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13kw Danfoss DHP-AQ Running costs

  • 13-02-2023 1:25pm
    #1
    Registered Users Posts: 1,013 ✭✭✭


    Running a 13kw Danfoss DHP-AQ Air/water system on a 3000sq ft house. New build 2015, A2 rating, airtight build, I wondered how my annual usage compares to others.





Comments

  • Registered Users Posts: 12,091 ✭✭✭✭Calahonda52


    You need to give us the data rather than expect us with hearing aids to interpret the graphs.😎

    “I can’t pay my staff or mortgage with instagram likes”.



  • Registered Users Posts: 1,341 ✭✭✭Nelbert


    There's more than your BER and energy usage in play too. Particularly during the cold snap if you had a higher set temp your HP would have been working harder than someone in an identical house with a lower set temp.

    Insulation, air tightness and the householders desired temp all in play.



  • Registered Users Posts: 1,013 ✭✭✭Curious Geroge


    Thanks @Nelbert @Calahonda52

    180mm full fill bead cavity, full airtightness (no report available), A2 rated, MHRV, temp set at 21 all year round.



  • Registered Users Posts: 805 ✭✭✭keno-daytrader


    2300 sqft detached house, MVHR, Heatpump A2W 8 kw, temp set at 21.5c.

    We used 238kWh for heat and 89kWw for hot water in Dec, it was the most we've used in a month because it was so bitterly cold.

    Jan was 169kWh heat and 72kWh hot water.

    Perhaps worth it to get an airtightness test, I did our airtightness when building and was so worth the time as I dont think contractors or engineers give a hoot what it is, but will save so much money in the future of the house, if its done right.


    How is the attic insulated?

    ☀️ 6.72kWp ⚡2.52kWp south, ⚡4.20kWp west



  • Registered Users Posts: 1,013 ✭✭✭Curious Geroge


    @keno-daytrader , much better that what I'm seeing tbh. I wouldn't expect a 13kw to be doubling the kwh usage. Airtightness done on the build, wrapped hollowcore on all floors, 220 metac + airtight + 40mm insulated boards in the attic.



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  • Registered Users Posts: 805 ✭✭✭keno-daytrader


    Whats your flow temp in your underfloor heating?

    Ours was eating electricity when left on auto, I think that installers leave it on "auto dummy mode" so they dont get call backs.

    Now I dont let the flow temp go over 30c on even the coldest of days/nights and this has saved us so much money and the COP improved dramatically. Usually mine is between 26-28c.

    Obviously you cant run rads that low, but we have underfloor thru out the house.

    ☀️ 6.72kWp ⚡2.52kWp south, ⚡4.20kWp west



  • Registered Users Posts: 1,375 ✭✭✭DC999



    Dumb Q and don't have a heatpump. But will at some point so learning. Could you not run rads at a very low temp but leave them on much longer? 30C on a 5 foot rad has to be putting out a low, slow heat if on most of the day? I've an small oil filled electric rad (700w) and it runs all day and heats the 5x5m sitting room / kitchen space perfectly. Ok, it gets to 60-70C but it's a much smaller surface area than a wall mounted rad. It can't rapidly warm a room - far from it, but we don't need that.

    What's lowest rad temps that works in the real world for on a HP? I'm curious to see what size of HP would work for us (using a low and slow temp). Our gas boiler can do something like 15kW - we only ever need that sort of capacity if heating isn't on all day and gets turned on before you get home. But we don't heat our house that way anymore. We keep the downstairs at a nice temp constantly during the day and heat rises upstairs. Don't need to heat upstairs a lot then.



  • Moderators, Home & Garden Moderators Posts: 5,519 Mod ✭✭✭✭graememk


    The hotter a radiator gets, the more heat it outputs. But very roughly (at a quick glance at a joule spec sheet) If the flow temperature was halved, the power of the radiator could be a third or a quarter of the output. thats the big gotcha with radiators. Its balancing the flow temperature with the actual radiator area. (to make up for the heat loss of the room)

    thats where underfloor heating works so well at low flow temperatures, its area that it can emit heat is the size of the room!

    Its all a balance of radiator size and flow temperature, lower the flow the more radiators (or insulation) you need to maintain the room temperature.


    A heat pump can heat anything even a drafty barn at a low flow temperature, aslong as there is enough radiators and still maintain a reasonable COP.



  • Registered Users Posts: 1,013 ✭✭✭Curious Geroge


    I'm not sure, do you know how to check this on a danfoss unit ?



  • Registered Users Posts: 805 ✭✭✭keno-daytrader


    Sorry I have a Mitsubishi, it should all be in your manual.

    ☀️ 6.72kWp ⚡2.52kWp south, ⚡4.20kWp west



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