ASHP yay or nay?

Hels888

Hi
We could do with some advice from Air Source Heat Pump users. Have trawled all the forums but a lot of the discussion dates back 7 or 8 years and can't seem to find recent unbiased reviews.

We are looking at getting one installed in a 5 bed detached house built in 2003. Currently have communal lpg and radiators. The plan would be to use the EDF offer of installing an ASHP in line with the current lpg boiler and radiators. It uses passivsystems controls.

Would really appreciate some help from users on what you realistically get in terms of coefficient of performance average through the year in the UK. We suspect we won't save much if anything when you factor in the additional maintenance costs. Will be a Samsung 8kw.

Also how noisy are they in reality? I know the figures state around 60db and they're working harder in the cold when you're in the house anyway but we've seen scare stories of upset neighbours. We live in an almost silent close and are about 8 metres from the next door property. Have seen the covers you can buy but no idea if they achieve the benefits they claim?

Any help would be much appreciated. 

Thank you
Helen

Cardew

Welcome to the forum.

What do you mean by 'unbiased views'?

On an internet forum you are bound to get a range of opinions from highly enthusiastic, to highly un-enthusiastic - so are both those extremes 'biased?

Some years ago the EST commissioned a 12 month trial of loads of ASHP's(the link can be found on this forum) and the results were little short of a disaster, so they got all the manufacturers involved to sort out their installations and carried out another 12 month trial; and the results were still IMO a disappointment, the average system COP was well below 3.0.

It is no use asking owners what COP their system achieves; how would they know? 

Hels888

Cardew said:

Welcome to the forum.

What do you mean by 'unbiased views'?

On an internet forum you are bound to get a range of opinions from highly enthusiastic, to highly un-enthusiastic - so are both those extremes 'biased?

Some years ago the EST commissioned a 12 month trial of loads of ASHP's(the link can be found on this forum) and the results were little short of a disaster, so they got all the manufacturers involved to sort out their installations and carried out another 12 month trial; and the results were still IMO a disappointment, the average system COP was well below 3.0.

It is no use asking owners what COP their system achieves; how would they know? 

Hi Cardew
Thanks for the response.

In terms of unbiased most of the reviews online are on websites about grants, manufacturers or have links to discounts. Opinions very much welcome, just didn't fancy a sales pitch! 

I saw that report but it was years ago as you say and I'm interested to see if the technology has moved on. We were hoping users should be able to tell at least if they are using the units of energy they were quoted and the assumed COP used to calculate the quote to see how closely they align. 

Cardew

I have not seen any company claiming any significant increase in efficiency, other than the ability to produce better results at outside temperatures not experienced in UK. A quick look at the specifications of a couple of manufacturers seem - from memory - approx the same as 10 years ago. I am not a Physicist but isn't there a finite limit on the ability to extract heat - Carnot cycle?

If you read various websites it seems a SYSTEM COP of 3.0 is good. Given electricity costs around 14p/kWh a COP of 3.0 means a kWh costs 4.67p. Thus not competitive against gas or oil at today's prices.

The disadvantages of an ASHP are the same today as years ago.

You need extra large radiators or underfloor heating to utilize the low temperature of water necessary for efficiency. Thus Difficult/expensive for a retrofit.

Requirement to run for very long periods or 24/7. OK if you are home all day, but heating an empty house if you are out.

Hels888

Thanks Cardew
Anyone got an ASHP installed who can weigh in? 

Gerry1

Hels888 said:

Anyone got an ASHP installed who can weigh in? 

Search @matelodave's posts, there's much useful info there.

matelodave

Yup, I've got an air source heatpump - an 11kw Daikin feeding a 140sq.m detached bungalow with three bedrooms and we've had it for over ten years. We've got overlay wet underfloor heating and 200litre hot water tank.  We are more than happy with it's performance and running costs but you must get the whole system designed properly.

They dont work like a conventional boiler and run  at much lower flow and return temperatures so need to run a lot longer and need larger radiators. They aren't suited to on-off operation like a high temperature gas or oil boiler and can be very slow to respond (ours can take a 24-36 hours to reheat the house if we let it get stone cold).. It's operation suits us as we are at home all day but we don't shut it down overnight, just set the thermostats back by around 2-3 degrees.

Just hooking one onto an existing system will be a recipe for disaster. Proper unit sizing, pipework, radiator sizing,controls, commissioning and operation all have to be finely balanced to get the best out of one. Understanding how it all goes together and, most importantly, how to use it properly can be the difference between satisfaction and despair.

danrv

Cardew said:

The disadvantages of an ASHP are the same today as years ago.

You need extra large radiators or underfloor heating to utilize the low temperature of water necessary for efficiency. Thus Difficult/expensive for a retrofit.

Which does beg the question ‘why not consider air to air ASHP?’
Is it that they don’t qualify for RHI payments or maybe because a radiator system is more conventional.

Hels888

danrv said:

Cardew said:

The disadvantages of an ASHP are the same today as years ago.

You need extra large radiators or underfloor heating to utilize the low temperature of water necessary for efficiency. Thus Difficult/expensive for a retrofit.

Which does beg the question ‘why not consider air to air ASHP?’
Is it that they don’t qualify for RHI payments or maybe because a radiator system is more conventional.

Thanks danrv. We're only really interested due to an offer with EDF where they'll install for £399 and they force you into an air to water pump with current boiler retained. We don't think we would recover the costs quickly enough if we went for an air to air or an ASHP with underfloor heating system outright.

Hels888

matelodave said:

Yup, I've got an air source heatpump - an 11kw Daikin feeding a 140sq.m detached bungalow with three bedrooms and we've had it for over ten years. We've got overlay wet underfloor heating and 200litre hot water tank.  We are more than happy with it's performance and running costs but you must get the whole system designed properly.

They dont work like a conventional boiler and run  at much lower flow and return temperatures so need to run a lot longer and need larger radiators. They aren't suited to on-off operation like a high temperature gas or oil boiler and can be very slow to respond (ours can take a 24-36 hours to reheat the house if we let it get stone cold).. It's operation suits us as we are at home all day but we don't shut it down overnight, just set the thermostats back by around 2-3 degrees.

Just hooking one onto an existing system will be a recipe for disaster. Proper unit sizing, pipework, radiator sizing,controls, commissioning and operation all have to be finely balanced to get the best out of one. Understanding how it all goes together and, most importantly, how to use it properly can be the difference between satisfaction and despair.

Thanks matelodave, really good to know how you've found it. Your set up sounds far superior to what ours ever would be. Pretty confident we'd end up in the depths of despair, just a nagging doubt that it's worth a try for £399 through edf

danrv

Hels888 said:

danrv said:

We're only really interested due to an offer with EDF where they'll install for £399 

Surely £3999?