Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: M on April 08, 2017, 06:29:48 PM



Title: Small ASHP (Split system) Install
Post by: M on April 08, 2017, 06:29:48 PM
Hiya. Thought I'd start a thread on this, as i finally got a small (3.5kW) ASHP (air con unit) installed, after 4 years of pondering. I actually raised some thoughts questions on this thread in July 2013 (http://www.navitron.org.uk/forum/index.php/topic,20513.0.html).

Apologies if all of this is obvious to everyone, or most folk, but I thought it was worth a mention, and also so others could correct or amend, or just polish, some of my ideas and conclusions.

OK, here we go. We have GCH which works well, I don't think we use 'too' much as annual gas consumption is about 7-8,000kWh and that includes hot water and gas oven (hob is induction).

During the 'shoulder months' Feb-Apr & Sept-Nov we often use a 400W oil rad to keep the chill off the living room during the daytime, between morning and evening gas burns, or on the warmer, but not quite warm days to help warm the living room up. Often it's not enough.

The thought occurred to me that getting a COP of perhaps 4+ from that 400W would be a good thing, so I started pondering small split system A/C units. I also started to chat on the MSE website, and one guy on their ran with it, started a discussion thread, and later got a unit installed. Another South Walian also did the same at the end of last year. Following their success, pleasure and enthusiasm, I finally took the leap on April Fools Day.

Some theory:-

Personal economics - If the leccy comes from PV, then until export is metered, it's free (I currently export about 70% of generation). But even if bought, then during the warmer shoulder months when I hope for a COP of 4 or 5, then 1kWh of leccy costs me 12p, v's 2p for 1 kWh of gas. But at 80% efficiency (my boiler is certainly less) 6kWh gives you 4.8kWh of heat, so comparable to the leccy ASHP on price.

But, because I'm only maintaining heat in a couple of rooms, and not heating the whole house (which would mean extra heat loss) then gas consumption will be far less. the other S. Walian, who does have much higher gas consumption than myself, reported these figures for Feb and Mch 2017 v's 2016:
Feb gas consumption down 1,489kWh, leccy import up 64kWh
Mch gas consumption down 882kWh, leccy import up 34kWh

Obviously there could be weather issues, but he checked and thought the years were comparable, and my 1st qtr gas consumptions for the 2 years are very similar.


Environmental issues - It's probably safe to assume that any leccy I fail to export, or any additional leccy I import will be made up by gas generation, so at approx 50% efficiency, the gas plant will burn 2kWh of gas to replace the 1kWh of leccy I used. But the ASHP COP should be 2+, so that should make up for it, plus the greater savings again, from localised heating, rather than a full GCH burn.

The noise from the indoor unit is impossible to hear, though the fan can be heard as you dial up the speed, and I'd probably use the fan most of the time to blow the air through the living room, and out into the hall if warm enough, using the door as a control. The outside unit is also very quiet, and can't be heard from about 10m, so much less noise than I expected, however I did go for an LG model which claims to be very, very quiet.


Costs - I did consider the DIY units, but was too scared in the end, but fully installed, including some additional costs for going through 2 walls, plus a case of lager because the guys were so helpful from the very start, and initial phone contact, it all came to 1,100.


Not sure if it'll ever make the 1,100 back in savings, but hopefully I'll be able to report back some gas savings, which will mean a reduced carbon footprint. Plus the air con part may be highly valued on those rare occasions when the house can't cool down overnight, such as about 1 week in 2015, and 1 day in 2016.

Longer term, when batts become viable, I'd hope to be able to make use of the ASHP, with even less import, during times when generation is fluctuating up and down (above and below demand.)

Lastly, it was installed on 1-4-17, the first truly warm day of the year here, and it's been warm ever since, so apart from having a play with it, and testing it out, I timed it perfectly to be of little to no use till Sept+ ........ oh well. Some April's seem to need lots of heating throughout, and some need next to no heating, this one has actually required the early 'cracking' of windows (locked but slightly open?) to get rid of the heat / solar gain.


Title: Re: Small ASHP (Split system) Install
Post by: GarethC on April 11, 2017, 09:34:01 AM
Very interested to hear how you get on. The recent large reductions of grid emissions intensity underpin what you say about only needing modest COPs to achieve lower emissions than GCH.

Unlike even 3-4 years ago, probably means that heat pumps are now a much greener option than GCH even if they provide hot water relatively inefficiently.


Title: Re: Small ASHP (Split system) Install
Post by: pdf27 on April 11, 2017, 11:32:15 AM
Average emissions are slightly misleading - what counts is the marginal emissions, i.e. what power station is fired up to meet the additional load on the grid. The virtual extinction of Coal is very good news here though - this summer for instance the national grid are predicting that the marginal plant will all be gas rather than coal, but not by very much: they're predicting electricity prices to be at a level where all the gas plants would make a small profit on running and all the coal plants would make a slight loss. Increase demand somewhat (by adding heat pumps, making it winter-time, etc.) and I think the marginal plant would probably be coal rather than gas.

Combined cycle gas turbines are in the region of 50% efficient, so for all seasons except winter it looks to me like a heat pump with any COP above 2 would be the best option right now. For winter use I'm not so sure - as you need to assume that the marginal load will come from coal for a big chunk of the time and gas the rest the required COP to be better will go up significantly. I **THINK** this means that for well insulated houses heat pumps are probably the best option, and for badly insulated ones gas probably is: that also fits with the economics (big heat pumps are expensive, small gas users get hammered by the standing charges).


Title: Re: Small ASHP (Split system) Install
Post by: M on April 11, 2017, 12:39:35 PM
Hi guys, that seems to fit with my reasoning, and the use of a secondary heat source for selected use. I based all my grid impact thoughts on gas gen as that will be the marginal source ramped up (theoretically) to meet my increased leccy demand, or to cover my reduced PV export.

The big lightbulb moment though, and I agree that this will also be outside of the coldest days/months, is the large reduction in whole house GCH from targeted heating, as experienced by the other MSE poster and the large gas savings - they are not direct savings of less gas v's more HP, but rather avoided gas consumption from allowing most of the house to cool down more than normal, and thereby reduce heat loss (reduced heat differential).

I'm not sure about the efficacy of running the HP and GCH at the same time, to use spare PV generation. I'd never do it with the oil rad, but perhaps the HP COP makes up for it. My assumption here is that if there's spare generation, then there's probably semi-decent sun, and whilst cold outside still warmer than nighttime when COP will be lower.

I don't know if duplicating heating capital costs, and an extra 1k spend can be justified, but I suspect at worst it won't be too bad. I'll need to see what impact it has on both leccy and gas consumption (and comfort) then try to rationalise all of it at some point in the future. That'll be fun!


Title: Re: Small ASHP (Split system) Install
Post by: pdf27 on April 11, 2017, 02:09:21 PM
The big lightbulb moment though, and I agree that this will also be outside of the coldest days/months, is the large reduction in whole house GCH from targeted heating, as experienced by the other MSE poster and the large gas savings - they are not direct savings of less gas v's more HP, but rather avoided gas consumption from allowing most of the house to cool down more than normal, and thereby reduce heat loss (reduced heat differential).

