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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    •  
      CommentAuthordjh
    • CommentTimeMay 18th 2021
     
    Posted By: jms452I imagine you don't even need a single room unit in each room.

    Indeed; I wonder whether I could get by with just one indoor unit.
    •  
      CommentAuthordjh
    • CommentTimeMay 18th 2021 edited
     
    Posted By: fostertomIn a hard to insulate i.e. large heat demand house, this would mean a large external unit - can this be 'quiet' as current A-W domestic units, which can be OK?

    Well since the outdoor unit for an A-W system is the same as that for an A-A system, with the addition of an extra heat exchanger adding its little bit of noise in the A-W case, I'd think so :bigsmile:

    A-A gives CoP of 3 or more, like A-W? And so this gets around the loss of CoP with A-W caused when wet rads require supply water flow at hi temp like 60C? because A-A with several remote indoor units has no need to produce hi-temp output, just sufficient comfort-temp warm air.

    Sounds like this could be quite lo-cost installation, even with several remote indoor units? I can see this cd be done with minimal ducting. Tho radiant heat is preferable to blowing warm air around.

    You're beginning to get the idea :cool:
    • CommentAuthorbhommels
    • CommentTimeMay 18th 2021
     
    Posted By: djh
    Posted By: jms452I imagine you don't even need a single room unit in each room.

    Indeed; I wonder whether I could get by with just one indoor unit.


    So you have a PassivHaus, all designed and engineered to make use of the fact that humans perceive higher thermal comfort when the airspeeds are below a certain threshold, and then you are going to blow warm air around? The end result could well be that the heat demand (and losses) increases due to the reduction in perceived comfort. Sure the COP will make up for that so economically it is fine, but is it what you want?
  1.  
    Posted by FT on the previous page
    Will, it's time I looked at these 'heat pumps with newer refrigerants' which I meant above by sceptical 'suggestions otherwise for particular models' - I'd be grateful if you cd point me at relevant make/model(s).

    Sceptical, yes, as AFAIK maintaining CoP of 3 right thro winter is non-negotiable, both to make elect significantly cheaper than fossil thus justifying the cost, and
    to enable the renewable and CCS/H2 electricity supply to grow faster than demand does
    Several other GBF folks have mentioned the Vailant arotherm plus, SCOP of 3.9 when operating with a flow temperature of 50degC. Is using R290 refrigerant which also has a significantly lower GWP than R410 or R32.

    Mitsubishi do a commercial hot water R744 heatpump claiming COP 3.4 at 65degC flow. Ecocute have done a domestic one in Japan for years but not sure how to get it here.

    I am interested but have no direct experience yet.

    And I don't think column vs steel panel w/ or w/o fins makes anything like enough difference, surely, to bring within range of 'efficient at 50degC'?
    Do the sums, then, don't wait for us to do them for you without access to the site data!

    EG:
    Heat flow out of the radiator = U.A.deltaT
    If the house runs just now with rads at 70degC (so deltaT = +50degC above room temperature) and you increase the effective area of the rads by 40%, then you can reduce the deltaT by 1/140%*, so to +36degC above room temperature -> rads at 56degC.

    Then your new insulation will reduce the needed heat flow by another X% -> rads deltaT can be 1/(1+X)% cooler again -> below 50degC

    Then run the heating 24h/d, instead of for 12-16h/d or whatever currently done -> rads can be Y% cooler again

    Then consider the 90% of the heating season when the weather is cool rather than freezing, so when the rads can be Z% cooler again.


    *Not quite that linear... but you'll do the sums properly yourself!

    A-A means ducted warm air, in a typical non-open-plan Listed Building - not feasible
    wrong again, as just discussed!
    • CommentAuthorjms452
    • CommentTimeMay 19th 2021
     
    Posted By: bhommelsSo you have a PassivHaus, all designed and engineered to make use of the fact that humans perceive higher thermal comfort when the airspeeds are below a certain threshold, and then you are going to blow warm air around? The end result could well be that the heat demand (and losses) increases due to the reduction in perceived comfort. Sure the COP will make up for that so economically it is fine, but is it what you want?


    Not a passivHaus - just a moderate refurb of a small 80m2 house.
    Had a vague plan to run a low power A2A in the day particularly in the shoulder months when it is largely running on PV and save the gas boiler for hot water and really cold winter evenings.

