Don’t mind Terry, he’s just trying to add “value” 
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I would probably spec higher than that for output. For reference, our 8.5kW output Mitsubishi has taken in about 1.9kW (hence between 5-6kWh output probably) in the 12m to today’s date for heating only and it is specced pretty well for our heat losses.
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Yes, don’t want to under spec either.
Might have extension built to kitchen at some point.
Would want that as an added UFH loop.
I get where they are coming from work 8.5KW output.
They claim ASHP can handle down to 1.5HW and not cycle.
Although even when we had the loftroom and bootroom (can count them as an annexe) going full beans all year, it was still only 14000KWH / year.
That would still only equate to 4.8KW needed to achieve 20°C lift.
It’s all down to where in the country you are and the thermal efficiency of your home.
Those figures don’t even include the water heating being a buffer, so you actually need slightly less.
Of course if someone moved in and wanted every room on, all the time at 25°C, you might get to needing 8.5KW!!
After talking it through with them;
the bigger concern is how to zone the solution they have come up with…
They are wanting to fit one Madoka thermostat centrally.
So far they have not answered how this will effectively replace the 6 Polypipe zoned thermostats and the independent loftroom wireless controller we currently have and allow the flexibility we require.
They are working on it though🙂
Next step is engineer visit to suss more and see how zones can be kept to a minimum - can cause cycling.
Looking at mid to late Jan install.
Good to do in winter as it’s hard to evaluate UFH balancing etc in summer…
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A little update;
An engineer visited and we went through our typical usage of the main house and annexe.
He was confident the UFH zones could be balanced at the manifold to give the upstairs Vs downstairs temps we want - instead of switching each room on and off by its thermostat.
I’m quite happy fiddling with the flow rates to the zones to fine tune if required so no issue there.
The UFH water temperature can be much lower than boiler system, but run for longer - ideal for ASHPs.
Will give more even temps throughout the day.
Using the Cosy tariffs that have 3 periods a day at 51% cheaper electricity they said one will save £300 - against what I’m not sure.
Against non Cosy maybe?
That’s not a good way to run heat pump though.
I ran my own simulation spreadsheet based on our current usage and got £298 saving.
Assumes ASHP is around 330% more efficient (SCoP of 3.3).
But the saving isn’t the whole point.
Getting new gear, a water cylinder repositioned where we want it and the boiler out of the utility room is in there too.
So fast forward and we had it installed.
A Daikin 8kW unit, not the over sized 9 or 11kW beast that they started out assuming.
The MCS (guidelines or is it chapter and verse for Boiler Upgrade Scheme installer calcs are ridiculously over estimating property heatloss!
All went smoothly with the install.
The installers set up is not even close to how I’ve got it setup now!
We would not have saved anything with it like the installers left it. It would have cost more!
It would have been bouncing off and on at the whim of the thermostat.
Too hot sometimes, probably a bit lower than we’d like at others. Just like the boiler!
Switched away from thermostat in the hall control to Leaving Water Temperature / Weather Dependancy Curve control.
The installers made a stab at Weather Dependancy Curve control but it was based on the survey heat loss etc and they are never that accurate.
That reckoned we’d need 50C water at -3C.
Way too hot.
We actually need 32C water at that.
Warmer temps see the heating water at 30, 28, 26 etc.
So much more efficient. Can easily see COP of 4/5 and even 6v on a 10C outside temp day.
Slow and steady is the name the of the game
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After 1.5 months of tweaking it’s really comfortable.
Even temperature day and night throughout the whole house.
All the underfloor heating loops, towel rads just slightly warm too touch etc. Just a really nice experience.
The Domestic Hot Water was set on reheat / fast heat! Keeps it’s at 50C as soon as it drops below 40.
Changed that to 45C once a day when it’s warmest on the slower ECO setting.
DHW COP was 2 and worse when cold outside! Now get 3/4 easily.
We run a hotter legionella cycle, but there’s apparently never been a reported case of the bacterial disease from domestic properties in the UK , so far…
Month of Feb was still dialling in, and it still returned a bill of £30 less than the gas heating round have been.
Future months will be better.
Our install was cheap as no rads needed changing.
Underfloor heating is ideal for heat pumps…
So this may not be everyone’s experience.
So many ney sayers around about heat pumps.
Very common tech in Nordic countries.
Watch Heat Geeks YouTube content if you are curious.
They’ve got some really efficient rad only installs and in older less will insulated properties too.
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