I'm not sure about the efficacy of running the HP and GCH at the same time, to use spare PV generation. I'd never do it with the oil rad, but perhaps the HP COP makes up for it. My assumption here is that if there's spare generation, then there's probably semi-decent sun, and whilst cold outside still warmer than nighttime when COP will be lower.
Actually, I'm not sure how much is from targeted heating and how much is from the fact that boiler efficiency will suffer (possibly quite badly) when working at a small fraction of capacity and short-cycling. I've certainly seen data from the US where oil fired heating used for hot water in summer was horrifically inefficient because it was operating at a small fraction of design load - gas fired boilers should be significantly better, but I still suspect the efficiency will be pretty poor.


Title: Re: Small ASHP (Split system) Install
Post by: GarethC on April 12, 2017, 10:07:51 AM
Good points pdf.

One thing though, if we all switched from GCH to heat pumps, net we would consume less gas overall.

That's if the gas previously used for heating was instead used to produce leccy in 50% efficient power stations (and used to power heat pumps) AND the heat pumps averaged COPs of greater than two.

If on average they achieved 2.5 (which I think is realistic to conservative), all other things being equal gas consumption would be 20% less.

Of course, if uk demand for gas for GCH declined by 20% (which would be a hell of a lot if you think about it), it should reduce the price of gas. And cheaper gas would increase the chance the gas met marginal increases in electricity demand instead of coal.

Does that all scan??


Title: Re: Small ASHP (Split system) Install
Post by: M on April 12, 2017, 10:19:28 AM
Actually, I'm not sure how much is from targeted heating and how much is from the fact that boiler efficiency will suffer (possibly quite badly) when working at a small fraction of capacity and short-cycling.

Good point.

Messy question, but where full HP heating and super insulating may be hard to promote, do you think developers promoting new builds could successfully market a property with dual heating such as a slightly undersized GCH, with a 1 or 2 room heating/cooling boost given the extra cost isn't massive?

Would folk understand the principle / tricks and benefit, or would it be a pointless diversion away from the doing the job 'properly'?


Title: Re: Small ASHP (Split system) Install
Post by: M on April 12, 2017, 10:25:30 AM

Does that all scan??

Interesting. I'm trying to find an annual average COP for ASHP in the UK, but they do seem to vary from site to site. I think estimates are 2.5+ with a few suggesting 2.9-3.5, so that would seem to support your figures. Location is presumably important too, say a southerly heat sink city, v's rural Scotland.

I'm obviously looking at the better end as I'm avoiding nighttimes, and the very coldest daytimes in mid winter when GCH will almost certainly be needed to maintain temps, so my average should shift upwards by 'cherry picking' usage.


Title: Re: Small ASHP (Split system) Install
Post by: GarethC on April 12, 2017, 10:31:01 AM
Frankly, for a small, modern split system used for heating only not hot water I'd be amazed if you didn't manage a COP of 3+ even if you didn't cherry pick. It's the hot water element that bashes the COP below that.

There's a decent government report with the best data, but these are for systems including hot water (and even they had a median of about 2.5). I'll try to find it if I have time. I've got data from a Swedish government agency which showed that modern air conditiomers actually managed nearer 4 in a much colder country.


Title: Re: Small ASHP (Split system) Install
Post by: GarethC on April 12, 2017, 10:50:48 AM
https://www.gov.uk/government/publications/detailed-analysis-of-data-from-heat-pumps-installed-via-the-renewable-heat-premium-payment-scheme-rhpp

A new one hot off the press! Haven't looked in detail, but I - think- it suggests you should get at least 2.75 (mean of their results) since it's not doing hot water.

The overall mean for systems inc hot water was 2.65. Not too shabby. With new r32 systems (only recently available and about 7% better than the previous r410a iirc), 3 should be realistic. These things are now a pretty good way to cut emissions.


Title: Re: Small ASHP (Split system) Install
Post by: Fionn on April 12, 2017, 12:09:05 PM
I'm looking at putting in one of these myself for a home office where it doesn't make sense to run the gas boiler to heat one room.
Another benefit is that it's nice to have an alternative relatively inexpensive heat source available should your boiler pack in at short notice.
A separate CO2 based heatpump (COP of 4 approx) for hot water is probably the best option if one didn't have PV diversion or solar thermal available.


Title: Re: Small ASHP (Split system) Install
Post by: M on April 12, 2017, 12:41:50 PM
These things are now a pretty good way to cut emissions.

Also hot of the press, had some totals for 'the other guy' in S. Wales who had the install last November, and I'm truly staggered.

Jan to Mch 2016 gas consumption was 6,423kWh
Jan to Mch 2017 gas consumption was 2,804kWh

[ For comparison and to hopefully exclude weather differences, I'm about 20 miles away and my consumption for the 1st quarters was
2016 352 units approx 3,900kWh
2017 357 units approx 4,000kWh ]

Extra leccy import comes to 124kWh, and a total guess at diverting another 124kWh of PV leccy, makes it 248kWh of leccy, and about 500kWh of gas burnt for leccy generation.

I knew the theory here, but have to admit to being shocked.


Title: Re: Small ASHP (Split system) Install
Post by: pdf27 on April 12, 2017, 01:15:03 PM
Messy question, but where full HP heating and super insulating may be hard to promote, do you think developers promoting new builds could successfully market a property with dual heating such as a slightly undersized GCH, with a 1 or 2 room heating/cooling boost given the extra cost isn't massive?

Would folk understand the principle / tricks and benefit, or would it be a pointless diversion away from the doing the job 'properly'?
I think that's an awful lot of money and complexity for not much benefit - far better to force them to go for heat pump heating and proper insulation via the building regulations instead.


Title: Re: Small ASHP (Split system) Install
Post by: Countrypaul on April 12, 2017, 03:58:20 PM
Messy question, but where full HP heating and super insulating may be hard to promote, do you think developers promoting new builds could successfully market a property with dual heating such as a slightly undersized GCH, with a 1 or 2 room heating/cooling boost given the extra cost isn't massive?

Would folk understand the principle / tricks and benefit, or would it be a pointless diversion away from the doing the job 'properly'?

Given that many people don't appear to see the benefit of running the GCH at a lower temperature for longer to promote the condensing mode - and I am told that many plumbers installing GCH set the boiler for >60 routinely, I suspect having 2 systems in place to warm a house is likely to result in both running suboptimally and consequent higher total costs.  facepalm Maybe I'm too cynical, but I strongly suspect there is a huge difference between those on a forum like this and the majority wth GCH that just see a thermostat to allow their lounge to be 25C within half an hour with no idea on how to reduce the amoun of gas they use.

I agree with pdf, force builders to build better homes with heat pumps, probably mvhr systems, integrated PV and lots of insulation properly installed.


Title: Re: Small ASHP (Split system) Install
Post by: GarethC on April 12, 2017, 04:51:57 PM
The problem though is the millions of badly insulated existing homes...

In terms of whether a heat pump is better than a gas boiler or not, why should the level of insulation matter? Not sure I follow.


Title: Re: Small ASHP (Split system) Install
Post by: M on April 12, 2017, 05:50:26 PM
The problem though is the millions of badly insulated existing homes...

In terms of whether a heat pump is better than a gas boiler or not, why should the level of insulation matter? Not sure I follow.

