Air Source Heat Pumps

Andy_WSM

mech wrote: »

Consumption isn't the issue; I believe you on that, but it doesn't tell us much because we don't have anything to compare it to. I could post meticulously collected gas consumption figures from my house and they'd look a lot cheaper, but it isn't the same house in the same location, so still tells us nothing.

I've posted this before, but here are my own results after 1 year of running an air to water heat pump in place of an old (5 years old) combi-boiler.



I took the gamble that the air to water pump was going to work as well as the manufacturers claims - and it does and still continues to do so 18 months on.

Same house, same levels of insulation - in fact, same radiators (something that others claim won't work).

edit - wanted to add that as 2009 hasn't been significantly colder or warmer than 2008 in the UK, for all intents & purposes the operating temperatures are the same over the 1 year period - although January saw the coldest spell of weather for near on 20 years in this area, so the savings might have been even greater (better COP).

stevehead

mech wrote: »

No real-world test has reported a seasonal COP of 4 or more with an air-to-air heat pump. If I'm wrong on that statement find me the test that bucks the trend.

The COP value stated by reputable manufacturers is not taken from a spot measurement, it is taken over time but with a constant outdoor temp of 7C.
No, I can't find you a link to a test that shows a COP of over 4, and that's because I can't find a test of any unit which claims to have a COP of >4 in the first place.

The interesting figures are seasonaly corrected vs stated COP (@ 7C).
For example, the Ecodan has a COP of 3.85 'in the lab' whereas UK field trials show it gives a seasonally ajusted COP of 3.25. This means that we can use a formula of COP X 0.84 to get the likely UK performance.
This is the same method as the beloved SEDBUK; take manufacturers lab claim and crunch it through a UK Seasonal Ajustment formula.
Oh, and not forgetting that SEDBUK does not take into account DHW, whereas the Ecodan field trial does.

"From data provided by BRE testing (the UK's leading centre for independent advice for the built environment) and from case study analysis running costs can be reduced over a conventional gas boiler by approximately 35%. These saving are achieved using standard tariff electricity."

Cardew

stevehead wrote: »

"From data provided by BRE testing (the UK's leading centre for independent advice for the built environment) and from case study analysis running costs can be reduced over a conventional gas boiler by approximately 35%. These saving are achieved using standard tariff electricity."

One aspect that has to be considered is any 'wasted' heat.

For instance storage heaters, like all electrical heaters, are 100% efficient. However their big disadvantage is that the leak heat, both during the night whilst 'charging' with heat, and during the day when the heat may not be required.

To a lesser extent that can be considered a disadvantage with heat pumps in that they are best utilized keeping an even temperature during the day. Unlike a high output gas/oil CH(with water at 80+C) which can be set to warm up a room very quickly.

richardc1983

Well guys not sure how all your systems are doing but my air to air system is coping fine, havent even had a defrost yet...

Its -0.2 here, very cold indeed... had a few flakes of snow here and a toasty 22C throughout the flat, has held that temp from about 15:30. At 1pm it was 16C! Unit hasnt cycled off though its just kept running.

stevehead

Are the defrost cycles the major COP Killer, or is there anything else to consider? (within the performance envelope of the refrigerant)

PS 7.3C here, 4pm

richardc1983

I cant believe how warm it is where you are.

For me the defrost cycles are what make the system perform bad, its just done its first defrost lasting 3minutes but it will be another 2 mins before it starts blowing warm again.

Whilst the flat is 22C throughout its a victorian building and does get very cold. I.e the thermometer that was reading 22C on the wall (digital) is now reading 20C within 5mins so it drops very quick, The room temp measured in the middle is reading 21.6 whereas 5minutes ago it was bang on 22C so the system has to work hard to achieve its temperatures when its as cold as this.

Its not cycled off today and 1 defrost cycle in 4 hours is very good.

The system being oversized is a good thing too I see as it means fan speeds can be run in low and it also has that extra duty for times like these where I can bump the fan speed up should I need it.

stevehead

Very clear still day but I expect the temp to plummet tonight. Still only had 1 frost this winter ie ice on the car in the morning. Even today it was 4C when I did my first callout at 9.00.
Victorian houses are fantastically spacious compared with my 60's rabbit hutch, a typical 3 bedroom vic house probably has twice the internal volume.

2 degree drop in 5 mins rich!! Did you have both front and back doors open at the time?

richardc1983

No thats just how poorly insulated these places are, below me is a cellar that is freezing cold and no insulation in teh floor, and above are other flats that dont have heating during the day, theres only me with heating the others rely on communal heating at set times!

clockworks_2

Hi

I have recently moved into a new build flat made by Comer Homes which has an air source heat pump. All of the flats here have them. It is one main unit in the bathroom which then vents out to all the rooms in the flat via small round vents in the ceiling.

You can't control individual rooms - it's a system which heats up the whole flat at once. It's been fine so far but over the past 2 days i am really struggling to warm the flat.

The unit is controlled by a remote control and i have even set the remote at 30 degrees but even then the flat struggles to over 18 degrees. I was under the impression there was an electric filament which warmed up for extreme cold temperatures but if so it's not much use.

I have recently had the unit serviced about 6 weeks back and the serviceman said it was in fine condition with out the need for any further work.

The flat is extremely well insulated with no draughts.

Any idea what i can do or should do to warm the flat up more? Or will i have to resort to electric heaters in each room?

Thanks

richardc1983

clockworks wrote: »

Hi

I have recently moved into a new build flat made by Comer Homes which has an air source heat pump. All of the flats here have them. It is one main unit in the bathroom which then vents out to all the rooms in the flat via small round vents in the ceiling.

You can't control individual rooms - it's a system which heats up the whole flat at once. It's been fine so far but over the past 2 days i am really struggling to warm the flat.

The unit is controlled by a remote control and i have even set the remote at 30 degrees but even then the flat struggles to over 18 degrees. I was under the impression there was an electric filament which warmed up for extreme cold temperatures but if so it's not much use.

I have recently had the unit serviced about 6 weeks back and the serviceman said it was in fine condition with out the need for any further work.

The flat is extremely well insulated with no draughts.

Any idea what i can do or should do to warm the flat up more? Or will i have to resort to electric heaters in each room?

Thanks

Can you increase the fan speed? When its colder you may need higher airflow to move more heat in, failing that you need to get the guy back out.

Do you have a make and model of the system that you have installed?