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Discussion ... ASHP(Air/Air) with Solar pv ....

edited 30 November -1 at 1:00AM in Green & Ethical MoneySaving
354 replies 120.7K views
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  • zeupaterzeupater Forumite
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    Hi

    Following on from the previous post, the performance curve & figures for a range of T0shiba Air/Air units look like this ... http://toshiba-aircon.co.uk/assets/uploads/product_assets/RAS-B10B13B16N3KVP-E_DSK6_5.pdf ...

    What I find really confusing with the engineering performance figures is that data is given for min, nominal & max capacity & partial loading conditions, but this has little commonality to the controllability available in the relevant user manuals .... http://toshiba-aircon.co.uk/assets/uploads/product_assets/Super%20Daiseikai%20Owners%20Manual.pdf ... which only refer to low/med/high control on fan speeds.

    What we would be looking for is a unit where the power drawn would be limited by manual control, something like limiting low to 250W, medium to 500W and high to 1000W in order to match pv generation with the heat output being directly linked to the COP available at these settings in various temperature conditions .... of course, being able to control this automatically depending on generation would be ideal, but talking directly to Toshiba a couple of years ago I was informed that this wasn't currently possible on their small Air/Air systems.

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • zeupaterzeupater Forumite
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    Martyn1981 wrote: »
    Hiya, 100% spot on what I had in mind. To try to keep the house heat above 18C (ideally 19 to 20C) when temps outside are probably 10C to 15C during the day (PV window).

    Tried to dip a second toe in, not so easy. Just had a chat with a company about 1/2 mile away, really helpful, but when they asked the application and I said 1 or 2 rooms in the house, they said they don't do domestic installs anymore as people's expectations are too high.

    He said I (we?) were pretty spot on, with expectations for a small system, perhaps 4 months questionable/too cold if GCH available, 4 months very suitable, and 4 months no heating needed but AC a nice luxury. But still didn't want to know. Has given me another company details, and waiting for call back from a third, but they did say that they are busy and priority to commercial jobs at the moment - which was pretty honest of them.

    Critically, I need to know what those £400/£500 internet supply only prices turn into, when they look around the house and start sucking air through their teeth!

    Another question, you know we were talking about boiler efficiencies for DHW of around 80%, what would that be for heating as some losses (pipework, boiler) would still be beneficial. So would 90% be a fair figure when comparing gas to leccy? Taking that a step further, if a COP of 3.6 could be achieved, would that mean 1kWh of leccy replacing 4kWhs of gas (4*90%), or am I not understanding this correctly?

    Cheers.

    Mart.
    Hi

    On the subject of installed cost I posted this a while back ...
    zeupater wrote: »
    I agree .... Air-to-air is equally as efficient as Air-to-water and would be installed at a fraction of the cost .. even at the highly inflated UK prices ...

    Whilst on the subject, someone I know has a property in Spain and has recently replaced the Air-to-air heatpumps with more efficient inverter based units and after doing so was sufficiently impressed that he looked into having a couple of the same units installed in his property in the UK. He was, let's say, 'a little more than amazed' when all of the UK installers which quoted gave the same set of reasons for their overinflated prices .... seemingly the UK installers cannot buy units in £(wholesale) as the Spanish installers can supply in €(fully installed) ... ;)

    It unfortunately seems that the meaning of the line "Something is rotten in the state of Denmark" applies to the UK these days ...

    Z
    ... quite apt I believe .... but let's leave the margin aspirations of UK installers aside at the moment, but from past experience I have an idea of what would be charged to install into business premises and would certainly push for a similar supply deal ... ;):)

    Regarding COP ... yes, under ideal (/test) conditions the energy performance should be as per your figures. GCH efficiencies are pretty variable depending on average usage, lengths of pipe run, heat settings, weather etc, but I see no reason to not use a nominal 90% for winter heating using a high efficiency condensing boiler (SEDBUK ... http://www.boilers.org.uk/ ) and something lower for water only heating as a baseline if pipe runs are more than a few metres, after-all, you have to start somewhere !

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • tunneltunnel Forumite
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    zeupater wrote: »
    Hi



    What we would be looking for is a unit where the power drawn would be limited by manual control, something like limiting low to 250W, medium to 500W and high to 1000W in order to match pv generation with the heat output being directly linked to the COP available at these settings in various temperature conditions .... of course, being able to control this automatically depending on generation would be ideal, but talking directly to Toshiba a couple of years ago I was informed that this wasn't currently possible on their small Air/Air systems.

    HTH
    Z

    Maybe soon when HP manufacturers see the advantages of multi power settings will we see this. Guess for now its stick with a Wattson or anything else similar. Would be nice if the Wattson manufacturer(or others) picked up on this and produced a HP with something built in, both for using spare PV generation AND changeable power consumption.
    2 kWp SEbE , 2kWp SSW & 2.5kWp NWbW.....in sunny North Derbyshire
  • Martyn1981Martyn1981 Forumite
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    Martyn1981 wrote: »
    Tried to dip a second toe in, not so easy. Just had a chat with a company about 1/2 mile away, really helpful, but when they asked the application and I said 1 or 2 rooms in the house, they said they don't do domestic installs anymore as people's expectations are too high.

    He said I (we?) were pretty spot on, with expectations for a small system, perhaps 4 months questionable/too cold if GCH available, 4 months very suitable, and 4 months no heating needed but AC a nice luxury. But still didn't want to know. Has given me another company details, and waiting for call back from a third, but they did say that they are busy and priority to commercial jobs at the moment - which was pretty honest of them.