I think it's a game of two halves. Countrypaul and pdf are almost certainly right that for a new build I'm over thinking it, and good insulation is the key.

For older houses like mine, I'm pretty convinced now that the use of a HP as a secondary targeted heat source should be a positive move regardless of the house condition (as you say), though improving insulation where possible is always an important first step.

Hopefully April 2017 to Apr 2018 will be comparable to 16/17 and I'll be able to report some interesting gas consumption figures next year.


Title: Re: Small ASHP (Split system) Install
Post by: pdf27 on April 12, 2017, 05:51:56 PM
In terms of whether a heat pump is better than a gas boiler or not, why should the level of insulation matter? Not sure I follow.
Two reasons:
  • Heat pumps only really show significant gains if you run them at low temperature - with a badly insulated house it's probably impossible to run the temperature low enough to provide adequate comfort, so you'll end up with them performing no better than a gas boiler.
  • The load on the grid is significant - unless we insulate at the same time as fitting heat pumps, you'll need to spend megabucks on strengthening the grid and increasing power supply. Insulating to good standards cuts the required grid works down to something sensible.


Title: Re: Small ASHP (Split system) Install
Post by: dhaslam on April 12, 2017, 07:57:01 PM
The main difference between using electricity and fossil fuels is that it can be renewable.  By using a renewable supplier all the money you pay goes into new renewable sources and maintaining existing ones.


Title: Re: Small ASHP (Split system) Install
Post by: GarethC on April 12, 2017, 08:25:32 PM
Thanks pdf, but I'm still struggling!

On point 1, HPs give their rated output and COP (say 15kW and 2.5) at a low flow temp (say 40 degrees?) as you say, but I thought that simply means you have to increase emitter sizes. I. E. if your 15kW GCH was running at 60 degrees, moving to an HP means you'll need to increase your radiator sizes by 50% to transfer the same heat to the house at the same rate. In which case they're equivalent, aren't they? 15kW is 15kW isn't it? I dunno.

On point 2, yes I see the load on the grid would certainly increase, but is drawing 5kW of leccy for a 15kW HP that bad? A lot less than one electric shower draws, and less than a couple of kettles. Sorry for all the questions!


Title: Re: Small ASHP (Split system) Install
Post by: pdf27 on April 12, 2017, 08:58:54 PM
On point 1, HPs give their rated output and COP (say 15kW and 2.5) at a low flow temp (say 40 degrees?) as you say, but I thought that simply means you have to increase emitter sizes. I. E. if your 15kW GCH was running at 60 degrees, moving to an HP means you'll need to increase your radiator sizes by 50% to transfer the same heat to the house at the same rate. In which case they're equivalent, aren't they? 15kW is 15kW isn't it? I dunno.
The problem is that radiators end up being massive at low temperatures (halving the temperature difference means you need the radiators to be rather more than twice the size). Even underfloor heating starts to have problems at low temperatures and high heat demand, which is in any case very disruptive to fit.
Insulation solves both the problems - improving things to say the EnerPHit standard takes the peak demand from a few hundred W/m2 down to 25 W/m2, meaning that a (small) standard radiator can still heat it at low temperatures.
Edit: note also that heat pump performance starts to crash above 35C - gas boilers typically operate at 60-80C, meaning a temperature difference of 15 .vs. 40-60C, so it's more like 4:1 than 2:1.

On point 2, yes I see the load on the grid would certainly increase, but is drawing 5kW of leccy for a 15kW HP that bad? A lot less than one electric shower draws, and less than a couple of kettles. Sorry for all the questions!
The problem isn't individual demand, it's everybody for extended periods of time. There are what, 20 million households in the UK? 20 million x 5kW is 100 GW - approximately twice the current UK peak demand - on top of the existing demand which is already happening in winter evenings anyway. It isn't just a matter of building more power stations either - the transmission infrastructure is sized to provide 50GW, and simply won't cope with having to provide 150GW instead. That means the only option is to massively increase insulation levels and switch to some sort of smart grid in order to keep a lid on peak demand.


Title: Re: Small ASHP (Split system) Install
Post by: marshman on April 12, 2017, 10:12:16 PM
Interesting discussion, a few points/considerations I would like to add for furtehr comment/discussion :).

1. A 15kW output heatpump is quite a big heatpump in domestic terms. My ground source one is 10kW output and that heats a very large detached house easily, but the house is very well insulated.

2. As pdf says the COP does "crash" at higher (above 35 deg C) temepratures.

3. The volume house builders are notoriously conservative and anything other than night storage heaters or oil/gas boilers and radiators and the bare minimum of insulation are all they will consider.

4. The general public need educating. They just don't get energy consumption or the concept of saving energy, be it lighting, heating or cooking. You can start with your "it's cold outside so I need to turn up the thermostat" type person, to the its too hot in here I'll open a window. They won't consider insulation, there's no point - they can't show it off to their neighbours - a shiny new car is more important, or the huge Smeg fridge, 50" T.V. etc.

5. Even if you could persuade the general populus to insulate you would then hit the next problem - ventilation, or understanding it. The number of people I know that will spend pounds and pounds on mould removers for their bathrooms, kitchens and even bedrooms. When you say to them open a window to get some ventilation after a bath or shower or cooking they look at you and say but its cold. You explain it doesn't take long to get rid of the moist air and the house will feel warmer after and they think you are mad. They then go on to tell you the dry all their washing indoors. Some people hgave no choice, I accept that, but a lot just don't get it.

6. The government needs to change its approach and a) educate the masses b) change the building regs to up insulation, sort ventilation - preferably MHRV, and ensure wet heating can run at lower temperatures allowing for heatpumps to be used. c) reintroduce the Green Deal or what ever offering cut priced insulation like they did a few years back, but put in some extra money to ensure it is done properly. Even some allowance for double glazing for those in houses with single glazing that can't afford it. Also look at ways of a getting  proper EPC for houses that identifies "easy" wins for the occupier and has some sort of inducement to do them. (carrot or stick could be used).

7.  To be honest I don't think ASHP are a viable option on crowded housing estates - the external unit fans are too noisy.

8. Enticing any sort of retrofit option for heatpumps will be a disaster - cowboy firms will jump on the band wagon of the latest government backed scheme and con people into paying a fortune for inadequate, poorly designed systems that will never work. There are already plenty of examples of that - undersized ground loops being a common problem.

9. I think the PDF fag packet calculation of 20 million households x 15kW is way too high - I know it was just an illustration of the electricity distribution problem but a proportion are electric heating anyway as they are not on the gas grid. The 15kW is not continuous. My last property, a large detached bungalow only had a 14kW boiler. Many smaller terraced places have much smaller boilers. If the government were serious they could legislate to install a proper smart grid,  proper smartmeters and heating systems where turn on was staggered and controlled to limit and manage demand. If houses had enough insulation and thermal mass you could even use it to smooth out the peaks and troughs, effectively storing energy as heat in peoples houses.

At the end of the day I think a combined system would just be too complex for the majority and the expense could/would not be justified.

Roger


Title: Re: Small ASHP (Split system) Install
Post by: Countrypaul on April 12, 2017, 11:51:10 PM
Edit: note also that heat pump performance starts to crash above 35C - gas boilers typically operate at 60-80C, meaning a temperature difference of 15 .vs. 40-60C, so it's more like 4:1 than 2:1.

