Hot water and heating

[Gasgavalar]

Hi everyone, My wife and I have downsized as we approach retirement. The bungalow we have bought is enabling us to renovate it to ensure we can future proof it. Stuck looking at heating options. Can’t decide whether you get an ASHP with a Mixergy tank supported by Solar PV or get a SAHP thermodynamic panel for hot water and an electric boiler to run our wet UFH. Any advice is welcomed.

[SteamyTea]

ASHP to do both space heating and DHW.

Then add PV.

 

Much of it depends on what you think is important. 

Constant supply of heat 

Cheapest installation price

Most reliable

Cheapest running costs

Least GHG emissions

Simplest to install 

And many more 

 

 

 

[JohnMo]

What is your current heating demand?

 

Have you looked at Exhaust Air Heat pump cylinders (heat pump and cylinder in one, such as the Dimplex edel for example.  They would be a standalone hot water solution which can also be heated with PV or solar solar thermal.

 

 

[Gasgavalar]

This for this JohnMo, Never heard of exhaust air heat pump cylinders. Time for more research 

[Gasgavalar]

Thanks for replying SteamyTea. I suppose I want all of what you listed which I suppose isn’t the electric boiler route?

 

[Radian]

How many kWh are you expecting to consume with the UFH each year? Electric boilers at £0.34/kWh - soon to be £0.50 (or who knows what) simply don't add up any more IMO. Tempting, I know, because of simplicity and super low equipment cost. But even if you ran a 3kW Willis heater for around one sixth of a day, over a 5 month period, that'd put £1K on your electricity from next April. And unless you cover the back garden in PV, you won't be getting any of that out of your PV.

[Gasgavalar]

Thanks for replying Radian. The UFH Company  suggest it will be a 5.8kW system. Whilst some electric boilers are low cost, I think like most things, it might be poor quality at basement price so even more unfavourable if spending a lot on the boiler 🤔

[JohnMo]

If your using 5.8kW on a cold day, that is 5.8x24=139kWh per day.  So £70 per day at £0.50 per kWh. An electric boiler will give you 1kWh out for each kWh in. Never any better than that. An electric boiler is really just an immersion heater with some control.

 

A heat pump on UFH should get a CoP of 3 or better on the coldest day, so would cost £23 per day instead of £70.  A typical heat pump 3kWh out for each kWh in.

[ProDave]

7 minutes ago, JohnMo said:

A heat pump on UFH should get a CoP of 3 or better on the coldest day, so would cost £23 per day instead of £70.  A typical heat pump 3kWh out for each kWh in.

I would be having kittens if I was paying £23 per day even with a heat pump.

[Radian]

This is why we need to know the losses that need to be made-up for with the UFH. If a company has spec'd a 5.8kW boiler I'd hope it wasn't expected to do a 100% duty cycle. But anything over 10% would be painfully expensive.

 

I'm going to get a reputation here and ask if air-to-air has been considered. COP 5 is commonly achieved.

[Adrian Walker]

6 hours ago, Gasgavalar said:

Hi everyone, My wife and I have downsized as we approach retirement. The bungalow we have bought is enabling us to renovate it to ensure we can future proof it. Stuck looking at heating options. Can’t decide whether you get an ASHP with a Mixergy tank supported by Solar PV or get a SAHP thermodynamic panel for hot water and an electric boiler to run our wet UFH. Any advice is welcomed.

 

I presume that you have looked at increasing the level of  insulation and airtightness first?

[Gasgavalar]

Never heard for air to air!

[Gasgavalar]

Thanks for replying Adrian. The doors and windows were appalling when we moved in so there’s have been replaced. I wasn’t sure about cavity wall, but a man with a horoscope has proved that we do have that done. We’ve just started lifting the floorboards and insulating the void as we have suspended floors and part of the renovation will be a loft extension, so that will be nicely insulated when finished.