus drive you to 0.3. Passivhaus is closer to where you need to be in winter so as not to over ventilate.

If you have just plastered that carries huge amounts of water. Plus if you don't have effective ventilation... Maybe get a dehumidifier until your ventilation is up and running (after decorating) Your vapour barrier is there to stop water vapour going into the structure and it rotting, why would you encourage water vapour to go there? NO. I would continue with the insulation and MVHR install.

We find exactly the same on a long thin (25m long) single storey. Open bedroom doors everywhere is the same temperature an hour later. Our last house 3 storey (built in 1830) bedrooms with doors open ended up same temperature as rest of house. We just never needed to have bedroom heating on.

But none of this detail is provided, so you are assuming, I was just asking a question. MBC build will need very little heat input (assuming it's not massive), so any heat added has very little place to go. So quite a bit of room temp equalisation will happen anyway, zones or no zones.

Its interesting when you read a Cool Energy ASHP datasheet, the broad range of outputs based on outside temp and how much things change. So pretty much the true reflection on how a heat pump operates. This is somewhat hidden by a lot of manufacturers which software gag the output. My heat pump max output varies by less than 0.5kW from + 20 outside to -15 at 30 Deg flow and it similar at 60 Deg flow. This is nothing to with physics, just software capping output as the outside air temp increases. But modulation is limited at 4.5kW (from 6kW nameplate) - pretty rubbish. It is the minimum modulation when you need it, that can kill overall efficiency. Stick in an over sized heat pump, you start to exaggerated any issues a correctly sized unit already has.

Whatever you do upstairs, do a floor buildup that eliminates any air gaps between heating pipes and finished floor. So people like @ProDave did a PUG mix, this acts like a screed so you get a solid heat emitter. You get lots on here that do different from that and then have huge issues. Are you likely to need cooling in the summer would be my question? My view why - would you zone?

If you have sized the heat source correctly, output at the sub zero temps should be at it close to full load. So it doesn't really matter how much it modulates at those temps. It really does matter at +7 and above degs outside. The heat pump naturally develops more heat output power, at minimum electrical input as outside temperature rises. So full load output of 10kW at -3 maybe closer to 12 to 14kW at 10 degs. So if you applied 4:1 to the 14kW it's a very different answer to 4:1 at 10kW (70% higher at temperature you want most modulation)

By people that want it to be true?

Its in the brochure, they state the 7 degs min out put for each model 4.4kW is 1.85kW 8kW is 2.1kW 10kW is 3.3kW etc They all do just about nameplate rating at -7 outside There is a huge technical book tha has all the details as well but I have deleted it https://solartradinguk.co.uk/wp-content/uploads/2025/01/Hi-Therma-Monobloc-brochure-2024-1.pdf