Do you have any reference for that figure of 60-80C by any chance as it what I thought too, but have no hard evidence for it? From what I recall for a condensing boiler to work in condensing mode it should be below 55C. It could be that an education program on how to use a gas boiler cut not only save a lot of gas and therefore reduce CO2 output, but could also save people an awful lot of money. Maybe an option for future gas boilers should be to not allow then to run at a higher temperature than condensing mode will work at stir: more nanny state perhaps, but I think too many people need help as they just don't get it as stated earlier.


Title: Re: Small ASHP (Split system) Install
Post by: marshman on April 13, 2017, 08:59:32 AM
Edit: note also that heat pump performance starts to crash above 35C - gas boilers typically operate at 60-80C, meaning a temperature difference of 15 .vs. 40-60C, so it's more like 4:1 than 2:1.

Do you have any reference for that figure of 60-80C by any chance as it what I thought too, but have no hard evidence for it? From what I recall for a condensing boiler to work in condensing mode it should be below 55C. It could be that an education program on how to use a gas boiler cut not only save a lot of gas and therefore reduce CO2 output, but could also save people an awful lot of money. Maybe an option for future gas boilers should be to not allow then to run at a higher temperature than condensing mode will work at stir: more nanny state perhaps, but I think too many people need help as they just don't get it as stated earlier.

They operate in condensing mode as long as the return water temp is below 55C. The lower the better. So if you have a 20 dec C temp diff, flow to return, you can in theory have a flow temp of 75 de C and still achieve condensing and hence higher efficiencies. Trouble is, as you say, people can and do turn up the boiler temp and I suspect many so called high efficiency boilers do not run in condensing mode as the temps are too high. Again a problem with education and peoples understanding, or lack of it, about how stuff works.



Title: Re: Small ASHP (Split system) Install
Post by: M on April 13, 2017, 09:50:14 AM
7.  To be honest I don't think ASHP are a viable option on crowded housing estates - the external unit fans are too noisy.
Hiya, just to say this was one of our considerations, and made a bit easier by the fact that it would be in daytime use when 'the world' is a little noisier. However, the outside unit is extremely quiet (as marketed), and when I tested it, by walking down the garden, I couldn't hear it at all at 10m.

I was told they aren't as bad as folk suggest, but it's actually much better still than expected, which the installers promised.


Title: Re: Small ASHP (Split system) Install
Post by: pdf27 on April 13, 2017, 09:56:12 AM
Hiya, just to say this was one of our considerations, and made a bit easier by the fact that it would be in daytime use when 'the world' is a little noisier. However, the outside unit is extremely quiet (as marketed), and when I tested it, by walking down the garden, I couldn't hear it at all at 10m.

I was told they aren't as bad as folk suggest, but it's actually much better still than expected, which the installers promised.
Remember that you've got a small unit running at small temperature differences in temperate weather - exactly the conditions required for minimum noise. Try to get a similar sized unit to provide heating and hot water for the whole house on a cold day and it'll have to work a whole lot harder - not to mention that on modern housing estates you aren't going to be able to get 10m away without being in someone else's living room!


Title: Re: Small ASHP (Split system) Install
Post by: Countrypaul on April 13, 2017, 10:18:59 AM
Surely for a modern(crowded) housing estate the heating beng supplied centrally in a "district" heating system should be one of the considerations rather than the assumption that each place should have its own boiler? Whether this would be a GSHP, ASHP, Gas boiler, Solar thermal, PV, CHP system etc. or more likely a combination should almost be a secondary consideration. However again as stated earlier, this would require the estate developers/builders to be a little more adventurous and think a little bit more, so probably little chance  :(


Title: Re: Small ASHP (Split system) Install
Post by: M on April 13, 2017, 10:43:38 AM
Hiya, just to say this was one of our considerations, and made a bit easier by the fact that it would be in daytime use when 'the world' is a little noisier. However, the outside unit is extremely quiet (as marketed), and when I tested it, by walking down the garden, I couldn't hear it at all at 10m.

I was told they aren't as bad as folk suggest, but it's actually much better still than expected, which the installers promised.
Remember that you've got a small unit running at small temperature differences in temperate weather - exactly the conditions required for minimum noise. Try to get a similar sized unit to provide heating and hot water for the whole house on a cold day and it'll have to work a whole lot harder - not to mention that on modern housing estates you aren't going to be able to get 10m away without being in someone else's living room!

Regarding large units, and less optimal running times, please see thread title and the premise behind it. I suppose for larger units and full heating and hot water noise does need consideration. For us, noise wise, it's very quiet standing right in front of it, far less than quiet conversation and impossible to hear through any windows. The indoor unit is silent, sort of, but you get more noise as you dial up the fan speed.


Title: Re: Small ASHP (Split system) Install
Post by: M on May 01, 2017, 08:28:12 AM
1 month in, and loving it. Didn't expect to get much use in April, especially with the lovely warm start we had, but as the arctic weather came in 'HiPpie' got to do its thing. Probably ran for 100+hrs in April, and the GCH didn't need to come on though the upstairs has gradually cooled down (lost all it's thermal mass) with a week or more of outside temps at between 3-13C ...... so ...... with great regret ...... the GCH has been put back on today to warm the house back through. Hopefully that'll be the last day till Sept, or Oct ..... or Nov  :crossed

Total leccy import for April was 96kWh, last year was 82kWh, and the year before 97kWh, so too tricky to work out how much of HiPpie's work came from import, but certainly looks like the vast bulk was from PV.

Very pleased, and so are the cats, who've moved from the bedroom, and now curl up under HiPpie.


Title: Re: Small ASHP (Split system) Install
Post by: Pressure on May 04, 2017, 12:59:11 PM
Sorry, probably a stupid question, but what is the ASHP feeding? Does it have a radiator or two plugged into it?


Title: Re: Small ASHP (Split system) Install
Post by: Fionn on May 04, 2017, 01:05:11 PM
Sorry, probably a stupid question, but what is the ASHP feeding? Does it have a radiator or two plugged into it?
An indoor fan coil unit, typically wall mounted. It acts as a refrigerant to air heat exchanger and a small built in fan increases the rate of heat exchange achievable with it.


Title: Re: Small ASHP (Split system) Install
Post by: Pressure on May 04, 2017, 01:23:26 PM
So it's basically a fan heater? Or more accurately, an air con unit that also does heating? Cool.


Title: Re: Small ASHP (Split system) Install
Post by: Fionn on May 04, 2017, 02:35:51 PM
Yes, generally all aircon units can heat or cool.


Title: Re: Small ASHP (Split system) Install
Post by: MR GUS on May 04, 2017, 04:21:01 PM
M, ASHP visualisation needed old son 🔬📷

Photos of where any pump "action" are within the property boundary / in relation to neighbours & any "swotty" :hysteria db levels within the immediate area welcome, sighting is a bit fraught with potential for neighbourly disharmony for many considering this tech,  despite it running quieter than that illegally parked diesel engine idling for 15 minutes on the road  banghead: outside of my abode!

In your own time  stir:


Title: Re: Small ASHP (Split system) Install
Post by: M on May 04, 2017, 06:17:30 PM
Hello Gus. Waiting for dodgy video to upload to Dropbox ...... am I allowed to say that?

