Marvin

I didn't say I use weather compensation so auto stepped temperature targets.

Silicone it in using Dow 785 white - (allow 24 hours to dry whilst not fitted to sink and in the dry and warm)

Possibly: https://getplumb.co.uk/products/mcalpine-1-50-x-1-75-bsp-coupling?

Can someone clarify this for me please. ASHP involved: Cool Energy CE-iVT9 Set up: Buffer tank to radiators. 205L hot water tank. Carel PGD1000F00. Question: Relating to heating only (for clarity) : Does the temperature of the water heated by the ASHP change as the temperature set point of the buffer tank changes (example A) or does the output temperature of the ASHP stay the same but only heat the buffer tank up to the set point (example B)? Example A: ASHP heats water to 5 degrees above the Buffer tank set point and heats the Buffer tank until it reaches the set point. Example B: ASHP heats water to 50 degrees and heats the Buffer tank until it reaches the set point.

True @joth I forget we have PV and radiators (not a thick concrete slab for massing) which makes it a different calculation! I think that, just as with EPC's, there is no one-design fits all and that specific property equals specific design.

Most efficient way to run an ASHP is low and slow: low temperature, which will mean longer to heat up. For a simple understanding: the less difference between the out side air temperature and the temperature of the heated water leaving the ASHP the more energy efficient the ASHP is running. We have ours running using weather compensation mode. At this point the outside temp is 4.6C and the ASHP is running at 40.1C. However, we are using all radiators with buffer tank and secondary pump with home temp ranging from 22 to 23 C.

I'm sorry I can't help. live in a bungalow

I used SWA. The energy can go both directions remember...

When I did our side extension flat roof connection to the eves side of the bungalow I used OSB vertically all the way up, in between the roof joists, sealed the gaps with mastic and then put plastic over the OSB and sealed the edges where necessary before insulating, to protect the void. When PIR insulating I foamed every gap that was between any timber and the PIR.

Always Terram down first in my book. Temporary surface on top is a discussion depending on the site size and use.

One expansion vessel for the primary water circuit which connects the ASHP to the coil in tank and heating system.

MVHR unit will trickle water when the outside temperature is lower than the inside temperature but doesn't need a tundish. It is meant to drip. Tundishes enable you to see that there is a fault because it is dripping. My MVHR has a waterless trap which runs through 22mm plastic to a waste pipe connection. The hot water to the tundish needs to be as the regulations show: max of two 15mm connected at the top. 22mm below copper all the way.

Easy one first: 3: https://www.bes.co.uk/push-fit-overflow-reducer-from-waste-32-x-215mm-11244/

Hi @Spinny Simple tests you can carry out: If the expansion tank is connected uninhibited to the hot water pipe I would turn the cold water supply to the tank off run a tap until there is no pressure in the hot. make sure no one uses the hot water for say an hour. then turn hot tap on. What is the result? If there is no pressure then the problem is related to the cold water. However if there is pressure it could mean there is a problem with the hot water OR the cold water.(some taps will allow water to pass from one to the other supply when pressures are greatly different even when off - perhaps I use too cheaper taps 😂) Turn the cold water supply to the house off this time. do the same to the cold water. If there is no pressure then the problem is related to the hot water. However if there is pressure it could mean there is a problem with the hot water OR the cold water. Good luck

Hi @Spinny Lots of alternatives here for you to consider... You said a lot when you wrote that the drips in the tundish were cold in my opinion. I would have questioned if the cold water pressure reducing valve (PRV) is working correctly. If you needed a water softener it suggests that the water is hard and this can cause limescale buildup. If the hot water is under a lot of pressure when first turned on but when left to run reduces in pressure and slowly increases when shut off again it suggests the PRV is letting a small amount of water pass through all the time. Sometimes water pressure can run out of the cold and into the hot when a tap is turned on so I think both having high pressure should be ignored at this point. What you need to do is have the softener installed for sure. It must have been planned for a reason... As for the expansion tank. If it is set at 3 bar, then anything below will not fill the expansion tank, anything above will start to fill the expansion tank. I hope this helps Good luck M