ASHP – Should do better - Must Do Better

Cardew

At the risk of mortally offending the ASHP aficionados on this forum, there really must be something done about curbing the enthusiasm for this technology until the industry – manufacturers, installers or both - has come to grips with their problems.

A recent BBC report highlighted the poor performance of heat pumps and referred to the EST report for field trials on Heat pumps - particularly on ASHPs. http://www.energysavingtrust.org.uk/...mp-field-trial

Or try this http://www.energysavingtrust.org.uk/Media/node_1422/Getting-warmer-a-field-trial-of-heat-pumps-PDF

The study was a year long and had 29 ASHP systems from a number of manufacturers.(who installed the systems)

It is quite a long report but of the 29 ASHP systems the annual COP for 19 of the systems was 2.2 or less(the highest number had a COP of 1.6). So if that is an average spread across 12 months - little wonder systems are struggling in this current weather. In fact with the requirement for wasteful defrosting cycles, it is quite easy to envisage a situation with some systems where there will be a COP of less than 1.0 and people would be better to switch off the ASHP and rely on Granny's old 1/2/3 bar fire!!!!!!

It is also pertinent to point out(as I have before!!) that when considering the COP of ASHPs firms never take into account that the heat produced when occupants are out of the property, or in bed, is wasted. For instance it might be necessary to keep the ASHP running 24/7 because of the inability of the system with low temperature water to quickly bring the house up to temperature. It might be that, say, 30kWh will be produced when occupants are out or in bed.

With gas/oil CH with water at 80+C there is no need to heat the house when occupants are out/in bed, as 20-30 minutes will bring a house up to heat. Yet in the inevitable comparisons of running costs, the 'unwanted' 30kWh is always used to swing the comparison in favour of heat pumps – and still fails!

Now the trial was for 29 systems with the manufacturers involved over 12 months, all with a vested interest in getting good results and the results are frankly a disaster.

Virtually all the adverts talk of a COP(system efficiency) of 3 or greater, yet only one verified result achieved 3.0(there was an estimated 3.2)

Small wonder there are so many people on MSE complaining about their system’s performance and costs. Especially given there is normally reluctance for people to admit that something that has cost them £thousands is a disappointment.

It can’t just be the setting up of the system or none of the 29 systems in the trial – with the manufacturer at hand – would have performed so poorly; it must be more fundamental.

If the manufacturer monitored systems produced such poor results, I wonder what results a random check of properties with unsuitable or poorly installed systems would produce!!!

The ‘experiments’ owners are having to carry out in order to improve performance require some considerable technical knowledge. I shudder to think how many of the population could cope. The system should be set up by the installation company and be simple for the user to operate.

Frankly IMO it is irresponsible to recommend that anyone spends £thousands on installing an ASHP system where the results seem to be a lottery, and virtually nothing meets the manufacturer’s claimed performance.

retire_at_50_2

I think the introduction of the RHI will result in a lot more disappointed air to water heat pump owners. It seems users of air to air heatpumps are getting better results which is to be expected as the temp lift is lower. This is a specialised technology which requires a degree of technical ability to make it work effectively. The published COP figures are like showroom MPG numbers for cars, whats actually possible is often very different.

They are best suited to buildings with a low heating demand ie well insulated and draftproofed so that unfortunately excludes a lot of UK houses. I recently heard that across europe the UK has some of the lowest fuel prices but also has the highest fuel bills because the housing stock is so poor thermally. This also rules them out for intermittent use which tends to be the usage pattern of central heating here in the UK.

Ideally they are used with underfloor heating so lower water temperatures can be used improving COP but this has to be carefully designed to avoid long lags. While I can see the advantage of underfloor heating in consistently cold climates, here in the UK the weather is too variable. This can result in buildings being too cold at the start of a cold snap and then too hot when its finished. Retrofitting usually prevents the use of UFH so oversized radiators have to be used but care must be taken to ensure the lowest water temperature is used.

I collected a years temperature data here and using the operating figures (which are a bit thin on the ground overall) for a Daikin Altherma ASHP I calculated a COP of around 2.5 for the year. That was a mild winter so for the last 2 years it would be somewhat lower and I only calculated for space heating, using it for hot water I think would produce a large drop as the temp lift becomes excessive. A commercial installer confirmed I could expect a COP of around 2.5 using data from the nearest weather station. I used operating data based on heating+defrosting which is likely to be a problem in the damp UK.

