JohnMo

Just read the instructions, each one is slightly different, but an installer will set at 750mm unless asked to do differently.

Think if you read the manual it says auto adaption is for radiators, but if you have a very thin screed if should work ok. Once you hit a cold spell make sure the room temperature doesn't start to yo-yo up and down

It shouldn't, there is normally a diffuser to slow the cold water coming in and limit mixing. So the thermocline slowly moved up the cylinder as hot water is consumed. Once your thermocline gets close the the secondary returns port, plenty of mixing can occur and leave you just lots of cool water. Our cylinder temperature pocket is really close to the bottom of the cylinder, cylinder at 0730 was 48, temp gauge now says 21 after wife had a shower. I am going to heat until tomorrow morning to see how my shower is tonight.

Secondary circulation really needs a thermostat and timer and pipes well insulated. So thermostat stops pump when returning water is comfortable temp, when the water cools, pump starts - repeat. Timer so pump only runs when useful. No use loosing cylinder temperature, when no one in house or everyone is asleep.

Sounds like it's all been installed but not really commissioned. Why two heat pumps? Are you running through a buffer or low loss header or are the heat pumps connected directly to the UFH and radiators?

One the correct units the other not

or m3/h Lots of calculations on here https://www.omnicalculator.com/math/area-of-a-circle

Basically what ever they say as a throw away statement about pipe sizes, will only be true for a certain set of circumstances. You/designer still have design the piping system to manage total pressure drop, so you do not exceed the allowable system back pressure, and to ensure the circulation pump can meet the minimum flow rate requirement. Talking about exact pipe sizes, without a full design, is rubbish in, rubbish out and pretty meaningless.

Another thing to concider if you stay gas for hot water, is to install a heat pump cylinder anyway. The cylinder has a huge coil, boiler condensing for the whole heating period and lower flow temp settings, could save you 10 to 15% gas costs on its own.

Have tried to reduce cylinder set point, but resulted in max temperature at shower slightly lower than I want, so upped to 47/48. Currently still have two heating periods, the one in cheap rate takes 45 mins, the one in the day 35 mins. So next will try to have a single heating period instead of two. Even if I have to up the temperature slightly it will be cheaper than two heat sessions. Will report back in a few days.

Boiler or via a valve near the cylinder. Unvented cylinder is full of hot drinking grade water, so will not come that

Most R32 ASHP run to 60 without issue.

Or let them install a cylinder, which gets sold on later? Or let the heat pump try to heat the Sunamps, if it doesn't work well i.e. rubbish CoP, don't let it call for heat ever again. Tell installer what he wants to here, nothing more or less.

Reason it feels cool, is the shower mixer, always mixes in cold water, it's looking for the hot water to be about 10 degs hotter than the shower water comes out the head. So if you have 40 deg water you are having a 30 deg shower - cool shower. 48 is good for us, 46 is a not so good shower experience. Not really the economical way to do things. Reducing flow decreases floor output, so you compensating by increasing flow temp, leads to a decrease in CoP. The heat pump cycles, when it's below its minimum modulation, it's normal. The amount of cycling is likely to be outside temperature related. If your heat pumps runs around 10 minutes don't worry. The DHW out pipe is always hot, by not being insulated you are constantly transferring heat to the room, away from the cylinder.

The principal difference between the Chofu and Grant install. Chufu have a fully functional controller with built in thermostat and scheduler. Grant basically by-pass the design intent of this. Grant have modified the install to match a gas boiler, with two port valves, which have to be timed separately so DHW water cannot get into the heating system. There are several versions if the Chofu manual kicking about. This one has quite a few different schemes Chofu-Operating-Installation-Manual-R32.pdf

Self install is quite straightforward If UFH only ASHP to manifold, no mixer or pump. Set either a fix flow temp and control with a decent thermostat or set a WC curve. If you do it as one zone no buffer required, but system may benefit from a volumiser (long run times at low demand). You will need expansion vessel and relief, filling point, vent valves and a strainer. Biggest cost after heat pump is pipe, fittings, and insulation. If adding a DHW cylinder, three way diverter is added. I would look at a Grant heat pump, but install as Chofu intended. No other controls needed. Realistically you are looking at £3 to 3500, all the little bits add up. If you are adding a DHW cylinder an Ideal one are quite good price, good multiple coil comes with a 3 way valve. About £800 from City Plumbing.

It daft that cylinders don't have a series of temperature probes up the cylinder (say 4 equally spaced), so you can see how much hot water you have.

You also need to look at the route the pipes take, especially the hot one from the top of cylinder, this pipe can takeaway heat quite quickly, especially if not really well insulated or goes up from the cylinder. Ideally this pipe drops around 150mm minimum from the top of the cylinder as soon as possible, before going horizontal. This stops any thermosyphon effect.

It's in our summer house, which the wife uses for Reiki etc. so has to be quite. Had another make of dMEV fan in originally but it was too noisy.

No that how must trades seem to work these days from experience also. Their bosses have contracts with other companies that pay better, have call off penalties etc. You are just a fill in job, between better paying ones

Drill a hole down to insulation?

There have been a couple of similar threads recently, with links on how to do suspended floor insulation. Sorry can't be much more help. Take a scan through relevent sections of the forum.

Good catch with the mixer valves, the other thought I had was, to route the flow to the UFH first then use the return flow from the UFH to heat the pool. So in series instead of parallel. So your pool demand, acts a huge accumulator. You certainly get the best and steadiest output from the ASHP.

With UFH you need lots of insulation, aiming for a floor U value of 0.15 (150mm PUR, or 250mm of good mineral wool) or better or frankly don't waste your hard earned money installing and then for ever more, paying for heating.

In your letter from the council, they will list what inspection and what certificates are required. It is normal for a building control inspection, prior to plasterboarding, so they can inspect whatever they wish, prior to it being hidden for ever.