ASHP and LPG

[GMH]

I have a holiday cottage in a remote location without mains gas. The lpg hot water / central heating system has a recently installed high efficiency condensing boiler. I don't have space for a large lpg tank so use the 47kg bottles and these are expensive. The cottage is getting through a great deal of pg and gaining access to the property in severe weather is difficult so lpg deliveries aren't guaranteed. As the cottage is let I don't really want paying guests freezing..
The cottage will be well insulated (still needs to be finished) and has double glazing throughout. Unfortunately it has wooden floorboards but these are covered throughout with the aim of minimising drafts. Cavity wall insulation still to be installed but this is planned.
I am looking to possibly install an ASHP as the main source of energy for hot water and central heating. I know I need to oversize the radiators, these need replacing anyway.

I am thinking of using installing an ASHP in such a way as to allow switching between ASHP and lpg boiler. ASHP used mainly, but for the lpg boiler to provide a manual boost (possibly via the Internet as I live 300 miles away) in extreme weather conditions when it is least efficient and when the lower radiator temperature isn't sufficient to heat the house. I don't like to heat the cottage unnecessarily so to keep it ticking along when it isn't let is probably ideal via an ASHP with the thermostat set low.

I am thinking of installing a Daikin Altherma monobloc LT ASHP. One of the new 8kW units should be adequate, although I will seek advice on this - 3 bed semi-detached bungalow. BTW - not enough space for a GSHP and not really enough space for an indoor unit to accompany the ASHP.

I'm not a plumber, but enthusiastic amateur!

Do you know if this approach has been done before?
Do you see any problems with it?

I have a general question about ASHPs. I understand that the COP changes with temperature. If an ASHP is rated at 8kW will it always give 8kW over the temperature range -10 to +25C and just demand more input power, or does the input power remain the same but the output drops?

Another general query - can radiators be fan assisted rather than oversizing them?

 

[ecowarm]

I have a holiday cottage in a remote location without mains gas. The lpg hot water / central heating system has a recently installed high efficiency condensing boiler. I don't have space for a large lpg tank so use the 47kg bottles and these are expensive. The cottage is getting through a great deal of pg and gaining access to the property in severe weather is difficult so lpg deliveries aren't guaranteed. As the cottage is let I don't really want paying guests freezing..

Good idea and an Ashp will be alot cheaper to run than bottled LPG

The cottage will be well insulated (still needs to be finished) and has double glazing throughout. Unfortunately it has wooden floorboards but these are covered throughout with the aim of minimising drafts. Cavity wall insulation still to be installed but this is planned.
As much insulation as possible

I am looking to possibly install an ASHP as the main source of energy for hot water and central heating. I know I need to oversize the radiators, these need replacing anyway.

I am thinking of using installing an ASHP in such a way as to allow switching between ASHP and lpg boiler. ASHP used mainly, but for the lpg boiler to provide a manual boost (possibly via the Internet as I live 300 miles away) in extreme weather conditions when it is least efficient and when the lower radiator temperature isn't sufficient to heat the house. I don't like to heat the cottage unnecessarily so to keep it ticking along when it isn't let is probably ideal via an ASHP with the thermostat set low.

Controled by room stat and out side temp sensor (weather comp)

I am thinking of installing a Daikin Altherma monobloc LT ASHP. One of the new 8kW units should be adequate, although I will seek advice on this - 3 bed semi-detached bungalow. BTW - not enough space for a GSHP and not really enough space for an indoor unit to accompany the ASHP.

Other good makes on the market and not so expensive

I'm not a plumber, but enthusiastic amateur!

Not a job realy for an amature but you could help a proffesional to keep the cost down

Do you know if this approach has been done before? Yes
Do you see any problems with it? Not with a good ASHP company with good technical back up

I have a general question about ASHPs. I understand that the COP changes with temperature. If an ASHP is rated at 8kW will it always give 8kW over the temperature range -10 to +25C and just demand more input power, or does the input power remain the same but the output drops?

All ASHP performance drop the lower the outside temperature

Another general query - can radiators be fan assisted rather than oversizing them? Yes Fan coil rads are a good option with heat pumps

I will PM you with the contact details of a very helpful ASHP manufaturerer

Eco

 

[blue moon]

i have an eco dan 8.5kw running my house and if you get the rads sized correctly you shouldnt need anyback up really, ive had mine in since sept 2009 and been through 2 bad winters and its been minus 15 where i live. you do really want an mcs accredited fitter to do the work and then you will be eligible for the (rhi) renewable heat incentive which meens you should make money out of the heating, drop me a line if you want any help 01457 858081

 

[mooreofdevizes]

Daikin ASHP are by far and away the best on the market. They have a new ASHP on the market that takes the temperature up to 80deg. no need to change rads or worry about not coping in extreme cold. Be aware that all ASHP outputs are quoted with an outside temperature of 7deg. so lower outside temperature lower output.

 

[GMH]

Thanks for the responses. Is anyone able to respond to this particular question?

If an ASHP is rated at 8kW will it always give 8kW over the temperature range -10 to +25C and just demand more input power, or does the input power remain the same but the output drops?

I suspect it just demands more input power..

 

[ecowarm]

Thanks for the responses. Is anyone able to respond to this particular question?

If an ASHP is rated at 8kW will it always give 8kW over the temperature range -10 to +25C and just demand more input power, or does the input power remain the same but the output drops?

I suspect it just demands more input power..

A 8kw ashp at 7c may only give 4kw at -7 ....... lower the temp the lower the output ......... it does depend on the make....... also watch out some makes have built in back up immersion heater and are very expensive to run £££££

 

[mooreofdevizes]

Ecowarm is quite right some do have back up heaters but you can schedule them to stay on for however long you want. They are used to pre-heat the water to about 16deg before the heat pump kicks in.