    Challenge was the planing committee keen on the air con unit look.
    •  
      CommentAuthordjh
    • CommentTimeMay 19th 2021 edited
     
    Posted By: WillInAberdeenEcocute have done a domestic one in Japan for years

    Ecocute is just the brand name for all R744 (i.e. CO2) heat pumps. It's not a particular manufacturer.

    edit: https://en.wikipedia.org/wiki/EcoCute
    • CommentAuthorowlman
    • CommentTimeMay 19th 2021 edited
     
    Fostertom 15 hours ago quote
    Thanks - that's an eye-opener, guess I shd have checked first.

    In a hard to insulate i.e. large heat demand house, this would mean a large external unit - can this be 'quiet' as current A-W domestic units, which can be OK?
    A-A gives CoP of 3 or more, like A-W? And so this gets around the loss of CoP with A-W caused when wet rads require supply water flow at hi temp like 60C? because A-A with several remote indoor units has no need to produce hi-temp output, just sufficient comfort-temp warm air.

    Sounds like this could be quite lo-cost installation, even with several remote indoor units? I can see this cd be done with minimal ducting. Tho radiant heat is preferable to blowing warm air around.

    _________________________________________________________________________________________________


    Re Noise: There's no reason why an A-A outside unit should be any noisier than a comparative A-W. Under some conditions I can see then being quieter.

    Re COP: Better to use SCOP when doing comparisons. The seasonally adjusted figures give a better comparative performance. My latest 3.3 kW single room indoor project has an SCOP of 4.7 heating, and is A++ heating, and A+++ cooling. These sorts of figures are fairly commonplace with modern R32 modulating units.

    Re Costs: Figures I've seen for A-W installs can reach well into 5 figures. For A-A installs much of the work is well within the capabilities of a competent DIYer. Problems occur when indoor units require to be sited away from an outside walls, e.g. pipework and cable runs etc., no more so than a standard CH install. Distance from the outside to the indoor units have to be observed, 20-30M is fairly common. There is also the FGas engineers costs to factor in. There are other considerations but not deal breakers IMO.
    "Blowing warm air"- although correct, the phrase does tend to conjure up a negative image, personally I don't use it.

    My research into heat pumps generally led me away from A-W and I don't regret my decision. Each to their own of course and the house design and build are fundamental in deciding one way or the other. Heat pumps are generally seen as one solution to reducing fossil fuel usage, and the direction of travel seems to be concentrated on A-W; e.g. RHI. Personally I think the Government have it wrong, A-A is better suited in most cases.
    •  
      CommentAuthordjh
    • CommentTimeMay 19th 2021
     
    Posted By: jms452
    Posted By: bhommelsSo you have a PassivHaus, all designed and engineered to make use of the fact that humans perceive higher thermal comfort when the airspeeds are below a certain threshold, and then you are going to blow warm air around? The end result could well be that the heat demand (and losses) increases due to the reduction in perceived comfort. Sure the COP will make up for that so economically it is fine, but is it what you want?


    Not a passivHaus - just a moderate refurb of a small 80m2 house.
    Had a vague plan to run a low power A2A in the day particularly in the shoulder months when it is largely running on PV and save the gas boiler for hot water and really cold winter evenings.

    Challenge was the planing committee keen on the air con unit look.

    I suspect Bart was referring to my house :bigsmile:

    I think PH are designed to minimise air speeds in ventilation and around windows more because people are sensitive to cold drafts than because people feel especially warm when there is little air movement. [For the benefit of others, it's important to remember that the supply air from an MVHR is still cooler than the room air, so systems need to avoid e.g. blowing it where people normally sit]

    I normally heat my house by blowing warm air around anyway. I turn the MVHR up and heat the air to 45°C. Admittedly it's usually at night but I can never even feel the heat except in one room with the shortest duct length. I really don't think blowing air around at 21-23°C or so is going to make the place feel uncomfortable.

    Given that the smallest air-air units commonly available are twice the output power of the heater I presently use just overnight, I expect I'll be able to find an operating schedule to work around any problems that do occur. Now I just need to wait until I feel the product development and economic background have reached a sensible sweet spot where I can justify a purchase.
  2.  
    Posted By: djh
    Posted By: WillInAberdeenEcocute have done a domestic one in Japan for years

    Ecocute is just the brand name for all R744 (i.e. CO2) heat pumps. It's not a particular manufacturer.

    edit: https://en.wikipedia.org/wiki/EcoCute


    No, Ecocute is just one brand owned by Denso, who I think are part of Toyota. The technology has been licensed to other brands, Mitsubishi, Stiebel Eltron, etc. who sell it in their own branded products.
    https://www.denso-am.eu/products/life-energy/co2-heat-pump/

    CO2 heatpumps are a particularly good fit for heating DHW, which is not what Tom's client is looking for.
    •  
      CommentAuthordjh
    • CommentTimeMay 19th 2021
     
