Air Source Heat Pump - Efficient or Not - real data

[Tomr182]

Hi all

I've had an ASHP for 10 months now, and thought I would share some data. Hopefully its interesting for anybody considering it, and also anybody else who may be getting better or worse and keen to share any settings to improve the efficiency.

I live in a 4 bedroom, detached house, north east of England, Samsung 5kWh ASHP, 200 litre tank with a 50 litre as well, heating with radiators that were increased in size. A 1 year old in the house, so baths a plenty (grrrrr)

Anyway, I'm no statistician so I'll try to explain what I have done. I have recorded the information from the control panel, for every single day since it was installed. Recording both the energy used (column 1), and the energy generated (column 2), and just dividing one by the other to find the efficiency level (column 3).

Part 1
If I take all the daily information and average 'column 3', I am running at 2.99

Part 2
If I total column 1 (energy used) and column 2 (energy generated) I get 2.53

Part 3
Jan - March average of column c. I get 2.65. A worst single day of 1.43 and a best day of 3.41
April - June average of column c. I get 2.78. A worst single day of 1.02 and a best day of 4.69
July - Sep average of column c. I get 3.51. A worst single day of 1.21 and a best day of 5.00

The bit that baffles me slightly, is the worst days, they are always a Tuesday, and that is the day the ASHP does its 'water law' of heating to 65 degrees, every single week. It absolutely destroys efficiency given 14% of the year as its every Tuesday, all year round, the efficiency is as best 1.43. And that's only because its a cold day so using energy to give heat as well.

So, in my summary, I would say I'm running at 2.53 average effiency which I don't actually think is that good. If I take out all the Tuesdays, I get the average up to 2.71 using the Part 2 method. The Part 1 method I get 3.08.

Anyway, I can slice and dice if anybody wants it in a different way, but thought I would share the findings. My ASHP is running at 2.53 efficiency in its first 10 months.

 

[binky]

Makes you wonder if you can change Tuesdays from weekly to monthly?

One of the things that bugs me is linking electricity prices to gas,when generation from wind and solar is so much cheaper. For the ' all electric' future, cheap electric is essential

 

[ProDave]

On another forum I had a discussion about this, and the conclusion was if you have treated mains water, you can trust that there will be no bacteria entering your hot water tank.

If your hot water tank is an unvented cylinder, which it is, you can trust that there is no other way for bacteria to enter your tank.

Thus the need to heat the water to 65C once a week is an urban myth. You DO need to do that if you are on a private water supply of have a vented hot water tank fed from a cold water header tank.

My hot water only ever gets heated to 48C by the heat pump. It will often get heated hotter by the immersion heater soaking up surplus solar PV generation, but that is at no cost.

 

[Tomr182]

Loving the escalation of suggestions haha
From weekly to monthly to not at all. Makes you wonder why companies set it up like that on install

 

[Geoff1946]

The need to heat the water to 65 degrees is allegedly to kill Legionella bacteria. This will only work if ALL the water is so heated.
Hence if the bottom of the tank remains relatively cool this provides a breeding ground for the bacteria, so heating by immersion element will only work if a de-stratification pump is also fitted.
On the other hand I do wonder if the risk is greatly overplayed in UK. I know there have been casualties, but I suspect these resulted from rare system malfunctions or from neglected wet air conditioning coolers. When travelling to warm countries I see water systems on house roofs, in the sun, and supply pipes only partially buried. Neither of these would be acceptable under UK Legionella guidelines.

 

[arwooldridge]

The need to heat the water to 65 degrees is allegedly to kill Legionella bacteria.

The alternative is an indirect hot water system. We have that, although it's a GHSP. Hot water is confined to a closed system heat store. Domestic hot water is then drawn direct from the cold water mains passing through a heat exchanger. It does away with the need for a domestic hot water tank. Fairly sure it's also possible on ASHP's but obviously must be designed in from the start.

 

[johnb2713]

Loving the escalation of suggestions haha
From weekly to monthly to not at all. Makes you wonder why companies set it up like that on install

Crikey, no need for the sarcasm, people merely expressing their thoughts to try and assist you to improve efficiencies. Makes you wonder why companies set it up like that on install? probably because thats the default setup as done by the manufacturer to cover a wide range of installation configurations and environments and the grease monkeys doing the install dont know any better / havent researched the subject further.
Just as an aside, your first post you state "the energy generated (column 2)" heatpumps dont generate energy, they do as their name suggest, pump heat from one location to another.

