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What kw size air to water system do i need

  • 25-01-2021 11:09pm
    #1
    Registered Users Posts: 1,024 ✭✭✭ newhouse87


    Going with daikin system for 2600sq ft house, been quoted for 11kw by 1 plumber, just wondering what size would some with experience recommend, for all i know 11kw is perfect for my house size.


Comments

  • Registered Users Posts: 1,140 ✭✭✭ holdfast


    Depends on the insulations and rate of air changes. So more information need and even that it will be spitballing a figure out.


  • Registered Users Posts: 1,024 ✭✭✭ newhouse87


    holdfast wrote: »
    Depends on the insulations and rate of air changes. So more information need and even that it will be spitballing a figure out.

    going to be a newbuild so will be very well insulated to meet ber regs, as regard air changes i know nothing about that.


  • Registered Users Posts: 252 ✭✭ Biker1


    newhouse87 wrote: »
    going to be a newbuild so will be very well insulated to meet ber regs, as regard air changes i know nothing about that.

    The only way to be sure is to get a room by room heat loss calculation done based on the actual u-values and expected air change rate. Or you could just throw a figure of x w/m2 at it as many suppliers seem to do!!!


  • Registered Users Posts: 188 ✭✭ Latro


    newhouse87 wrote: »
    going to be a newbuild so will be very well insulated to meet ber regs, as regard air changes i know nothing about that.
    For new, very well insulated and airtight house 11kW would be too big.
    I'm confident that 99.9% of time 9kW heat pump will be big enough and most likely 99% of the time 7kW will suffice too.
    You should not "arm" yourself for the last 0.1% in this case. Just get cheap 50 euro, 1-1.5kW electric heater for that odd day every few years as an emergency supplement,
    but you are unlikely to ever take it out of the cardboard.

    You got old school advise from your plumber - oversize. This is common practice in Ireland. The level of expertise among installers here is very low.
    Do not oversize the heat pump.
    It makes more sense to slightly undersize it rather than other way around.

    Heat pumps are very efficient but not when used like oil/gas heaters.
    Rather than short bursts of heat, they should constantly (24/7) compensate your house with the same amount of heat energy that is lost at the time.
    It will assure very low flow temperatures, minimum on/off cycling and maximum comfort. This is where the heat pumps thrive.

    I do not recommend night rate tariffs unless you are happy to live in that regime. I wouldn't be.
    Also savings would be far smaller if any as the temperature drop substantially in the night. Ireland has very poor night tariff system.

    11kW x 24h = 264 kWh per day. This is A LOT, and it is unlikely that the heat loss will be even at 50% of that figure. Even on the coldest days of "the beast from the east".

    11kW heat pump is also likely to be 3 phase unit. That is substantial jump in costs. Make sure it is single phase unit in 7-9 kW range.


  • Registered Users Posts: 2,724 ✭✭✭ graememk


    Are heat pumps measured in heat output or electricity input?


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  • Registered Users Posts: 188 ✭✭ Latro


    graememk wrote: »
    Are heat pumps measured in heat output or electricity input?


    Output, at certain ambient temperature and water flow.


  • Registered Users Posts: 2,724 ✭✭✭ graememk


    Latro wrote: »
    Output, at certain ambient temperature and water flow.

    Thought so, so a 11kw would use 3-4 kw of electricity, which would still be single phase (or maybe single phase but inverter driven)


  • Registered Users Posts: 11,209 ✭✭✭✭ KCross


    graememk wrote: »
    Are heat pumps measured in heat output or electricity input?

    :)

    It is a very common mistake that someone gets a quote for a 12kW heat pump and things that the HP is pulling 12kW from their ESB supply!

    The rating is output.

    What you need to see is the COP which then gives you an indication of what it is actually pulling from your supply.... usually as you say, about 2-4kW depending on HP.... which is what HP's are good at.... feed it 3kW and it gives you 12kW.... 400% efficient!


  • Registered Users Posts: 3,292 ✭✭✭ 0lddog


    What's the score with warranty accountability when a plumber supplies a unit from the likes of Daiken ?


  • Registered Users Posts: 188 ✭✭ Latro


    0lddog wrote: »
    What's the score with warranty accountability when a plumber supplies a unit from the likes of Daiken ?


    Zero if he is not manufacturer certified.
    You would need to find someone to inspect and sign it off for a fee.


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  • Registered Users Posts: 10,926 ✭✭✭✭ Calahonda52


    Latro wrote: »
    I do not recommend night rate tariffs unless you are happy to live in that regime. I wouldn't be.
    Also savings would be far smaller if any as the temperature drop substantially in the night. Ireland has very poor night tariff system.

    11kW x 24h = 264 kWh per day. This is A LOT, and it is unlikely that the heat loss will be even at 50% of that figure. Even on the coldest days of "the beast from the east".

    11kW heat pump is also likely to be 3 phase unit. That is substantial jump in costs. Make sure it is single phase unit in 7-9 kW range.

    Clearly you have no idea how a heat pump works.
    This post must be a contender for the worst post in 2021 and we are still in January
    11kW at your math is 10,000 per annum.


  • Registered Users Posts: 404 ✭✭ ec_pc


    Our house is approx 2750 Sq feet, air tight, triple glazing etc etc, combination of UFH downstairs and rads upstairs.

    Our heat pump is 11.8 KW and current COP is 4.9. I engaged an energy consultant prior to the design of the house and he wrote a spec which was then put into the tender docs.

    Heat pump proposal was reviewed and approved by him prior to installation. Consultant was well worth the money in my opinion as you only get 1 shot at this really.


  • Registered Users Posts: 2,868 ✭✭✭ Borzoi


    newhouse87 wrote: »
    Going with daikin system for 2600sq ft house, been quoted for 11kw by 1 plumber, just wondering what size would some with experience recommend, for all i know 11kw is perfect for my house size.

    Daikin have selection software for calculating heating loads, ask for a copy. ðŸ˜


  • Registered Users Posts: 188 ✭✭ Latro


    Clearly you have no idea how a heat pump works.
    This post must be a contender for the worst post in 2021 and we are still in January
    11kW at your math is 10,000 per annum.


    11kW is 10,000 per annum? 10000 of what? Where did I calculate that?
    I have no idea what you mean by that.


  • Registered Users Posts: 1,024 ✭✭✭ newhouse87


    my plumber sent the plans to to daikin and they recommended 11kw, seems to be a few thousand euro saving if i buy from the uk, im currently email a crowd there, doubt i will buy from the uk but seems mad to have such a price difference for the same unit.


  • Registered Users Posts: 3,292 ✭✭✭ 0lddog


    newhouse87 wrote: »
    my plumber sent the plans to to daikin and they recommended 11kw, seems to be a few thousand euro saving if i buy from the uk, im currently email a crowd there, doubt i will buy from the uk but seems mad to have such a price difference for the same unit.

    What ever you do, dont get caught out when you need service for it.

    Read this and shiver

    :eek:


  • Registered Users Posts: 1,024 ✭✭✭ newhouse87


    Does anybody know are thermia more expensive than daikin, just trying to compare plumbing quotes i got.


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