JohnMo

Big Red heat pumps used to do them. Spoke to Harlequin about them, but the heating coil wasn't that big and you lost quite a bit of cylinder volume with that and the DHW coil. So moved to UVC, which is a good solution, either big coil, or existing cylinder with PHE and pump.

So will get full low sun mid afternoon onwards. Plan for overheating. We have 36m2 of glass in out living room, which is southwest facing. It can get very hot if you are not careful. Not to bad in the winter, with triple glazed 0.6 U value, but the lounge looses as much heat as the rest of the house.

Why not just get a quote from MBC, instead of going around different groups, what ever answer you get, will not be the same answer given for your design.

Choose your battles, foundations have time scales. Dig, building control inspection, fill with concrete. Leave it too long or take too long, they fill with water or the sides collapse. Access starts to become an issue, once you start, depending on the site layout.

Because they have an excellent turndown ratio. By that I mean minimum output which is something like 1.8kW, compared to must which have nearer 6kW for the same boiler rated max output. This helps minimise short cycling which can use lots of gas. Other good things you get with a good boiler are two flow temps one for heating a cylinder and the other for central heating. With gas boilers the lower the return temperature back to boiler the higher the efficiency. Irrespective of heat source chosen I would design the heating system and the hot water the same (unless you want a combi boiler). Heating system design for low flow temps and hot water storage design around a heat pump cylinder with storage temperature of 50 and below. If you go combi, get one that will take preheated water (Atag, Ideal, Intergas to name a few). And read the papers below - been there and it works well. Combi-SuperFlow-White-Paper-v1-2-4.pdfCanetis-SuperFlow-Product-Sheet-WE-050318.pdf

Ambient temperature during the heating season is very different between the two countries. So therefore the SCoP for ASHP during the heating season is very different. Building and population density are also very different. You are comparing apples to oranges.

https://mixergy.co.uk/news-and-insights/plate-heat-exchanger-vs-coil-the-great-debate/ Interesting read, but does generalise with respect coils, making the assumption that all coils are just a single coil. Most coils are now multiple coils run in parallel, so you could have 4 to 6 separate coils fed from a manifold to make up the coil stack. It assumes the coil starts a fair way up the cylinder. My nothing special off the shelf cylinder, the coil starts as low down as practical, being just above the immersion. Not as low as the mixergy but not 20% higher as indicated in the text. I do believe the extra heat transfer efficiency. But you have an extra pump in the system also. The bit I find worrying for the real world is this - 4 hours to reheat the cylinder. https://mixergy.co.uk/news-and-insights/real-world-performance-of-mixergy-and-heat-pumps/search

Decent digger driver, job done. Worth their weight in gold. Digger and normal laser.

Noticed a few fan motors on eBay, may be worth asking for the part number...

In fact they would always trump any building standards requirements. Except a noise requirement and anyone with half a brain can work through MCS-020 noise flow sheet.

As above no. If you specify a suitably size UVC and water is sitting for weeks. If the contents of the cylinder don't get used, then there maybe a case to heat once a week to 60 Deg or if you someone in the house with a suppressed immune system. There are two of us in the house and we have a 210L cylinder it gets heated to 50 usually twice a day. If mains water, or borehole with suitable treatment system and in a closed system where air, debris etc. cannot get into the system, no contamination can occur.

But MCS standard done by anyone other MCS is the equivalent. After all a MCS Main Contractor can dish out just about the whole scope to any third party, sub contracted by an MCS main contractor.

Unvented cylinder, heated by ASHP to 47 to 50 degs.

Really depends on what the supplier pays you per kWh export. If you have a smart meter you could get 15p if you don't or live in a area where they don't function it's 4p. So even then it's best to self consume as much as possible.

We started with a combi boiler, driving UFH, thought nice, easy, cost effective. But getting a big gas boiler to work well in a low energy house isn't easy. They just short cycle, using way more gas than they should. Eventually got it working well. But swopped it last year for an ASHP, all self funded. Doing it again, ASHP every time, 3m2 coil UVC for hot water. House heated as a single zone. Three ways to heat Fan coils not the cheapest option, but good for cooling and heating Big radiators run on weather compensation or UFH on the ground floor and any upstairs bathrooms. Add provision for electric panel heaters in bedrooms, just in case you need them. If doing UFH do a 100mm thick screed and charge on a cheap tariff the same as a storage heater, or thin screed and run on weather compensation. MCS grant scheme should be the cheapest, but just seems a rip off get quick scheme for installers. From everything I've seen Panasonic ASHP seems very good, something like a 200L cylinder, and heat emitters is all you need. £4-5k all in, plus install, and there is nothing complicated. Insulation and ventilation will have an impact on heat source sizing. Best advice I have seen. We have done many kitchens in many houses, back in 1999 we spent 25k on a kitchen, latest one in 2022 was about £7k and way nicer.

Once you get below 15W/m2 there basically nearly no difference in flow temp between different centres. Something like 2 or 3 degs between 300 and 100mm centres. As mentioned the only difference is response time. With thick screed the response time is many hours per 0.1 Deg anyway. So I just did 300mm centres. Easy to install, 8 loops over a 195m2, batch charge overnight on E7 at 35 deg flow temp.

Possibly a good solution. Would keep your options open to makes and models, while R290 may give high temps nothing wrong with R32. I laid £1300 and some else just got a Daikin for £1200. Same Vaillant is circa £3500.

One issue with combi preheat is the cold slug of water between TS and combi, the combi always fire up every time a tap is opened. So you need a solar diverter valve close to the TS outlet. Take a look here also. https://originaltwist.com/2016/06/23/eco-heating-system-for-heat-pumps/

Generally I think you have to much time contemplating and ended up with a complex solution. Way to complex. Read some of my threads I have been there done most of it. Sounds like you have most of it already. With what you have I would do the following. Sell the thermal store and get an UVC. Combi, blank off the DHW side. Use the boiler as an UVC heater on its own or in combination with the ASHP, in hybrid mode. Use the ASHP to drive your heating. Don't bother with the back boiler.

I'm in the same boat as you. Equivalent really means nothing. Don't see why me following all the MCS guidelines isn't the equivalent of a MCS person doing it. My noise is easy, main road 150m away nearest house 400m away. The heat pump can do all heating and hot water without issue, even if I used MCS calculation and ignored MVHR.

Nothing to do with your air test results. It's how much your ventilation is moving in and out of the house, the figure is multiplied by the MVHR efficiency. For a leaky house you would add like 5 or 10% of your leak test figure to the air changes per hour. Your lowest mean is for the coldest day. The monthly average in this case is meaningless. You really need the historical average not this year's data also

If that's the case there looks to be something not right with the heat loss calculation - rubbish in - rubbish out

Air changes per hour will be ventilation rate, so if MVHR with 0.3 or 0.5 MVHR hourly volume, did you add that figure, not sure where it came from, as it doesn't appear on my copy? Not sure you your mean temperature make much sense, your coldest day is 5.3 degs, we had -9 for 4 days straight this year and last year.

That is what I use, but the model with a timer. Set it to come on morning and evening and set the return temperature to about 35. Only runs for a couple of minutes time. There are two sizes, you just have to watch the head required, the small one is a very low head output.

My heat demand is around 3.5kW at -7. The heat output is 6kW at -7. On that temperature day the heat runs for around 12 -14 hours. On an 8 degree day it runs for a few hours. If you installed an 8.5kW heat pump with a demand of 8kW, your heat pump would have to run at nearly full load 24/7 to cope. If you want to batch charge the floor oversized is ok, in fact it has to be oversized.