Michael_S

You are doing well to even find out how much most heat pumps on the market modulate, most manufacturers seem to keep this info very close to their chests.

The only advantage for me is that should you get that long power cut or a system failure you don't have to drain the HP to protect it. Downside of course is the reduced efficiency in heat transfer. We are running a second circ pump (due to undersized pipes) so it is only the prolonged power cut that might cause us a problem whereas adding gylcol would definitely result in a reduced heat transfer rate problem.

Could it relate to over voltage in the mains? We have a wifi enabled RCBO on our HP so can see real time the voltage, current, watts, leakage, cable temp etc.

Our series two has a built in immersion in the heat pump unit in a very small horizontal 'cylinder' which we have both disabled via dip switches and physically disconnected. There is a downside that this is part of the de-icing mechanism and we did have some issues when there was a 3 day hoar frost earlier in the year. WE also run a secondary circulating pump due to undersized internal plumbing but have to be careful it does not generate too much flow through the HP during start up as the heat pump sees this as the flow sensor being stuck open and errors out.

IN terms of aesthetics (wherever the HP is sited) - does anyone have any experience of using this type of screen to improve the visual appearance? https://www.amazon.co.uk/Conditioner-Aluminum-Ywanwj-beautifies-accessories/dp/B0F1V45YY4?th=1

Agree with you re efficiency but it is more abut sleep comfort - I guess it doesn't take long to get used to warner nights as we do it every summer.

With the gas it is tempting to do a overnight setback and of course there is turning down to min heat during holidays and this is when the furthest rads take a while to warm up and then warm the room back up. That being an issue with the gas it is likely to be even more so with a heat pump. the issue not being total power output of the heat pump but how quickly that energy can be transferred to the the rads (whatever their size) due to the pipework constraint. Obviously with an HP I wouldn't use such a big set back.

How thick is your 'backbone/main loop' though - ours is rather long due to the house having bene extended and the whole upstairs is 15mm. The online tools suggest the most the upstairs rads could output is about 3.85kw at any sort of reasonable flow rate and that rate would only be achievable if you only take the total length of the circuit and ignore the corners and fittings.... On the other hand it does work with our gas weather comp boiler running at 55C at min outside temp but it takes a long time to warm up after a cool down in the furthest room, fortunately the gas boiler can modulate right down and keep the flow going rather than on/off..

Sorry, meant flow temp not flow rate - eg I know a conventional rad rated 2kw at 50C deltaT will output about 41% of that at 25C deltaT (45C Flow temp). How about a 2kw rated fan coil - us it the same?

For reference, I am currently replacing some rads in preparation for a heat pump, given restrictions in my circulating pipes it seems like I can't realistically go below a 45C flow rate for the coldest day so am sizing my rads accordingly so have not had to go up to triple panel or change sizes, rather just going from type 10/11/21 to 20/21/22. However the thought that if I were to use fan coils I could also use the unit for cooling is obviously quite tempting so there are 3 or 4 west facing rooms that get the hottest where fantails (if they have the right output and are not too ugly nor noisy) would be a tempting option.

Thanks for replying, beauty is in the eye of the beholder I guess, to me they look like the cheap rads/night store heaters you get in a bedsit so negative connotations. I found your other thread on fan coils and one question seemed to be about condensation if used for cooling. I was thinking that the forced air flow would tend to evaporate any attempt at condensation and so the problem would remain with the pipes not the rad itself? Finally it seems a bit harder to work out what the equivalent output in watts is for a fan coil for a given flow rate. It often seems hard to fathom out what deltaT they are using for their stated output and what adjustment factor should be used for a lower flow rate? Final finally, many of the units suggest that they only activate the fan if the flow rate is 35C or over - not much use for a heat pump running weather comp nor for cooling!

Thanks, new unit seems to be about 3k. Would we get enough back on the old one to cover the cost of getting someone to do the work? Either way seems a lot for a minor convenience gain.

So we have a set of doors, at one end we have a single opening door. This hinges on one end of the frame and latches to the bifold section that is made up of 4 pieces on a slide track fixed at the other end. It would be a big win for us if the single opening door could be at the other end of window, ie everything flipped. My guess is that the only way to do this would be a completely new set of doors but I would love to be told otherwise....

Fancoils seemed to be a lot more expensive and of course need a power supply nearby - and to me tend to look ugly... We decided a 45 flow temp was a sensible trade off between efficiency and rad size. I use da standard table of deltaT reduction factors, probably should have looked for rad brand specific ones but decided it was probably good enough. I have one rad that is claiming an improbably high BTU at deltaT 50 so I guess we will see.

Thanks James Interesting wording. It would appear that if you had previously heated your home with a heat pump but not had a grant, were the heat pump to break, if it were removed and you heated with resistance electric then you would be eligible.