JohnMo

You could, but not very good for DHW. It only outputs a single flow temp, DHW flow and CH flow temp is done at same flow temp. It really pool pump with a couple of additional features, but not much. Even the inverter one is a single flow temp for DHW and CH, it just modulates it's load not the temperature.

Sounds like setting issues .ore than anything else. Time to get the manual out and read a few times until it makes sense. Do you use most your hot water each day - if so you don't need to disinfect. Heat Geek have a good write up the subject, with the risk etc. Heating you cylinder from 48 to 60 will take over an hour with a 3kW immersion. If you want to hold that temp for 30 mins you need to set to 1.5hrs run time. But if the immersion isn't heating there an issue, it's tripped on over temperature and needs to be reset or it's thermostat is set too low so it's not starting.

Single flow temp for DHW and heating, fixed duty, so you will need a buffer most likely.

I know a bunch of fittings came with the pump, including nrv. But cannot recall exactly what. I would wait until you get the pump and go from there. They change design all the time,

My UFH has never reached 45 degrees, for UFH - it never will. I just started mine as low a temp as I could, ran for a couple days, increased slowly to about 35 and stopped there.

Output chart for the various sizes and different flow temperatures

This mine installed, used 1/2 to 15mm compression fittings. No 1-1/4 ports?

A bit bonkers really, good job I only paid a fraction of that. With high water temp it will chuck out 6kW, something a through wall would never do.

1200mm wide

Found 2 pipe version one online at £901 incl vat.

Bottom intake has removable, and cleanable filters.

They do two versions of the hybrid, refrigerant split and monobloc. The monobloc works with another manufacturer gas boiler. And it just tees in, from what I remember. Would think it would work on its own, a little bit of fudging about. Have a good read of the manual and make sure you are buying the correct model.

When I made some mods to my heating system and I added a buffer. Pretty easy to do. I used a 50L cylinder across the supply and return, so no additional pumps required. Your heat doesn't modulate, so needs some provision to dump loads to get a decent run time (about 10 mins).

My problem is the water comes in to summer house, at the other side of the building to the heater. So have to some how, get the pipes around the room without being an eye sore.

So garden room UFH, although just about works, really isn't much use at heat pump temperatures. So a bit of research later, have purchased a fan coil unit. A Myson iVector MK2. Bargain from eBay, about a 1/3 the normal price. It is a 4 pipe fan coil, so has two heat exchanges, one for heating and one for cooling, I will pipe both heat exchanges to a single pipe in a parallel. This should increase heat transfer area and hopefully be able to run slightly cooler. Fan coils come with a temperature sensor, and the normal set point is 32 degrees for the fan to start. So the water has to be above 32 degs to get the heater running. But the Myson one has an adjustable set point, so should simplify setup. So far have mounted it on the wall. Intend to use the UFH manifold to feed the fan coil, with the Salus actuators to manage a 7 deg dT. Heater on wall, with cover off and on

This thread is now 1001 posts long - bonkers. Length is all the words strung together possibly longer than your pipe length!

Top floor flat, downward heat loss should be arrested by the flat below. That sounds like a throw away statement. Ignore for now, although it says that on the drawing. What are your floor coverings?

Lots of recent threads on the same subject so have a read in the UFH section. Common theme is expensive to run, you need insulation etc. don't trust someone trying to sell you something

Fan coils may drive a buffer as they only hold a litre of water. Plus depending on which fan coil they may have a set or adjustable fan start thermostat, so as you heat pump cycles so will the fan coil fan on and off. So steady flow temps may be an advantage.

You can do either way. I would wind them all a couple of degs hotter than you need for now. Leave the UFH on for 24hrs and see what happens. Just do a set flow temp for now say 35. If the temperature starts to drop after 12 hrs add a couple of degrees to the flow temperature.

No issue with auto balancing actuators with heat pump. But does look like the UFH pipes have very little insulation below. UFH is very slow by nature, mine can run for a very long time to make any difference. I would dump the zones and operate as a single zone, run very long (all day) at low temps. Try to switch on and off at low flow temperature just doesn't work. How do you operate?

Are you certain of those flow rates, they all sound very low. But if you have a large dT that could be issue. If you add an additional pump, add it to the return leg on a fixed duty, so it doesn't interfer with original pump modulation.

You size heat pumps based on heat demand, those that say you size based on your house size, are not people to listen too, for any sort of advice. You need to calculate heat loss first. You need to find out your heat pump minimum output. You then size based on the min modulation output and system minimum capacity and heating requirements. The min capacity is the smallest zone capacity. Would help if you share as much information as you can about heating system, ASHP and house.

There is a min flow switch, if you don't meet min flow it trips the unit. The dT is managed by the heat pump it modulates the circulation pump so it's always at target. As dT reduces the heat pump add more temperature to also manage. Work best in a fully open system, otherwise you need to start adding buffers and possibly reducing efficiency.

Does the Chofu unit have a double set point? Could you just enable that via a smart relay? Homely doesn't want you having multi zones. It basically a WC system, with some "smart" features. You cannot install Homely without being an approved installer. It is approved to be installed on the Grant unit, so assume it just connects to the modbus.