 

[Chewbacca]

Loving the escalation of suggestions haha
From weekly to monthly to not at all. Makes you wonder why companies set it up like that on install

because someone told them too, and to cover there bums!

 

[binky]

e risk is greatly overplayed in UK. I know there have been casualties, but I suspect these resulted from rare system malfunctions or from neglected wet air conditioning coolers. When travelling to warm countries I see water systems on house roofs, in the sun, and supply pipes only partially buried. Neither of these would be acceptable under UK Legionella guidelines.

Originally it was old fashioned aircon systems that used to have water cooling towers exposed to the air that caused most problems. Since then it seems to have extended to any 'stale water' situation. The school I do jobs for run all the taps after holidays, before the kids return, and if away from home for an extended holiday, I tend to run taps, flush toilets etc to get clean fresh water back in the system. I'm not convinced I really need to do that, but water companies are increasingly using UV to treat water rather than chlorine, so you have to wonder how long water will remain potable? Article below is interesting.

https://mytapscore.com/blogs/tips-for-taps/stagnant-water-in-a-vacant-building

 

[Tomr182]

Crikey, no need for the sarcasm, people merely expressing their thoughts to try and assist you to improve efficiencies. Makes you wonder why companies set it up like that on install? probably because thats the default setup as done by the manufacturer to cover a wide range of installation configurations and environments and the grease monkeys doing the install dont know any better / havent researched the subject further.
Just as an aside, your first post you state "the energy generated (column 2)" heatpumps dont generate energy, they do as their name suggest, pump heat from one location to another.

No sarcasm intended. Genuinely loving the escalation. I’d have thought it was clear with my post that efficiencies were a focus given I’ve spent nearly a year logging it, but if not, then apologies if I’ve offended you, but if you do have an issue still or in future, just PM me

Makes sense on people just installing and keeping default settings. Just feels totally counter active to the usual reason get ASHP’s. I still feel like there’s massive opportunity within the market for a company to really and truly provide design install and guidance. I found that every company I dealt with I knew more than they did barring the actual installing it part but everybody was parroting the same stock info.

What is the ASHP doing if it isn’t generating energy? I thought its purpose was to transfer heat (energy) from the atmosphere in an efficient way to create additional heat (energy)? Ie mine is generating a ration of 1:2.5 kWh. Or am I understanding it/using wrong terms?

 

[Tomr182]

Originally it was old fashioned aircon systems that used to have water cooling towers exposed to the air that caused most problems. Since then it seems to have extended to any 'stale water' situation. The school I do jobs for run all the taps after holidays, before the kids return, and if away from home for an extended holiday, I tend to run taps, flush toilets etc to get clean fresh water back in the system. I'm not convinced I really need to do that, but water companies are increasingly using UV to treat water rather than chlorine, so you have to wonder how long water will remain potable? Article below is interesting.

https://mytapscore.com/blogs/tips-for-taps/stagnant-water-in-a-vacant-building

I do exactly the same. Having worked in industry it’s covered everywhere. I did ACOP L8 a couple of years ago but quite generic and focused on the typical open water tanks sat stagnant for ever and dead legs. Did talk temperature but was geared to a factory rather than a domestic heating system
I’ll check out the link later on

 

[johnb2713]

I tend to run taps, flush toilets etc to get clean fresh water back in the system.

And where has that cold water been for the last 'x' weeks? it's been sat in the miles of pipework. Running your taps and flushing the loo wont bring fresh water from the reservoir, merely move the water along the pipes surely?

 

[johnb2713]

No sarcasm intended. Genuinely loving the escalation. I’d have thought it was clear with my post that efficiencies were a focus given I’ve spent nearly a year logging it, but if not, then apologies if I’ve offended you, but if you do have an issue still or in future, just PM me

In which case i apologise, it seemed like a ridicule type comment, usual thing I suppose, if something can be read two ways, it was the other way intended

What is the ASHP doing if it isn’t generating energy? I thought its purpose was to transfer heat (energy) from the atmosphere in an efficient way to create additional heat (energy)? Ie mine is generating a ration of 1:2.5 kWh. Or am I understanding it/using wrong terms

Probably wrong terms, it really is just a pump low grade heat from a lot of air and transferring it as high grade heat to a small amount of air. In my humble opinion of course.

