combined heat pump/UVC for DHW and UFH

[Tom]

I'm looking at the Dimplex

https://www.heatershop.co.uk/dimplex-edl270uk?gclid=Cj0KCQjwteOaBhDuARIsADBqRejTn69GZP1GFrPKsNMLBhwz7t4cxpwaRlVbRKjbGJsZ-zy5IW2NHDcaAre3EALw_wcB

and the Vaillant

https://www.theheatpumpwarehouse.co.uk/shop/heat-pumps/air-source-heat-pumps/vaillant-arostor-270-litre/

but it's not clear whether these can also run a closed UFH circuit too - I'm guessing not?

 

The Tesy looks like it can (https://www.modernheat.co.uk/product/2484/)

but doesn't seem available anywhere.

Has anyone any experience with running these for both DHW and UFH?

 

[PeterW]

None of the A2W combined ones do or really should be doing as they take warm air from inside the house and expel cold air outside and then heat the water. If they were doing space heating too then they would be creating some sort of closed loop perpetual heat engine … 

 

These are ok for certain instances and have their place, but not heating UFH

[Tom]

3 hours ago, PeterW said:

None of the A2W combined ones do or really should be doing

 

The Tesy one does, according to the marketing blurb. And they all seem to have ducted air supplies with schematics showing air taken from uheated spaces or outside.

[PeterW]

16 minutes ago, Tom said:

 

The Tesy one does, according to the marketing blurb. And they all seem to have ducted air supplies with schematics showing air taken from uheated spaces or outside.

Yes but a 1.2kW ASHP is the equivalent of just over 1 bar on an old electric fire ..!! Plus it then uses a direct immersion of the same power so it’s COP is around 1.8 which isn’t that great. 

[Tom]

Sure it's not the worlds biggest HP but it's better than an immersion alone.

Using the heat loss spreadsheet I've calculated my total daily heat loss power for January OAT: 5677W and for the minimum January OAT 6826W - energy input at 4224kWh and 5079kWh respectively. We'll have an approx ~12kW PV array on the roof. I've been considering using just an immersion for the DHW and a willis for the UFH, but thinking one of these combined units would make better use of my self-generated power and would have to import less.

[JohnMo]

So on a good day in mid winter your PV may put a very small proportion of your heating requirements on most days nothing.

 

So your January heating cost could be circa £1500 - minus your PV contribution - based on a Willis.  You could buy an 8kW Dream heat pump for £1400, just run the heating off it, good CoP easy install.  A CoP of 3 would £500 running cost, so midway through Feb its paid for itself.

[JoshHC]

Tom did you get anywhere with this? I'm wondering whether it's possible to use the heat exchanger in the Tesy to deliver some of the energy for a small UFH system, which then can be topped up with a boiler to get to operating temperature. This makes sense to be intuitively, but I don't know whether a boiler can be this dynamic, how would the system know to first take the base heat from the Test for example? 

[Tom]

Didn't pursue any further tbh, opted for the usual ASHP and UVC in the end, hopefully being fitted end of March - better late than never!