Hopefully it answers any questions, but some background, I wanted to fit the unit in the living room, but the wall goes through to the kitchen (not conservatory, so it got too complicated. Then I did lots of tests etc on temp difference with conservatory, and Wifey was keen to have the living room/conservatory door open more during the Spring and Autumn colder months.

Conservatory (glamorous name for a normal room with a glass ceiling) isn't too bad, doesn't get too cold, and with a volume of approx 2.4m3 takes next to nothing to heat. Cooling was more of an issue, but new blinds (reflective outer, with a 10mm honeycomb type cross section) seem to keep the heat out. Also, the room is ESE so by around 2pm, when the living room may start to overheat, the sun won't be shining directly on it, so AC will be fighting ambient gain, not solar gain.  still uploading ....

A bonus of using the conservatory is that I've been able to use it on fan only mode, which on full power is louder, as you'd expect a fan to be, and it blows the warm solar gain into the living room. I suspect in full fan mode the noise and 'wind' would be a bit too powerful if overhead.

Outside it's hard to explain, but hopefully you can hear (or not) that it's really not loud at all. You wouldn't have to raise your voice to have a quiet chat right next to it. Video also shows the PV brackets I had made by my friendly neighbourhood iron-man, to form a canopy from 2 of the 5 lower panels.

Hope the vid makes sense (it's done now) but ask away. BTW price was 1,090 plus a case of beer. DIY options are half the price (I paid for install) and the guys said they are good but perhaps slightly less efficient as they come pre-gassed. It can also run as a dehumidifier linking to another thread with clothes drying.

The ASHP is a 3.5kW model, and seems to draw around 600-700W when working hard, so 400W oil rad has been made redundant.

M's ASHP Cool but Hot video (https://www.dropbox.com/s/1um1rggfciiv5i5/MVI_2426.AVI?dl=0)


Title: Re: Small ASHP (Split system) Install
Post by: MR GUS on May 05, 2017, 08:28:22 AM
Cannot get it to work on my kindle currently ... facepalm pah! another day. Cheers M. will resume jealous looks shortly


Title: Re: Small ASHP (Split system) Install
Post by: M on June 20, 2017, 08:14:41 AM
I think the ASHP has already paid for itself with this heatwave. Other than very hot weather we can manage heat by air flow, opening doors and windows and flushing the house through. But this last week has had temps of 30C+ in the East facing garden according to the shaded weather station, right up to 7pm or later.

So HiPpie the heat pump has been keeping the conservatory and living room cool, all run off PV. Last night I turned the temp lower and the fan speed up to make the most of the last generation, then turned it off when generation dropped to about 100W. By the time temps rose again, I was just about able to open up all the doors and windows and start flushing air through again.

Upstairs about 28.5C yesterday evening, hall and kitchen about 26C, living room 22C.

Did not expect to benefit this much, this soon from the A/C, but a massive bonus to the gas saving heat benefits expected Oct onwards.


Title: Re: Small ASHP (Split system) Install
Post by: M on June 30, 2017, 09:04:00 PM
Quick update, but the numbers are small and mostly meaningless for Q2 as will the Q3 numbers I suspect, but, compared to last year I've used 27kWh's more leccy in Q2, which may include some heat pump heating from April, not sure. I assume all cooling during the recent heatwave was from spare PV.

Gas consumption, which is of course highly variable due to weather, was 341kWhs, which was down 202kWh's v's the average of the 3 previous Q2's. That sort of makes sense as I've always guessed that hot water and cooking were around 100kWhs per month, and thanks to HiPpie the GCH stayed off throughout April, and only enjoyed a 30min burn on 1st May.

So far it all looks good, the A/C was a god send, and I suspect gas savings will be noticeable (perhaps 25%?) in Q4 & Q1, but we'll have to see.


Title: Re: Small ASHP (Split system) Install
Post by: MR GUS on July 12, 2017, 10:31:36 AM
YAY, just saw your video,  https://www.dropbox.com/s/1um1rggfciiv5i5/MVI_2426.AVI?dl=0 (on my new low power mini pc) ...thanks M

I think that will go some way with other half as to assistance heating  main room & a bedroom.


Title: Re: Small ASHP (Split system) Install
Post by: mysterons on July 12, 2017, 11:38:27 PM
After watching Mart's video I was convinced too. I'm awaiting delivery of a 3.5kw 12000btu split system and am currently doing some prep (holes through walls, ducting etc) so that it'll be straight forward once I get my hands on the kit.
I've gone for diy as the guys Mart recommended unfortunately don't come over this far. It's quick connect, compressor pre-gassed and the pipework and interior unit already evacuated with a big chunky connector that links the two without the need for a vacuum pump and gauges.
I'll be installing the unit upstairs at the furthest point from the Esse wood burner which although it heats the majority of the house this particular area doesn't benefit so much.
The geriatric lpg boiler developed a leak and was disconnected and not used at all last winter, tbh it was rarely used previously since installing the Esse. There's no mains gas out here so hopefully the split system will keep things comfortable.
Immersion on E7 and solar thermal heat the water so the lpg gasser isn't missed at all.


Title: Re: Small ASHP (Split system) Install
Post by: M on July 13, 2017, 07:28:11 AM
After watching Mart's video I was convinced

 ..... that I should have dusted before I started!  :-[


Title: Re: Small ASHP (Split system) Install
Post by: eabadger on July 13, 2017, 09:49:32 AM
we have a 3500 output inverter split heater, we bought it when in the mobile home whilst building, didnt use it much as we got the wood boiler installed soon after, we then installed it in the new build with intention of quick heat in mornings, but never found the need, but last few weeks it has been brilliant in cooling mode, large open plan area went from 36* down to 24* within maybe an hour.
we had to top gas up in the thing, it cam with pre gassed pipes when new, when we moved it i read on line method to get gas in to one of the split parts, worked well, but after ages of not being used some gas had seeped away, i bought a refill kit from italy and it worked a treat, think it was 39.

i have just installed a monoblock air to water pump, and think i would go with these for heating rather than air, but that may just be me.

steve


Title: Re: Small ASHP (Split system) Install
Post by: M on September 16, 2017, 07:54:21 AM
Just to say that HiPpie has been woken from its slumber. Excellent way to raise the living room temp from slightly chilly to fine. One day the forecast was greyish all day, but PV gen was about 1,000W so I put HiPpie on and left the living room door wide open and it warmed up the house a bit and hopefully the thermal mass of the living room too. Normally in Sept solar gain is enough, but it's been a messy start so far, though the next week is supposed to be better. Regardless, no GCH yet and almost all heating covered by PV.


Title: Re: Small ASHP (Split system) Install
Post by: M on November 19, 2017, 07:57:30 AM
Quick update, but end of December will be more interesting when I can compare gas for the quarter.

HiPpie the heat pump was used quite a bit in October, and leccy import was 152kWh v's 138kWh for 2016 & 144kWh for 2015. But it's been used 'tons' (a technical term) in November. On most of the day, regardless of generation, though I suspect 75% has been PV so far, but this will drop as my E/W PV falls off a cliff in Nov.

I can't say enough how well this works, and effectively turns the thermal mass of the house into a PV battery with the COP making up for the lower value of heat v's leccy.