 

[binky]

And where has that cold water been for the last 'x' weeks? it's been sat in the miles of pipework. Running your taps and flushing the loo wont bring fresh water from the reservoir, merely move the water along the pipes surely?

I live in a terrace, so neighbours will have been keeping water moving in the road. It's just a case of removing stagnant water from my own pipes basically.

 

[Geoff1946]

"And where has that cold water been for the last 'x' weeks? it's been sat in the miles of pipework. Running your taps and flushing the loo wont bring fresh water from the reservoir, merely move the water along the pipes surely?"

As I understand it the bacteria can only breed in a fairly limited temperature band. Our supply network in UK is supposed to be far enough underground to be too cool for the bacteria to develop. Hence my earlier comparison with overseas practices where exposed pipes are often seen.
When I worked in a legionella controlled place, (a care home), we regularly tested supply temperature and it was supposed to be below a certain level. (low teens C if I recall). And yes, any unused taps had to be run regularly, dead legs removed, etc.

 

[johnb2713]

"And where has that cold water been for the last 'x' weeks? it's been sat in the miles of pipework. Running your taps and flushing the loo wont bring fresh water from the reservoir, merely move the water along the pipes surely?"

As I understand it the bacteria can only breed in a fairly limited temperature band. Our supply network in UK is supposed to be far enough underground to be too cool for the bacteria to develop. Hence my earlier comparison with overseas practices where exposed pipes are often seen.
When I worked in a legionella controlled place, (a care home), we regularly tested supply temperature and it was supposed to be below a certain level. (low teens C if I recall). And yes, any unused taps had to be run regularly, dead legs removed, etc.

I'm just having difficulty getting my head around how water in a sealed pipe that went into the system 'pure' can deteriorate in the absence of light and air.

 

[ProDave]

I'm just having difficulty getting my head around how water in a sealed pipe that went into the system 'pure' can deteriorate in the absence of light and air.

In a modern copper or plastic pipe, I don't think it can. Hence why I don't bother with a legionairs cycle on my hot water.

However a previous house I owned, the incoming water pipe was steel, not even galvanised steel. If you went away for a week, the first water out of the tap was brown with rust. I used to make a habit of run the kitchen tap for a short while each morning before drawing any drinking water, and much longer after we had been away for any time.

 

[Geoff1946]

I don't understand the science behind it either but I've assumed that minor traces of the bacteria can survive the water treatment, but will only become hazardous if allowed to multiply. I think the pre-existing health of potential victims is also a factor, hence the particular care taken when vulnerable people are around.
I tend to agree that healthy people in a domestic environment are unlikely to fall ill.
A perhaps cynical view is that commercial companies engaged in training, water testing, provision of plumbing services, etc are never going to talk it down are they?

 

[rjp44]

I'm just having difficulty getting my head around how water in a sealed pipe that went into the system 'pure' can deteriorate in the absence of light and air.

I think the theory is that Legionella are omnipresent, but don't really grow well enough to present a danger in most conditions, and actually need to be breathed, in large numbers, in a aerosol to cause issues to humans who are not their intended host.
Anywhere there is a biofilm (scum, aquatic slime on the side of a vessel), there are Legionella in large numbers and they multiply best in amoeba in the range 20-40C. Like a lot of nasty bacteria, they can encystify into a very inert, resistant form when conditions aren't right, then move back into a form where they can rapidly multiply when they find the right medium.
Disinfected tap water apparently contains cysts at a very low rate (about 1 per litre), but if they find a warm biofilm with lots of nice stuff to feed on they can colonise the amoeba in it and multiply in huge numbers . The biofilm also protects them from the biocides like chlorine. Some of them then fall off in any water flow and if this then becomes an aerosol which finds its way deep into the lower airway then they accidentally multiply causing severe, quite often fatal, disease in vulnerable people.

 

[Steviesparkie]

I don't understand the science behind it either but I've assumed that minor traces of the bacteria can survive the water treatment, but will only become hazardous if allowed to multiply. I think the pre-existing health of potential victims is also a factor, hence the particular care taken when vulnerable people are around.
I tend to agree that healthy people in a domestic environment are unlikely to fall ill.
A perhaps cynical view is that commercial companies engaged in training, water testing, provision of plumbing services, etc are never going to talk it down are they?

Iirc the bacteria conot multiply under 20 deg c but only temp above 60 will kill it.