ASHP – Should do better - Must Do Better

lovesgshp

expertise of installer should be sought like any other major investment, either from word of mouth or by recommendation, or from the MCS database, or on the 'find an installer' part of the manufacturers website. Look for a company that doesn't just specify one brand.

Very true, also check how long they have been engaged in the activity, certification and specialisation. Must admit that we use only one manufacturer, but they have over 300,000 units operating in Europe and have a history of developing heat pumps going back to the 1970's. They would not use the Mitsu scroll compressor until it was developed to confirm to their standards, which now has over 30 patents and they are the only company that can use this unit.

Cardew

albyota wrote: »

The COP of any of the equipment will be annual COP at x external temp and x water temp.

Albyota,

Isn't that the problem!

Lots of systems just don't approach those theoretical figures.

Graham above mentioned the defrosting cycle - which in at least a couple of the specialist websites is given as 'the killer for ASHPs.'

It would be very easy to take the theoretical COPs plotted against ambient temperatures over a 12 month period and I would wager that a COP of 3+ would be obtained for all marketed systems. However on the EST trial several systems were 1.6 or less.

Looking at the latest Misubishi Ecodan website I found these extraordinary statements

The reduction in energy bills compared to gas, mean that the system can pay for itself within 2 – 3 years

* In independent tests carried out by the Building Research Establishment, BRE, Ecodan was found to reduce emissions by 50% and running costs by 30% in comparison to a modern gas boiler.

Now it is my understanding that an average Ecodan system costs in the region of £6,000.

The new revised average annual gas consumption in UK is approx 16,000kWh(was 20,500kWh pa) so a gas user will pay around £500 to £600 pa for all heating and hot water.

So if £6,000 is a reasonable figure, one wonders how it saves £2,000 to £3000 a year in energy bills to 'pay for itself'.

rhiwfield

Thanks Cardew, from my reading the sites were chosen by EST, and certain systems underperformance was not explained (not good). But I got no sense of manufacturers/installers interfering during the trial period. Interestingly most installs were retrofits.

The better ASHPs had pump COPs of 3.3 and system COPs of 3.2 with the mean (I think) at 2.3 and 2.2 respectively. Whereas I'd be very happy with a system COP of 3.2 I'd be disappointed at a system COP of 2.2 and livid at the one worst performing system at 1.2!

But if I dont upsize my rads I'll need to run pump at high temps and lose out on COP. And with system performance being weather dependent, if the back up system is designed to cut in correctly, the heat pump COP should increase, though only applicable to the 80-90% of time it is heating the home.

So a quick question for Albyota (and pls be aware that I've asked for, but not yet received, a quote from ACS), with correctly sized rads, a heat requirement of 16kw, and a bivalent approach what would be the system COP (and preferred heat pump) you'd expect for a space heating only heat pump, either doing 100% or using oil boiler for bivalent approach.

lovesgshp

Cardew.
I have just had a look at the consultants Earth Energy, and they seem to only specialise in gshp installation. I could not find any reference to ashps.
From their website:
brighter people, cleaner future

reliable, sustainable, affordable, renewable ground source, available


EarthEnergy Limited, have been designing, specifying and installing ground source heat pump systems in the UK almost twice as long as any other UK company.


Over the past 15 years we have installed nearly 2,000 systems, connected to 200km of boreholes, which together save 6,000 tonnes of CO2 every year, the equivalent of about half a million trees.

bobmedley

http://www.elisanet.fi/sanyoco2log/

I have had a quote of £10k to install one of these Sanyo systems

Cardew

rhiwfield wrote: »

The better ASHPs had pump COPs of 3.3 and system COPs of 3.2 with the mean (I think) at 2.3 and 2.2 respectively. Whereas I'd be very happy with a system COP of 3.2 I'd be disappointed at a system COP of 2.2 and livid at the one worst performing system at 1.2!

Actually there is a discrepancy in those figures IMO.

If you look at the ASHP COP results on page 15 they list all the systems(actually only 28 results of the 29 tested)

However for six of the systems for some unexplained reason they were not able to measure their results so they gave estimated COPs. Those six systems were estimated at being well above the average COP - the three top systems with a COP of 3.2 were all estimated and not measured, and the other three were also well above average as well.

So if you take the average of all the measured systems the average COP is below 2.0.

It is also pertinent to mention(yet again!) that these disappointing figures are even worse in practice(because of the low water temperatures) ASHPs have to be run for long periods producing heat when the occupants are out or in bed.

Cardew

bobmedley wrote: »

http://www.elisanet.fi/sanyoco2log/

I have had a quote of £10k to install one of these Sanyo systems

Thanks.

Ok so that is in Southern Finland, but the overall COP for the last 24 hours of 1.18 and last month of 1.2 is terrible IMO. The annual COP is 1.54.

Frankly you would be better sticking £10,000 in a long term savings account and getting 4.75%(£475 pa gross) and heating your house with panel heaters costing £hundreds - or even get storage heating.

rhiwfield

bobmedley wrote: »

http://www.elisanet.fi/sanyoco2log/

I have had a quote of £10k to install one of these Sanyo systems

here's some live data on air to water heat pumps

heat pump live data

lovesgshp

bobmedley wrote: »

http://www.elisanet.fi/sanyoco2log/

I have had a quote of £10k to install one of these Sanyo systems

You cannot really take data from someone in Finland, which has much more temperature extremes than the UK. The readings for the first chart are based on -5.1C so the cop will be much lower. His hot water temps are steady, showing the heat delta is working, with hot water priority, otherwise DHW production would not be kicking in as much.

lovesgshp

http://www.weather.com/outlook/travel/businesstraveler/wxclimatology/monthly/graph/FIXX0002

This is for Helsinki