JohnMo

Who knows, still not really relevant to heat pumps currently being installed or installed in the last decade or more, they all had/have 4 way valves. If someone has a historic ASHP, that doesn't do refrigerant defrosts, good luck to them.

Article from 2012 discusses how a 4 way valve is used on a heat pump https://www.danfoss.com/en/service-and-support/case-stories/dcs/components-for-heat-pumps-part-5-four-way-reversing-valves/ Carrier started using them in production models in the 1970/80s. So for all purposes of this discussion, 4 way valves have been about for ever.

To support the above. An a2w heat pump is really a2a with a water heat exchanger added instead of a house internal fan coil. Cooling is a pretty simple concept for the actual heat pump, heating is quite complex, as you need to accommodate defrosting, hence the addition of the 4 way valve. ALL heating ASHP can do cooling, as they all have a functioning 4 way valve. Many manufacturers deploy ASHP without cooling controls or add the controls as an option extra. Interesting fact, my Hiaer heat pump comes with cooling out the box, but add a smart optimization system, cooling becomes no longer available - go figure.

Last year I automated mine via flow temp set point and stop start hysterisis, and ran circulation pump 24/7. Ran on a pure demand cycle. New heat pump won't be run that way, as 8 don't have the freedom change some of the parameters, now will have a room sensor doing the automation, so I get cooling whenever I need it, heat pump run on fixed flow temperature

We are mostly oak on top of concrete, and the effect of cooling is pretty good. Good analogy We had two similar days one pre cooling and the next with cooling. Cooling knocked around 3 degs off absolute max temperature, but more importantly, once solar gain stopped, house recovered to more normal temperature way quicker. I look at cooling as a freeby of having a heat pump installed. We get what we want, at zero install cost, is it Aircon - no, do you need Aircon maybe not. Having lived with Aircon for a few years (overseas), not sure I want the endless air blast either. UFH heat and cool, is an easy to live with option. In absolute terms the cooling isn't designed, we accept what it provides in comfort a bonus. Our cooling will be stitched on next week and stay on until around October.

Not really a shifting argument, different solutions to the same issue. The larger fan coils at a flow temp of 17 are not quite as good as Aircon, but in nearly every case more than adequate. Way less faff to install than flowing at 7 degs, better CoP also. Give them two options, all singing all dancing, plus a few of grand in install costs covering, additional insulation, condensation drains, electronic mixing valves etc, worse CoP, and more complex commissioning or a comfortable night's sleep in hot weather and a super simple install. 95% of installs would never ask for cooling anyway.

It really isn't that difficult - UFH flow at around 17 degs, job done. It's above dew point for the piping, and therefore the floor, no matter what the build up. It even works at 300mm centres. Fan coils just over size them, run at the same flow temperature as the UFH for heating and cooling. No additional pipe lagging needed for cooling and no condensation drains. A good compromise.

The floor becomes the cold area, so the room and more importantly you radiate heat to the floor. The water picks up the heat gain from the floor.

You can have it working exactly the same A2A with fan coils. Just flow at 6 degs and can be as cold as you want.

Not really correct. UFH works on radiation (around 80-90% and 10-20% by convection) not convection alone. Our 6m high ceiling is almost the same temperature as the wall thermostat reads. No cosy feet really either, the floor is actually cooler than your body, typically only a little warmer than the room. Cooling works in just the same manner, by radiation, instead of heating it basically sucks the heat from you. So although room temps may drop by a couple of degrees the house feels way cooler and more comfortable.

Someone the other day had a radiator system that currently runs at 45 degs, he was getting quotes circa £13500 before grant for a heat pump and some install works - utter bonkers. But generally most R290 heat pump seems to modulate well. But not all will do cooling if you need that. Example, current Grant heat pumps physically will do cooling BUT their controller does not allow this happen. Most installers are clueless about cooling, so be prepared for plenty of BS.

Not sure a single night will give you an exact heat loss rate, as any day time gains will still be there. Suspect your real heat loss is somewhere between the two figures. Plus the heat loss spreadsheet uses min BR U values not your real ones. But basically your ASHP model choice will depend on actually output at you min outside temp. I would understand size not over size.

I have just moved the previous house heat pump to heat a hot tub, installed a brand new heat pump for heating and cooling the house for around £2500. Pretty similar to OP scope, new heat pump, he needs around 7kW so a Hiaer 7kW would be just fine, it's a little more expensive than the 4kW that I am using, so add another £5-600. Use DHW as it is via immersion.

Slightly smaller planet than that, most self builders aren't really self builders, they get a builder to build a house, the builder dies what he normally does. Detail is someone else's problem.

My manifold is in the centre of the house cylinder at one end, just have 15mm pipe between the two. But that is just a sad reflection of the low skill levels in the UK and zero focus on professional development.

Series - long pipe from cylinder to last service off take, intermediate user tees off the long pipe. Generally all tees and other joints hidden in the building fabric. Radial, pipe from cylinder to manifold (with or without isolation valves) pipes go direct from manifold to user point. No hidden joints in the building fabric. A hybrid of this, is a radial system to each wet room and then in room go series.

The software company is a different company, so that's ok for now. BUT if we want all the bells and whistles you have to pay monthly. The hardware unless bought over there goes the warranty. But battery inverter do not need cloud based services unless you need remote access and monitoring. It can all be controlled locally. Several alternative controllers out there if you need them. Big BUT, they won't be the last, tech startups come and go

Why would you bother with the grant? Just paid £2100 including vat for a heat pump, you just need some isolation valves, anti freeze valves and some piping. Do an easy install, leave DHW as it is heated via immersion, and let heat pump doing heating. I have a Haier heat pump, no issues.

They do. Min size should be, based on number of beds would be 270L. Section 3.5, would say 175 and 210L are way too small for a 5 bed. https://mcscertified.com/wp-content/uploads/2025/02/MIS-3005-D-2025-V1.0.pdf

Not the best decision, but yours to make, as long as the size of cylinder complies with MCS regs - which it may not unless your in a 2 bed property - your worst case is short cycling doing DHW. Plate load as a minimum, ideal skip it and a suitable sized heat pump cylinder.

My comments 22mm main run for DHW, will take an utter age to get hot water out the tap. You really want a manifold system. Mine is DHW cylinder - 15mm to manifold central location, then from manifold 15mm run to each wet room and spur from there. No comment on price

Going to be less than efficient doing DHW, via a heat pump, as you will have higher flow temperature to get the same cylinder temperature. It also sounds a very small cylinder for the high usage of water you seem to have. There are only two of us and we have 210L and wouldn't want any smaller.

So is your existing cylinder a typical gas cylinder? Or a direct cylinder (just immersion)?

Where are you located - your profile dies show it? Your design case (outside temp) is something like to cover 99.7% of the time, so your -8 is very likely not going to be applied. Why, do you have a heat pump coil or are they adding an external plate heat exchanger?

Still no idea what you are doing - over thinking or a real design issue, is it 1 m² or 100m², ground floor, 1st floor, what is the steel doing?