Hybrid ASHP & gas boiler

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 Pedro50 14 Jan 2022

The council have just offered the above system worth £9,500 for free. Any views or experience? It claims the gas boiler will take over when the external temperature drops to 2C. It doesn't mention whether larger radiators are required or included. It does sound tempting

 summo 14 Jan 2022
In reply to Pedro50:

Sounds like you are paying for two systems when one will suffice. Or not paying in this case.

Post edited at 14:26
OP Pedro50 14 Jan 2022
In reply to Pedro50:

Update: I rang them and am not eligible because I have an EPC rating of C, it's only available to D or worse. This was not stated on the offer leaflet. Now disappointed.

 Ridge 14 Jan 2022
In reply to Pedro50:

I can't imagine the ASHP bit being much anyway use in a house with a D EPC rating.

OP Pedro50 14 Jan 2022
In reply to Ridge:

Agreed, better to spend some of the grant on insulation.

 jimtitt 14 Jan 2022
In reply to Pedro50:

The heating engineer sitting next to me as we drink our after-work beer says;-

Pro's, good retrofit for properties with normal rads, if one system goes down the other keeps going, "normal" hot water supply and you can play the energy price changes.

Cons, higher initial cost, the interlinking is more complex and the service costs are higher.

They are sold by all the major manufacturers here in Germany but my buddy says he's never installed one in a new-build, only as retrofit where there was an existing gas/oil system

I've pondered on fitting a ground source pump into my existing pellet/wood system but the price of electricity puts me off.

 Philip 14 Jan 2022
In reply to Ridge:

> I can't imagine the ASHP bit being much anyway use in a house with a D EPC rating.

D or above needed for RHI scheme and ASP. I got my house from E to D, ASHP worked fine. Properly done mine would be at least a C now, but the method to calculate used in 2014 was flawed for modern heating / hot water.

1
 mjc1010 14 Jan 2022
In reply to Pedro50:

I had the Daikin version of this installed last year, through a trial so was free. I've been quite impressed with it as a system. I'm in a late Victorian end of terrace with no cavity wall insulation but reasonable loft insulation and double glazed windows, so not a super insulated house and it has kept the house warm enough, but the more insulation the better I’d say. When it’s cold outside then the gas boiler operates and if it’s warmer then the ASHP comes on, I’ve got it set to minimise cost (you can enter the electricity and gas prices and it calculates what’s the cheapest energy source to use) and I think the change over for my fuel price combination works out at about 6 degrees external temperature. Mine also has weather compensation so it changes the temperature of the circulating water depending on the outside temperature, this can also be tweaked depending on how your house behaves, which would also change when the gas boiler would operate, but I’ve not changed mine from the default settings. You need larger radiators for when the heat pump is on to provide enough heat as it circulates lower temperature water. Also a bit of a change of mind set, as when the heat pump is running it doesn’t warm up quickly so heating on for longer and not letting the house get as cold when you’re not in. Whilst it’s "2 systems in one" when offered it I thought this was a way to move to a lower carbon heating system but still have the safety blanket of a gas boiler in case the ASHP struggled in an older house.

In reply to mjc1010:

I take it you can switch over to gas if you want a quicker boost of heat?

Are they in anyway future proofed for hydrogen? Probably too early for that, but certainly something to consider when making big investments that might last 15-20 years. 

 mjc1010 16 Jan 2022
In reply to Alasdair Fulton:

It doesn't have a boost button to put it on gas, it just goes off the thermostat saying it needs heat then bases which one to turn on based on the conditions. I guess they want to avoid an override button as people will just use it all the time.

Not sure about hydrogen.

 mutt 16 Jan 2022
In reply to Alasdair Fulton:

didn't the OP state that this was for FREE! ASHP run at considerably lower cost right. Gas is a nice to have when the ASHP can't produce enough heat. Surely one should not look a gift horse in the mouth. lets not bother ourselves with a critique of  this system when no other is available at £0 other than sticking with what the OP has now. I'm guessing that is gas. And gas prices are going through the roof and are predicted to be so for 2 or more years. 


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