Air Source Heat Pump Renewable Heating?

[PermaChanged]

Good to know, thanks

 

[tonys]

The immersion on our system is only used about once a week to heat the tank to make sure there is no legionnaires bacteria.

 

[dirtychinchilla]

I suppose in hindsight I don't need the 75c flow temps, as long as the ASHP is indirectly heating water for the hot water cylinder to 60/65 all's well - or even lower if I want hit higher SCOP and top up water temps with the immersion.

Flow temperatures for the UFH are lower, but this water temp is controlled by the manifold by mixing hot and cold together.

Why so high? You could probably go lower and an electric boiler (ideally, immersion isn’t great) to top up.

 

[PermaChanged]

Why so high?

Naivety and ignorance primarily I'm assuming

The only thing I know is that the stored water needs to at some point be raised to over 60c to kill off legionella, I'm also aware that my flow temperatures for UFH needs to around 45/50c.

From your questioning, I assume it'll be cheaper to run the ASHP at lower temps and top up the hot water with further heat, rather than running the heat pump at 60c+. Is this what you'd advise?

 

[dirtychinchilla]

Naivety and ignorance primarily I'm assuming

The only thing I know is that the stored water needs to at some point be raised to over 60c to kill off legionella, I'm also aware that my flow temperatures for UFH needs to around 45/50c.

From your questioning, I assume it'll be cheaper to run the ASHP at lower temps and top up the hot water with further heat, rather than running the heat pump at 60c+. Is this what you'd advise?

So there’s two things here, domestic hot water and heating. For domestic hot water, yes you need to pasteurise the water occasionally. This could be done without the heat pump and I think it’s something can be done once or twice a week (not 100% sure in the frequency).

Why run your heat pump for something that happens once or twice a week? Higher temperatures reduce the COP. So, I would aim to have it set to deliver the heating flow temperature and look to use an electric boiler or simile to pasteurise the domestic hot water.

I think you’ll need to speak to a specialist about all of this. But generally domestic hot water storage is the enemy of heat pumps.

 

[Coran]

Is 14kw recommended due to being on traditional, but enlarged, radiators?

Our property is not classed as small with approximately 125 sq/m of underfloor heating area, and apparently only need a 7kw heat pump. I'm wondering whether this is because of the large area of heating at low temperatures or whether it's insulation level based, or is your house huge?

I think it’s a mix of everything. It’s a detached 1930s house so minimal insulation (although I’m working on changing that!) over about 200 sqm of heated space. It was also an indicative quote before a heat survey (which I’m still waiting on results for).

Realistically, it’s probably more than I need especially with my room by room zone control but I think that to be MCS certified, the ASHP needs to be capable of heating and maintaining the temperature of the whole house at set temps per type of room e.g. 21C for a living room and 19C for a bedroom which is more than I would have them at. I’d guess this includes heating the conservatory in the depths of winter too…

 

[Adam_151]

I’d guess this includes heating the conservatory in the depths of winter too…

I think that is thing that won't be a requirement, converatories arn't meant to be on the main house heating system, its due to the inability of conservatories to meet the required U values with all the expense of glass, so they are allowed not to provided they are not technically part of the house, so external door between house and conservatory and separate heating*

*You see lots with electric panel heaters, which are probably the worst way to heat such a space... but are cheap!. Aircon running in heatpump mode is much better, but much dearer to install

 

[Coran]

I think that is thing that won't be a requirement, converatories arn't meant to be on the main house heating system, its due to the inability of conservatories to meet the required U values with all the expense of glass, so they are allowed not to provided they are not technically part of the house, so external door between house and conservatory and separate heating*

That makes sense. My conservatory has 2 radiators on the main central heating. I use zonal controls to keep them off except a few hours on weekend afternoons when my kid plays out there. Sounds like that may affect things?