Based on my theoretical experience if you are achieving a COP of over 2 with a retrofit ASHP you are doing well. While some of the poor performers in the report will be down to incorrect installation, I'm sure in a lot cases the heat pump is in the wrong building, its too large or too small (their output tends to drop as it gets colder - very difficult to size correctly) or its being used incorrectly by the user.

If you are considering installing an air-water heat pump do the sums very carefully, you need to know how much heat you house needs so it can be designed correctly. You will probably find you are better of with storage heaters.

Of course what we should all be doing is draftproofing and insulating our houses. This significantly reduces the heat demand (50-60% is possible) and as this happens it becomes increasingly irrelevant how you heat your house.

thechippy

TBH Cardew,

You do at least come across as trying to put these systems down when possible...;)

However, I have never been a lover of air to water systems and would not generally recommend them.

Air to air though, I firmly believe is the most efficient form of space heating. I would use on demand gas for hot water.

I've noted that you have mentioned several times that people may not be happy about leaving doors open etc to get the air movement, as in Steve Heads property. However, the first floor rooms could be supplied with a hidden ducted system which could supply each room.

On the ground floor, obviously either high or low wall mount systems would still be required, but they can look ok if installed with care and are not that unsightly.

welda

I was at a seminar late last year concerning domestic renewables, was a bit one sided with an amount of scare mongering, with lots of emphasis on dwindling hydro-carbons and NG, no doubt latter too elements will eventually run out, there are more and more new finds of HC & NG every day as technology increaes, unfortunately, cost will be high.

We need more nuclear power stations............pronto!!

:beer:

Andy_WSM

Well, I have to completely agree with Cardew having given up on my Trianco Air to Water pump this Winter and have had it decommissioned and replaced with a gas combi-boiler, which has, so far, been trouble free.

The heat pump was repeatedly freezing up, rendering it useless when it was needed most and I got fed up of days with a cold house and / or no hot water and bills that didn't reflect the lack of heat!

Yes, this Winter has been exceptionally cold, especially throughout December when the pump was as good as useless, consuming vast amounts of power for little return.

On the flip side, I do have a whole house, Fujitsu, air to air system, fitted primarily as air conditioning, but as it's a heat pump, can be used for heating too - it provided me with heat faultlessly during the transition period that the air to water pump was down awaiting a boiler to be fitted.

The difference in the 2 systems is likely the quality and the design spec. The Trianco is rated to -5C, the Fujitsu to -15C, so system choice should be considered VERY carefully before any system is fitted.

The reason it didn't seem so important here a few years ago when I made my purchasing decision is that I live on the coast, with a normal average Winter temperature of +7C. This last Winter has seen average temperatures of just +1C throughout December, with some exceptionally cold (-11C) nights. So, regardless of where you live I'd suggest any system is rated to cope with a worst case scenario, rather than the average seasonal temps.

It seems to me that gas boilers will carry on providing heat way beyond their system design temperatures, where as heat pumps cannot function beyond their design temperatures. i.e. at -10C a gas boiler will still run and provide heat into the house, but a heat pump may well freeze up and stop providing much, if any heat at all.

Cardew

thechippy wrote: »

TBH Cardew,

You do at least come across as trying to put these systems down when possible...;)

However, I have never been a lover of air to water systems and would not generally recommend them.

Air to air though, I firmly believe is the most efficient form of space heating. I would use on demand gas for hot water.

I've noted that you have mentioned several times that people may not be happy about leaving doors open etc to get the air movement, as in Steve Heads property. However, the first floor rooms could be supplied with a hidden ducted system which could supply each room.

On the ground floor, obviously either high or low wall mount systems would still be required, but they can look ok if installed with care and are not that unsightly.

It is not so much ‘putting these systems down’ as to curb the unbridled enthusiasm for the systems – particularly on MSE.

In fact you rather make my point for me when you , as someone who fits these system and is obviously knowledgeable, do not recommend Air to Water systems.

I had a property abroad with Air to Air. However that property was designed for the system with ducting and vents in every room, including toilets, bathrooms etc.

However to retrofit Air to Air I suggest is simply not an option for most people, where it is necessary to leave doors open including toilets, bathrooms etc!!! or have multiple units around the property. Also whilst relatively quiet it is disconcerting to have the noise from fans.

I am also not sure that the problems associated with defrosting Air to Air are fully solved in UK.