    Posted By: WillInAberdeen
    Posted By: djh
    Posted By: WillInAberdeenEcocute have done a domestic one in Japan for years

    Ecocute is just the brand name for all R744 (i.e. CO2) heat pumps. It's not a particular manufacturer.

    edit: https://en.wikipedia.org/wiki/EcoCute


    No, Ecocute is just one brand owned by Denso, who I think are part of Toyota. The technology has been licensed to lots of other brands, Mitsubishi, Stiebel Eltron, etc. who sell it in their own branded products.
    https://www.denso-am.eu/products/life-energy/co2-heat-pump/

    We're both wrong. According to the wikipedia article anyway.

    "EcoCute (エコキュート, ekokyūto) is a registered trademark (No. 4575216 - Japan)[23] of Kansai Electric Power Company."

    "In 1993 the Japanese company Denso, in collaboration with Gustav Lorentzen, developed an automobile air conditioner using CO2 as a refrigerant. They demonstrated the invention at the June 1998 International Institute of Refrigeration/Gustav Lorentzen Conference.[4][5][6] After the conference, CRIEPI (Central Research Institute of Electric Power Industry) and TEPCO (The Tokyo Electric Power Company) approached Denso about developing a prototype air conditioner using natural refrigerant materials instead of freon. Together they produced 30 prototype EcoCute units for a year-long experimental installation at locations throughout Japan, from the cold climate of Hokkaidō to hotter Okinawa. After this successful feasibility study, Denso obtained a patent to compress CO2 refrigerant for use in a heat pump from SINTEF in September 2000.[7]

    "The first commercial domestic EcoCute was marketed in Japan by Corona Corporation in May 2001, and several manufacturers sold 1.5 million units there by October, 2008.[4][8][9]"

    "By January 2005, 26 Japanese companies were producing more than 450 models of EcoCute machines, and sales of domestic units increased 130-150% each year between 2001 and 2005.[7]"

    etc

    Unless you have a reference that does contradict wikipedia?
  3.  
    Posted By: djhEcocute is just the brand name for all R744 (i.e. CO2) heat pumps


    Posted By: WillInAberdeenhttps://www.denso-am.eu/products/life-energy/co2-heat-pump/
    describes a R744 heat pump that is not branded 'ecocute'.

    http://library.mitsubishielectric.co.uk/pdf/book/Ecodan_QAHV_PISheet#page-1 describes another.

    Am not very interested whether Wikipedia is correct about this, and neither is the OP I suspect, because
    Posted By: WillInAberdeenCO2 heatpumps are a particularly good fit for heating DHW, which is not what Tom's client is looking for.
    •  
      CommentAuthordjh
    • CommentTimeMay 20th 2021
     
    You are the one who first mentioned CO2, R744, Ecocute so please don't criticise me for attempting to correct you if you think you have introduced a strawman. It's easy to find examples of R744 heat pumps that are not branded as Ecocute, because that's not what the brand represents. It must include a hot water storage unit as the wikipedia article states. As I said, we were both wrong.

    DHW is a design problem for hard-to-heat houses just as much as it is for easy-to-heat houses.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 21st 2021
     
    Am really grateful for the level of info and insight and willingness - nowhere but GBF!
  4.  
    Posted By: WillInAberdeen
    Posted by FT on the previous pageWill, it's time I looked at these 'heat pumps with newer refrigerants' which I meant above by sceptical 'suggestions otherwise for particular models' - I'd be grateful if you cd point me at relevant make/model(s).

    Sceptical, yes, as AFAIK maintaining CoP of 3 right thro winter is non-negotiable, both to make elect significantly cheaper than fossil thus justifying the cost, and
    to enable the renewable and CCS/H2 electricity supply to grow faster than demand does
    Several other GBF folks have mentioned the Vailant arotherm plus, SCOP of 3.9 when operating with a flow temperature of 50degC. Is using R290 refrigerant which also has a significantly lower GWP than R410 or R32.

    I am interested but have no direct experience yet.

    posted by Topher on another threadDaikin 3 H HT


    Tom, this Daikin 3 H HT, or the Vailant Arotherm Plus, both look like what you are after. Very high efficiency and capacity at >50degC flow temperatures to run radiators and DHW cylinders, SCOP >3.5 at radiator temperatures.

    They could almost have been designed for applications like yours...! :wink:
    •  
      CommentAuthorfostertom
    • CommentTimeMay 26th 2021
     
    So, this slow burning topic produces results - A2W as above and A2A. Three projects now where this will be valuable - thanks.
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