December and Jan should be interesting, HiPpie will be able to keep the living room warm, but the rest of the house will cool down considerably I expect. So will be interesting to see how often we put the GCH back on (or not) during the day on top of the usual morning and evening burn.


Title: Re: Small ASHP (Split system) Install
Post by: todthedog on November 19, 2017, 08:43:57 AM
Just to add my bit everywhere in Sweden, the preferred make being Mitsubishi, as the most reliable, Swedish equivalent of 'which' mag. Also the most widely installed, me walking around. We used it in the shoulder months switching to a wbs in deep winter .
Ours was air/air. No problems with noise inside or out, even standing next to the outdoor unit at full tilt you could hold a normal conversation. To me at least completely non invasive.


Title: Re: Small ASHP (Split system) Install
Post by: M on February 11, 2018, 06:34:03 PM
Experiment (if I can call it that) is going well. The ASHP is getting far more use than I expected. Dec and Jan saw leccy import increase by about 30kWh each, so annual increase, or 6 month increase to be more accurate is looking like being less than 200kWh.

Will be hard to calculate gas savings as weather will confuse the results (and myself), but 2,000kWh out of 7,000kWh for GCH might be doable, not sure.

Generation is picking up now, and that means I can ramp up the temp and leave the living room door wide open to put more heat into the thermal mass 'battery', whenever generation exceeds demand. So far this month, and most of Jan, we haven't needed to put the heating on between 8am (when it stops) and 4pm (when it restarts).

Based on this I'm now completely re-thinking my future battery plans, which were for about 4kWh of useable storage. I'm now thinking of going big, if costs fall, perhaps by 2020-22, so maybe a 10-15kWh battery. This will allow more use of excess PV for ASHP in the shoulder months, and 'free' motoring for the better 6 months of the year, as spare daily storage should exceed average daily miles if we get an EV.

Also worn Wifey down on the 'oh God, no more PV, please' argument, and she's ok'd 4 panels for the garden, which I intend to mount portrait, south facing at a steep 60d pitch. Just 1.3kWp would add nearly 60% to our miserable December generation, when E/W panels struggle the most.

The plan is very sketchy at the moment, but I'm thinking a simple scaffolding pole frame, with the 4 panels linked into my ESE Solaredge system, so minimal costs, and this will also mean a 5%VAT rate on the battery and install, rather than a 20% rate.

Might be pie in the sky, but if it all works, then import should be cut from 1,500 today (3,000 before PV) down to about 400kWh, but then add on 6 months of EV 'fuel' from E7.

Have to say my ickle ASHP rocks, we love it.


Title: Re: Small ASHP (Split system) Install
Post by: Fionn on February 11, 2018, 08:23:45 PM
Sounds great, have you done much analysis on COP during the colder winter months?


Title: Re: Small ASHP (Split system) Install
Post by: M on February 12, 2018, 07:15:56 AM
Sounds great, have you done much analysis on COP during the colder winter months?

Hi. Simple answer, no.

I haven't noticed any difference, but I suspect that's simply down to whether I have the living room door open a crack (for cats) or wide open. So even if outside temps are 2C or so, the tiny conservatory heats up fast, then maintains temp in the living room fine.

Also, all use is daytime, say from 8.30am to 3.30pm (but starting to widen now with better sunlight), so no fighting with nightime temps.

I'm also using it when generation is too poor, but those days tend to be grey, muggy and a little warmer.

If generation is high, then living room door is wide open, and ASHP temp wacked up to about 24C. Living room sits at about 20C, and loads of heat goes into hallway. Low gen then living room door only cat-cracked and ASHP on 21C, with living room at 20C.

Might sound like a lot of fuss, but it's all been quite natural, and Wifey tick of approval as she says the heat is more natural feeling, and not as stuffy as GCH.


Title: Re: Small ASHP (Split system) Install
Post by: MeatyFool on February 26, 2018, 01:18:58 PM
Mart,

This thread has had my thinking for a while.  Our GCH boiler is over 10 years old now, and chances are we will end up getting it replaced with gas again.  But your ASHP reports have left me thinking I should at least be able to reduce gas consumption and possibly eke out our existing boiler a year or two more.

Where my circumstances differ is that we tend to have the house warmer than "average" and to date have had no secondary source of heat.  Our CH programmer has no "+1" button so invariably in the winter it gets set to "once" so is on from 0530 to 2000 (we do have a room stat).  As an aside, if I set the second and third timings better, we might be able to get 2-3 hours a day with the heating off.  A significant saving in itself (3 hours would be 20% - sheesh, doesn't lethargy cost you!)

If I were to try to run with just the ASHP in the shoulder months, I cannot imagine that the heat will travel too far from the inside unit, thereby making other parts of the house feel colder?  Is this your experience?

Someone else has posted how to build your own +1 button on here.  I would suggest that if my wife and I could be trained to refrain from "once"ing the programmer and choosing "+1" when we notice the house starting to feel colder, we could gain a lot of the gas reductions even without the expense of the ASHP.  Of course that is a factor of insulation, and I would say our house is a combination of good, bad and indifferent in that regard!

Meatyfool..



Title: Re: Small ASHP (Split system) Install
Post by: M on February 26, 2018, 01:53:01 PM
Hiya. It will depend on the weather, and obviously today is rather 'extreme', but the blower in the conservatory (more of a small sun room) is running at about 25C, whilst living room is 20.5C with the door half open, and then the hall is colder, but pleasant. Effectively I use the living room door* as the temp control:

if gen is low, I put the HP to about 21c or 22C, the door is just ajar (for the cats),

if gen is high I put the HP to about 25C and leave the living room door wide open to put as much heat into the house (thermal mass battery?).

*That's the living room to hallway door. The living room to sun room is always wide open when the HP is on, as is a small window to the kitchen.

I suspect that in the shoulder months there would be far too much heat without having internal doors wide open, and might, just might mean no evening GCH burn is needed.

So far this winter I haven't put the heating on during the day, which has really surprised me, but it does mean I can go upstairs and find it's 17C or even less.


Title: Re: Small ASHP (Split system) Install
Post by: MeatyFool on February 26, 2018, 03:01:01 PM
Many thanks.

I suspect that we would rarely operate the ASHP on its own.  We do prefer to have the whole house a uniform temperature.  But there should still be massive carbon/cost savings if it reduces gas consumption.

Just need to work on the spousal factor.  Your SF seems to be positive?

Meatyfool..


Title: Re: Small ASHP (Split system) Install
Post by: Fionn on February 26, 2018, 03:22:20 PM
Meatyfool, you could always install more than one mini split or a multisplit.


Title: Re: Small ASHP (Split system) Install
Post by: M on February 26, 2018, 05:18:59 PM
Meatyfool, you could always install more than one mini split or a multisplit.

You beat me to it.

The last couple of weeks I've had way more watts than I need, and could easily have run another HP too. I don't need to, but I would certainly suggest anyone thinking about to just consider maybe a more 'meaty' unit, perhaps 5kW and a dual split with two units, the second one used for additional property heating when gen is high.

My system is quite big, but I'd expect a 4kWp south facing system to be doing even better at this time of year.