Notwithstanding your valid points on Air to Air, that is not the way the industry is going. The vast majority of systems seem to be Air to Water – e.g. Mitsubishi Ecodan etc - and surely nobody can argue that with these systems the whole industry has problems in achieving satisfactory results.

muckybutt

Getting rid of our Heatking 9000i http://www.heatking.co.uk/products/bwarmi-range/ its one of the worst decisions we've ever made getting one of these things just thankfull we got it all for free as a grant. Last year 70 days worth of electric cost us nigh on £800 with us being told to keep it on permanently. This year it is its second year and we've just had enough with it, were going for a wood pellet boiler instead, our leccy bills before we had this heap of pish put in were approx £130 a quarter for winter months.

So anyone up Yorkshire way that wants a ASHP second hand but in full working order pm me im open to offers

Cardew

muckybutt wrote: »

Getting rid of our Heatking 9000i http://www.heatking.co.uk/products/bwarmi-range/ its one of the worst decisions we've ever made getting one of these things just thankfull we got it all for free as a grant. Last year 70 days worth of electric cost us nigh on £800 with us being told to keep it on permanently. This year it is its second year and we've just had enough with it, were going for a wood pellet boiler instead, our leccy bills before we had this heap of pish put in were approx £130 a quarter for winter months.

So anyone up Yorkshire way that wants a ASHP second hand but in full working order pm me im open to offers

Getting rid of? or getting?

thechippy

@Cardew,

I agree with some of your points.
Not all properties are suitable to retrofit to air to air.

Ours however, would be easy. All upstairs rooms could be ducted, so no open doors and downstairs could be taken care of by two wallmounts.

Regarding fan noise - that comes down to the quality of the system. Some have a "whisper" mode where the fans are amazingly quiet.

Even with air to air, I've lost count of the number of systems I've seen where they are just "thrown in" and not commissioned properly and / or have the incorrect refrigerant charge. People also have a habit (you can't blame them sometimes) for going for the cheaper systems which have a poor control strategy and do not meet the makers claims at low ambients.

The most common problem I've seen with air to water systems, is that they were undersized in the first place.
TBH, I genuinely feel that some companies do this on purpose to get the job by having the cheaper quote (especially if they are installing during warmer weather). By the time the very cold weather arrives and the client realises it doesn't work, the installers have been paid and don't care.

And yes, you're right - I'm not a big fan of these systems at all.

EDIT.

I've never installed an air to water system. As the refrigeration side is self contained, they are quite often installed by plumbers / heating engineers. I just get called out to them sometimes when the refrigeration side is faulty - the heat pump itself and not the plumbing side of things, although I've installed hundreds of air to air systems.

Cardew

thechippy,

The EST field trial of 29 systems, even with the manufacturers involved in the trial, produced dreadful results. So that involvement should have eliminated most of the criticisms you highlight of incorrect sizing/installation.

Just think what the results could be without the manufacturer's supervision - several horror tales on MSE.

In any case, even with the poor performance of many of those systems, those results are still inflated by the need for the systems to run continuously producing heat when not required.

You mention in your first post that with Air to Air that Domestic Hot Water should be produced by 'on demand gas'. The problem is that ASHPs are being promoted as the perfect solution for properties without gas; so hot water will be produced by immersion heater.

It is not my intent to make this the 'ASHP knocking' thread, but people are spending several thousands of pounds on systems, many of which will fall far short of their expectations and there should be some awareness of the situation.

'Retire at 50' in post #2 made the analogy of COP figures to the showroom MPG figures. Well we are all aware that the claimed 60mpg is rarely achieved. However at least all cars are subjected to the same rigorous standard tests for MPG and CO2 emissions and we have some data on which to work. Yet there are no tests for ASHPs. All manufacturer's make claims for their systems to be in excess of 3.0 and talk glibly of 3 or 4 units output for 1 unit input, yet do not have to subject their systems for testing.

thechippy

Yes I agree.

Some correctly installed and sized systems don't seem to perform either. It's just the ones I've looked at personally were undersized anyway.

As you say, if no gas is available, then water would still be by immersion. I was just pointing out that if I had the choice (if refurbing the house for example) I would go air to air and on demand gas as the ideal (IMHO)

I was in Spain recently where a lot of properties used on demand gas boilers for water, and are designed for low pressure bottled gas. They seemed to work very well indeed and from the few people I spoke to, were not too expensive to run.