    Hi all. Thought I'd just do a quick update, and bump the thread a little.

    Not much has happened, as I'm waiting for a visit to see how the theory stacks up, once a site visit finds problems with my preferred location(s). However, the company is very busy at the moment doing commercial work.

    The chat I had explained that the prices I (we've) seen of around £450(ish) is actually about right. He said that's the rough cost of kit which is popular for loft conversions.

    Also I said that I've been wondering about 2 rooms, but one compressor (multi units), but the prices look to be more than twice, despite single compressor. Again, he said that's about right, it comes down to manufacturing numbers, and much, much smaller demand. Multi's can go up to 6, apparently. He said usually cheaper just to install 2 separate units.

    So, nothing particularly interesting, just an update as not much has happened so far.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • CardewCardew Forumite
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    Unless I have missed it, nobody has mentioned the noise issue with Air to Air HP.

    It might be worth looking at some American websites on these heaters. They are very common in cheapish motels and trailer homes.

    De-icing units can severely dent the COP figures.
  • spgsc531spgsc531 Forumite
    250 posts
    Cardew wrote: »
    Unless I have missed it, nobody has mentioned the noise issue with Air to Air HP.

    It might be worth looking at some American websites on these heaters. They are very common in cheapish motels and trailer homes.

    De-icing units can severely dent the COP figures.

    What a shock....

    cardew being negative....

    (assistant of a) CEO of an energy company? :D
  • Martyn1981Martyn1981 Forumite
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    Cardew wrote: »
    Unless I have missed it, nobody has mentioned the noise issue with Air to Air HP.

    It might be worth looking at some American websites on these heaters. They are very common in cheapish motels and trailer homes.

    De-icing units can severely dent the COP figures.

    Thanks Cardew.

    So that I can be prepared when I meet 'the man', could you give me some constructive advice on these units:

    During daylight operation Mch/Apr & Sept/Oct how often can I expect the units to ice up? And what COP figures can I realistically expect to see?

    Regarding noise, (and the unit examples given on this thread) how intrusive would 24 to 43 dB(A)'s internal be? And 46 to 54 dB(A)'s external be?

    Thanks.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • CardewCardew Forumite
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    You should scan through this 'sticky' thread.

    http://forums.moneysavingexpert.com/showthread.php?t=1464827

    I wouldn't have thought icing would be a problem 'during daylight operation Mch/Apr & Sept/Oct '

    The Air to Air A/C(and heating) in my apartment in the USA(installed 2003) is very loud but as the external unit is on the roof so doesn't matter. Internally the air is ducted to all rooms so the fan noise is muted.

    The latest technology will probably make the units quieter. You can also research acceptable noise levels, however I am surprised that your proposed units can be as loud as 54db:
    A noise level of 35 to 40dB outside a dwelling is acceptable and a maximum of 45dB should be adhered to in order to prevent disturbance to residents

    Obviously the siting of the external unit, and proximity of neighbours is important.

    Not implying noise is a show-stopper - but needs consideration.
  • Martyn1981Martyn1981 Forumite
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    Cardew wrote: »
    I wouldn't have thought icing would be a problem 'during daylight operation Mch/Apr & Sept/Oct '

    Thanks again. So just going back to your earlier post, if you don't think icing will be a problem during the operation being discussed in this thread, does that also mean that the COP figures won't be severely dented either?

    Cardew wrote: »
    The latest technology will probably make the units quieter. You can also research acceptable noise levels, however I am surprised that your proposed units can be as loud as 54db:

    Those are simply the decibel ranges for the kit mentioned prior to your post. The Toshiba is up to 46/47dB(A)'s and the Eco Air up to 54dB(A)'s, 53 for the maximum I would want.

    Cardew wrote: »
    Obviously the siting of the external unit, and proximity of neighbours is important.

    Not implying noise is a show-stopper - but needs consideration.

    Looking up decibel comparison, the upper outside noise appears to come under the heading 'moderate' comparable to a quiet residential street, but a bit louder than moderate rain. But quieter than "chatting with your girlfriends" (60dB(A)s) - which might be a little controversial.

    The Toshiba would come under 'faint' 40-50, which seems to be described as a quiet office.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • One related option we've looked at and are still toying with is the Genvex MVHR system. The idea here is that you have a MVHR system which has benefits in terms of air replacement in an efficient form (so hot wet air out via a heat exchanger - cool dry air in via the exchanger so comes in warmed rather than cold via trickle vents etc but it then has a small ASHP built in so you can either cool the incoming air in summer (which would also bypass the exchanger to avoid picking up heat) or warm the incoming air in winter.

    Noise with these systems isn't normally a significant problem, however from what we can see so far its probably more expensive than a MVHR system + a ASHP system combined and the controller appears to be thermostat based without the required manual options you'd need to use the HP part well with surplus solar.

    I've seen one in action at the Homebuild place in Swindon and they are surprisingly effective. The sales pitch is that we could dispense with our gas CH but I'd need to do some serious number crunching on the costs and the COP to see if that could be worthwhile if it wasn't solely running on surplus (free) solar.

    Its also the case that these systems aren't easy to retrofit to existing homes as you need to get the air ducting into most if not all rooms. However as a concept (coupling a MVHR system to an ASHP) it seems to have some legs - it needs someone to make a unit which is more designed for supplementary heating coupled to solar than the current offerings from Genvex which seem to be designed as total heating solutions.
    Adventure before Dementia!
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