@ Meaty, BTW, if it helps, the lounge was 16.8C when I popped in there today at 2pm, so that's what would have happened in the living room. Upstairs at 5pm (nowish) when the GCH kicked back on, the temp was 16.1C, but to be fair, it's bleeding cold today. But that gives you an idea of what heating I've hopefully avoided and gotten for 'free' (give or take the ,000's I've spent).

Other thoughts, which I may have posted previously, if your boiler does fail, then at least you have a secondary source of heat, and the AC was absolutely priceless last May when we had that crazy heatwave, which would have made me quite ill otherwise.


Title: Re: Small ASHP (Split system) Install
Post by: MeatyFool on February 26, 2018, 06:17:07 PM
Thanks again.

I'm going to have to research this some more.  What I need to get straight is placement.  A split unit in the living/dining room would be great as it backs onto an outer wall that has very little footfall and would be ideal for the outside unit.  if I place another inside unit in rooms further away, that is a lot of pipe work for a multi split.

I can be very easily sold on this!

Meatyfool..


Title: Re: Small ASHP (Split system) Install
Post by: M on February 28, 2018, 10:53:03 AM
I lost!

Have had to put the GCH back on today, first time I think during the day in 2018, the morning burn (5.30am to 7.10am) couldn't compete with the steady loss of thermal mass heat over this last week, and it's blumming cold outside. Also, partly my fault as I reduced the morning and evening burns as temps rose in Feb.

The ASHP is on, and the dial set to '11', with sun-room and living room warm, and door partly open (dog is here at the moment and he's considerably bigger than the cats), but upstairs is just too cold.

Hopefully normality will be restored on Sunday when temps bounce back up.


Title: Re: Small ASHP (Split system) Install
Post by: stannn on February 28, 2018, 11:21:09 AM
You need more dogs Mart, big ones with no fur.
Stan


Title: Re: Small ASHP (Split system) Install
Post by: gnarly on February 28, 2018, 01:19:00 PM
Yes that's my experience with a mini-split in freezing weather too.  Remember these things only put out 2.5 kW or so (and that goes down once you get into frequent defrost cycles) so no way can it heat an entire house.  Also they tend to ice up as the drain gets frozen.  Mine also gets very noisy.
They are great 90% of the time and really save money and co2 but you do need an alternative heat source whether GCH or multiple big dogs!!


Title: Re: Small ASHP (Split system) Install
Post by: M on February 28, 2018, 04:00:06 PM
You need more dogs Mart, big ones with no fur.
Stan

Actually I owe poor Richard an apology, despite being a large fella, he is more than capable of 'slithering' around a mostly closed door, whereas the cats take the view that if the door gap is marginal, then they should shove it full open. Gits!


Title: Re: Small ASHP (Split system) Install
Post by: M on February 28, 2018, 05:55:39 PM
Quick update, leccy import this Feb was 10kWh's more than last year, and 20kWh more than 2016, 10kWh more than 2015. So my hope of importing no more than 200kWh more than before still looks good, as monthly import appears to be less than the +30kWh I guessed at (x 6 months pa).

I don't have monthly gas figures for previous years, only quarterly, but Jan and Feb are a slightly higher than 2/3rds of an average 1st qtr, which seems OK, assuming Mch's are normally warmer, and also my Mch gen is more than Jan + Feb combined, so I'd hope to be able to use the HP more, and from earlier to later, plus a better COP as outside temps rise.

No idea if any of this means much yet, or will ever, but it's an interesting little exercise, and hopefully the info will grow more useful as the years go on.

Edit - just used my Solaredge monitoring to check export, and from that I get a consumption figure (import + generation - export), and that came to 304kWh's with an import of 168kWh (Jan 212kWh). That's my highest consumption figure since I was able to start tracking it last Aug. My consumption in Jan was 288kWh, which makes sense as the HP has been really going great guns this month. So the HP has allowed me to turn the house into a heat battery for some excess generation.


Title: Re: Small ASHP (Split system) Install
Post by: MeatyFool on March 05, 2018, 12:40:58 PM
Mart (and others!),

I would be happy to go with an alternative heating technology just if it had a CO2 benefit but spousal factor has to cover financial outlay as well.

I can't help thinking I'm being a complete lemon here, hopefully somebody can put me straight.

I am buying electric at 12.18p, gas at 2.825p, and let us assume (say) a COP of 3.  So electric consumed 12.18p, gas saved 8.475p.  Negative return. Yes, the boiler isn't 100% efficient, but even at 90% (10 year old condensing gas boiler), the numbers aren't close.

Wikipedia does state "A high COP of a heat pump may not entirely overcome a relatively high cost for electricity compared with the same heating value from natural gas".  So maybe no cause for confusion at all.

I recognise that Mart refers several times to using the PV output, but my PV is in and operational, so I am "already" using that free leccy.  I can't use it several times over!

Yours confused.

Meatyfool..


Title: Re: Small ASHP (Split system) Install
Post by: M on March 05, 2018, 01:09:24 PM
Mart (and others!),

I would be happy to go with an alternative heating technology just if it had a CO2 benefit but spousal factor has to cover financial outlay as well.

I can't help thinking I'm being a complete lemon here, hopefully somebody can put me straight.

I am buying electric at 12.18p, gas at 2.825p, and let us assume (say) a COP of 3.  So electric consumed 12.18p, gas saved 8.475p.  Negative return. Yes, the boiler isn't 100% efficient, but even at 90% (10 year old condensing gas boiler), the numbers aren't close.

Wikipedia does state "A high COP of a heat pump may not entirely overcome a relatively high cost for electricity compared with the same heating value from natural gas".  So maybe no cause for confusion at all.

I recognise that Mart refers several times to using the PV output, but my PV is in and operational, so I am "already" using that free leccy.  I can't use it several times over!

Yours confused.

Meatyfool..

Hiya. I'm not sure it'll ever pay back just on gas savings, so you are probably right there. But it's important to place some value on having a secondary heat source, and some cooling, though that will be very rare.

At a COP of 3, expect to replace 4 units of gas (75% efficient), so 12.18p leccy v's 11.3p.

But, and here's when the numbers become more a leap of faith. Some of that leccy should be PV, I already had the PV, but I was exporting most of this. Today the ASHP went on at 8am and I've been importing little to nothing so far even though it's quite grey as total gen is around 900W.

Next, it's a dishonest comparison. I'm heating the living room (and sun room) with the ASHP, but saving on GCH for the whole house. The more the rest of the house cools, the less heat I lose as the differential between indoor and outdoor temps reduces.

I appreciate that the GCH will have to work harder when it comes back on, but I still save by having less 'all house' heat.

Also, whilst I'm happy to use a COP of 3, since the UK average is apparently 2.9 for an ASHP, do remember that in this case you will be avoiding night time use, and the worst of the winter use, so the average COP is probably better as you pick and choose the best times to use it.


Just to be clear, I'm not sure this is a great idea, it just seems like a good one to try, and a bit of fun, and as you mention, I'm pretty sure CO2 wise I'm doing the right thing as the PV I consume, or leccy I import, will cost the grid 2kWh's of gas (for every 1kWh of leccy), so taking the COP into account, should deliver 3-4kWh's of heat, giving a 2 to 1 benefit .... I think?


