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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorneelpeel
    • CommentTimeMar 24th 2022 edited
    I'm considering a single room Air-Air Heat Pump for my soon(ish) to be extended living space.
    Space to heat will be 90m^2 total and about 210m^3 volume once extended.
    The ASHP will be supplemental heat to reduce the use of our oil burner and wood burner as much as possible.
    I'm in Aberdeenshire, so temps often hover around 0 - 5degC in deep winter, but anything near freezing and I would be expecting to put the wood burner on anyway.

    Which Air-Air Heat Pump brands/models should I be looking at?
    How noisy are the pumps? Are they suitable for a living space?
    What is the life expectancy of the latest pumps? (I often hear disaster stories about multi-room ASHPs going wrong and no available bits to fix)
    Any experiences (good or bad) to share?

    Looking at one model as an example - Daikin Perfera FTXM20R
    Nominal heating = 2.5kW (does this mean 7.5kW equivalent at a COP of 3?)
    Seasonal Efficiency SCOP = 5.10 (how this equate to a COP at 0 degC, 5degC, 10degC??)
    Are manufacturers not obliged to show charts of COP vs temperature?
    • CommentAuthorowlman
    • CommentTimeMar 24th 2022
    Most of the big brands; Daikin, Toshiba, Mitsubishi, Panasonic; have similar spec models, and are all reliable.
    I have Toshiba, and I have no worries with outdoor temps, I don't even think about it. Mine's a bigger unit than you are thinking of and it's ducted, but it copes with 200M3 open plan with no problems. If I leave doors open warmth seeps into other areas too. Occasional Summer cooling is a boon.
    Choose an outdoor unit that modulates as demand waxes and wanes.
    Mine's been in 3.5 years and so far it's been faultless.
    Choose a decent "F" gas fitter, not some quick fit turkeys who'll do a budget job, but may omit some of the necessary refrigerant line pressure tests.
    Choose a fitter who'll make a good job of the exterior pipework from both the insulation and the aesthetic perspectives.
    I'd take the power feed back the the CU on its own breaker.
    When you discover how good A/A is you'll most likely want more, - be prepared.
    • CommentAuthorneelpeel
    • CommentTimeMar 24th 2022
    Posted By: owlman
    I have Toshiba, and I have no worries with outdoor temps, I don't even think about it. Mine's a bigger unit than you are thinking of and it's ducted, but it copes with 200M3 open plan with no problems.

    Interesting. What model do you have? And do you have an idea of the average COP and COP at different temps (achieved as opposed to advertised)?
    Unfortunately the summer cooling function will not be well used up here. :-)

    I've also read elsewhere about de-icing cycles and how they impact the COP. Is this on A/A or just A/W do you know?
    • CommentAuthorEd Davies
    • CommentTimeMar 24th 2022
    Posted By: neelpeelNominal heating = 2.5kW (does this mean 7.5kW equivalent at a COP of 3?)
    Usually the numbers quoted are the actual heating/cooling capabilities for some nominal conditions.


    says maximum current 8.93. Assuming that's amps at 230 V then that's a maximum power of a tiny amount over 2 kW, and that'll be for startup or defrost or whatever, so we can further, but safely, assume the normal running consumption will be less which confirms that the quoted power is for heating and the likely normal electrical consumption will of the order of 800 W.
    • CommentAuthorowlman
    • CommentTimeMar 25th 2022 edited
    Hi Neil,
    These are the Toshiba model numbers I have:-

    1. R32 Outdoor unit..... RAV GP 801AT-E


    2.Indoor Unit..... RAV RM80 1 BTPE


    3. Controller..... RBC-AMS54EES


    As I said though, this is a ducted system, not what you are looking for.
    • CommentAuthorTimSmall
    • CommentTimeMar 25th 2022
    I've previously come across this one:


    Electrical power usage in heating mode on that model is listed as:

    min 170 W, nominal 650 W, max 1020 W.

    Heat output is:

    min 700 W, nominal 2700 W, max 3600 W.

    I'd guess 1020 is defrost, and if so that's a 4:1 modulation turn-down. It lists the design power output at -10°C as 1900 W. SCOP is 4.6. That's the smallest in the range, largest is 8.6 kW nominal heating capacity (sold as 7.1 kW which is the cooling capacity).

    ... I think a few manufacturers are planning on introducing R290 mini-splits (slightly higher efficiency, and much lower GWP, but more flammable - that having been said, I don't think the risk is as high as having e.g. a gas boiler or hob), so I was planning on waiting for one of those.

    Midea are supposedly planning to launch one in the EU + UK (they already supply elsewhere I believe), and are reasonably well regarded amongst the Chinese brands (they are a Toshiba manufacturing partner I think).
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