JohnMo

I would get a smart meter, you may need to press them for a 4G version. Believe they run on Vodafone, so check if you actually have a signal. A least with a smart meter you can get a selection of tariffs, no smart meter you are just on standard rate or E7.

That's ok but not really how it works. You house has a defined heat loss. The radiators are there as a heat transfer mechanism to replenish the heat lost. The boiler replenishes the radiator. So you start from room heat loss, you specify the radiator for the heat loss and means flow temp through the radiator. You add up all the rooms and that gives you the boiler size. But none of the above really matters, as either the boiler isn't pushing the heat outwards to the heating system, or the heating system cannot accept it due to something physically stopping it. Looking at the datasheet the output of the boiler is 3.5 to 35kW. So pretty good modulation. Flow required through system is well below my heat pump and your piping is well suitable to my flow rates. So unless there is a real issue with the boiler itself, you have the following possible issues Filter clogged A strainer in system is clogged (shouldn't be there if you have a filter) Gate valve added and boiler control is just confused as it doesn't make a difference when pump speed is modulated. Or an isolator valve not fully open. Or piping doesn't match your layout, plumber messed up with pipe routes.

Take some photos of the boiler and any piping especially any valves. Our last house was 3 storey sandstone house almost no insulation and drafty - it was 6 bedrooms etc, we had a 34kW and it never struggled even in the depths of winter in Scotland. From heat geek website if you have an older Victorian or pre-war building with little upgrading — say, single glazing and minimal loft insulation — you should expect 95–110 W/m² (of total floor area, not just ground floor). If the same property has upgraded to double glazing and some loft insulation, this drops to 65–85 W/m². Further upgrades such as cavity insulation can reduce it to 40–65 W/m². Pre-2006 builds or recent full renovations typically range from 30–50 W/m². So look at you total floor area and multiply by watts to get something close to your heat loss.

Don't actually think any MVHR unit needs them, they have in-built frost protection, mine slows the incoming air rate down a little, then when everything is ok goes back to normal speed. This has zero issues at -9. Enthalpy HE help with prolonged cold periods as your house doesn't dry out as much.

Can I ask a basic question, how big is the house and what is the calculated heat loss. For 36kW, it has to be pretty big, uninsulated and pretty drafty. Is this the case? Boiler are pretty simple in a lot respects. They are trying to heat water, the bigger the boiler the higher the flow of water needs to be to move that heat away. The boiler unless told otherwise runs flat out, throws as much heat as it can initially, then if it senses it can, it will modulate output down. The idea is it runs as long as it can. Your boiler will modulate power output and circulation pump speed to do this. Some boiler have a setting (bit like acceleration rate) where you can set the ramp rate, so how many degrees of heat are added per minute, this slows everything down and lets the system catch up. But the WB8000 doesn't have this. What does exist is I believe is Gradient Limitation (Temperature Blocking) The boiler itself has an internal gradient limitation control: It monitors how quickly the flow temperature rises. If the rise is too fast (above a programmed limit), the boiler will temporarily pause the burner for ~2 minutes until it’s safe to continue So you are possibly seeing this in your video. Your circulation pump is a PWM, so it will try to maintain system dT, to within defined limits. To do this on Rising dT boiler increases pump speed, slows it for reducing dT. Your system seems to be fighting this you have what is described as an open system, big pipes, big radiators etc. So unless a valve is closed, you have a blockage or you pump is failing (doubt that). Has the plumber installed something (gate valve or similar) to force a dT against the boilers wish and as such gagged the flow.

Are all your radiator lock shields closed too far, so little or no water flows through system? Are you certain you don't have a valve closed somewhere?

Not sure what you mean here? Disqualified from what?

Maybe for the house AND outbuildings. You can easily run both from a single heat pump.

Dust in the duct etc. I had a Dyson once lasted an hour sucking up building dust (motor failed). It's super fine and gets everywhere. A Dyson is small change compared to MVHR. Another dehumidifier?

A HiSense 4.4kW will come down to 1.8kW at 7 degs, so add a 50L volumiser, you will cycle about once per hour. £2100 delivered, plus you can claim the vat back on a new build. So a little over £1800, volumiser £100 to 150. A heat pump cylinder sized at 45L for each bedroom plus 45L, around £1200. MCS as @Nickfromwales says, will want a standard design, so radiators in each room etc. And still charge an arm and leg. If you size you fan coils correctly your flow.temp will never exceed 35 degs for heating, so you should get a scop of 4.5 or better.

Yep, our longest over hang is about 4m. Basically fixed to two wall plates. Whole roof was engineered by posi supplier and approved by structural engineer. Each end of the house has a 6" steel pole anchored to a big block of concrete, as additional hold down

Trouble with mixers is they mix, so quite a lot of return water goes around the loops again, so inlet water flow rate can be low. So low flow rates a 3kW heater, it's possibly boiling the water.

2kW doesn't sound a lot, but that's 48kWh a day at your design day. So would be pulling the cylinder temp down pretty quickly. Then you would be getting a rubbish CoP most the time. Not sure having the heating taken off the top would be that wise, as your DHW would always be cold. Think if you are going thermal store I would go proper thermal store. Have store as a pressure vessel, charge direct from ASHP, so no coils so heat transfer is 100% efficient. So if you store at 50 the heat pump only has to 50 degs flow. Take CH direct from store mid way up and return to bottom. Then have DHW via plate heat exchanger. Size at about 3-400L.

That shouldn't be the issue

What does your piping look like from ASHP to UFH manifold? Length and pipe dia. How long is the plastic pipe leading to the Wilo pump? The isolation valve on your Wilo pump looks to be a reduced bore, which will not help things.

So what is the difference between this and various emulsion paints, say a kitchen or bathroom which is more water resistant?

Brink do a system based around a normal MVHR unit. Basically they dump the supply air in the hall, similar to PIV supply only system. You do need to duct and extract from wet rooms. And depending on room layout you may need internal fans or if routing allows duct to some dry rooms. I read about it first on Passivhaus website. But search for cascade ventilation or cascade ventilation with heat recovery. You main thing you need to do is visualise where and how air moves about the house to make sure all areas are covered.

Our 12 degs roof is covered in the stuff, some off cuts have been sat outside for 5 years now. Not covered allowed to get wet. It's still in pretty good condition, considering.

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Most places that do ventilation. https://www.paulheatrecovery.co.uk/product/filter-cone-125/ They help protect the ducting, the main return filter is there to protect the heat exchanger. But sounds like you will be a while before you are switching on. Don't be tempted to switch the MVHR on early, it maybe one step forward several backwards.

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 losing 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.