Title: Re: Small ASHP (Split system) Install
Post by: MeatyFool on March 05, 2018, 01:37:55 PM
Hiya. I'm not sure it'll ever pay back just on gas savings, so you are probably right there. But it's important to place some value on having a secondary heat source, and some cooling, though that will be very rare.

At a COP of 3, expect to replace 4 units of gas (75% efficient), so 12.18p leccy v's 11.3p.

But, and here's when the numbers become more a leap of faith. Some of that leccy should be PV, I already had the PV, but I was exporting most of this. Today the ASHP went on at 8am and I've been importing little to nothing so far even though it's quite grey as total gen is around 900W.

Next, it's a dishonest comparison. I'm heating the living room (and sun room) with the ASHP, but saving on GCH for the whole house. The more the rest of the house cools, the less heat I lose as the differential between indoor and outdoor temps reduces.

I appreciate that the GCH will have to work harder when it comes back on, but I still save by having less 'all house' heat.

Also, whilst I'm happy to use a COP of 3, since the UK average is apparently 2.9 for an ASHP, do remember that in this case you will be avoiding night time use, and the worst of the winter use, so the average COP is probably better as you pick and choose the best times to use it.


Just to be clear, I'm not sure this is a great idea, it just seems like a good one to try, and a bit of fun, and as you mention, I'm pretty sure CO2 wise I'm doing the right thing as the PV I consume, or leccy I import, will cost the grid 2kWh's of gas (for every 1kWh of leccy), so taking the COP into account, should deliver 3-4kWh's of heat, giving a 2 to 1 benefit .... I think?

Mart,

Many thanks for the response.

I have never had a firm understanding of where and when I export (certainly not logged!).  As the COP is greater than one, it is an absolute truth that in the shoulder months I would do better to stop diverting excess PV to the immersion, I should leave the excess to "run" the ASHP.  I do have monthly logging of immersun diversion, that is all.  So I could guesstimate that further away from "mid winter" I am going to be increasingly using PV over import.

The real winner that I had overlooked was that I should theoretically be able to switch off the whole house GCH a few weeks earlier than normal, and switch it back on again a little later.  Whilst from a CO2 point of view I should leave it running all winter, arguing from a purely financial POV, the ASHP could be off for most of the winter where there wasn't the excess PV to run it.

But yes, it is there as a backup should the gas ever run out!

Food for thought,

Meatyfool..


Title: Re: Small ASHP (Split system) Install
Post by: ASB on March 18, 2018, 09:29:08 AM
These things are now a pretty good way to cut emissions.

Also hot of the press, had some totals for 'the other guy' in S. Wales who had the install last November, and I'm truly staggered.

Jan to Mch 2016 gas consumption was 6,423kWh
Jan to Mch 2017 gas consumption was 2,804kWh

[ For comparison and to hopefully exclude weather differences, I'm about 20 miles away and my consumption for the 1st quarters was
2016 352 units approx 3,900kWh
2017 357 units approx 4,000kWh ]

Extra leccy import comes to 124kWh, and a total guess at diverting another 124kWh of PV leccy, makes it 248kWh of leccy, and about 500kWh of gas burnt for leccy generation.

I knew the theory here, but have to admit to being shocked.

Not sure if I am "the other guy" but just joined this forum following links from M.

But these are our first full year figures for the Air Conditioner/Heat Pump that was installed in November 2016.

As we recorded gas & electric consumption before & after we were able to compare year on year figures for Gas and Electric consumption.

Gas use had reduced by 5,588 kWh. That's an over 50% reduction compared to the previous year.

Electric import had increased by 344 kWh. That is an increase of 18% compared to previous year. But solar PV production had been lower in 2017 compared with 2016. Also, been using a lot of high power tools, cement mixer, etc in the garden last Autumn to extend the patio.

Use of Solar PV generated electric in 2017 had increased from about 40% to just over 48%.

So with our unit rates for electric & gas we saved 166.65 on gas, but spent 37.20 more on electric import. A total saving of 129.45 for the 1st year of having the airconditioner/heat pump.


Title: Re: Small ASHP (Split system) Install
Post by: M on March 18, 2018, 09:33:32 AM

Not sure if I am "the other guy" but just joined this forum following links from M.

Have a great big welcome. Nice to see you on board Savvy.

Yep, I've been singing your praises, and of course the success of the ASHP idea to back up GCH and make use of PV. As batteries go, for the bottom 6 months of the year, putting spare PV into thermal mass at a COP of 3+ seems like a perfect solution.

Have fun on Navitron.

Mart.


Title: Re: Small ASHP (Split system) Install
Post by: ASB on March 18, 2018, 12:12:24 PM

Not sure if I am "the other guy" but just joined this forum following links from M.

Have a great big welcome. Nice to see you on board Savvy.

Yep, I've been singing your praises, and of course the success of the ASHP idea to back up GCH and make use of PV. As batteries go, for the bottom 6 months of the year, putting spare PV into thermal mass at a COP of 3+ seems like a perfect solution.

Have fun on Navitron.

Mart.

Thanks for the welcome Mart. Interesting forum with lots of useful info.


Title: Re: Small ASHP (Split system) Install
Post by: M on April 15, 2018, 08:24:22 AM
I forgot to post an update for the 6 months Oct-Mch, so here we go.

Leccy up 158kWh v's the previous year (and best year).

Gas came out at 624 units, v's the previous 3yrs (working backwards) of 664, 565 & 687.

So allowing for DHW and cooking we used approx 10% less than last year. The interesting bit then is when the weather is taken into account, and ASB (who is reasonably local to me) confirmed that this winter was colder than last, and advised that he used approx 1/3 more gas this year v's last.

So, still early days and assumptions based on weather, but working in kWh's, a rough guide might be +150 to 200kWh of leccy and -2,000 to 2,500kWh of gas. These are import figures, as I will of course have also consumed more PV generation, and reduced my export (with the house acting as a thermal store for the PV generation).

So seems like a success, and the living room / sun room door left open to direct the hot air into the living room is excellent for hanging soggy doggy towels on to dry out after hosing down a mud soaked Labrador now that almost every field is a partial bog.  ;D


Title: Re: Small ASHP (Split system) Install
Post by: Fionn on April 15, 2018, 09:16:17 AM
I would say that's a resounding success.
Here in Ireland I've noted an increase in gas consumption of about 35% this winter vs last on a large building I have the figures for.


Title: Re: Small ASHP (Split system) Install
Post by: M on April 15, 2018, 12:09:57 PM
I would say that's a resounding success.
Here in Ireland I've noted an increase in gas consumption of about 35% this winter vs last on a large building I have the figures for.

Many thanks as I need some comparison data before jumping to any conclusions. I found a FT article suggesting a 1/3 more gas consumption this year than seasonal norms, but I suspect it meant during the 'beast from the east' not necessarily the whole 2017/18 period.

I'm probably being overcautious to compensate for my rose tinted glasses, but don't want to mislead anyone.

Also, by August I will have a years worth of export data too, thanks to SolarEdge upgrade, so it'll be interesting to see what percentage of generation I've exported.


Title: Re: Small ASHP (Split system) Install
Post by: Fionn on April 15, 2018, 11:23:08 PM
It was actually for a year to the end of March that it was up 35% in this case. Here at least it wasn't spectacularly cold at any time but it was noticeably cold pretty much all winter so the number of degree days was well above normal I'd imagine.