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Heat Pump & Stove with Back Boiler

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  • 03-11-2013 4:21pm
    #1
    BarneyMc
    Registered Users Posts: 1,504 ✭✭✭


    My build is moving on fast and I'm trying to settle on a heating solution.

    My preference is an air to water heat pump (HP) as primary heat source along with a wood burning stove with back boiler. I'll be installing MHRV.

    The house has a 250mm wide cavity and will be filled with beads. My provisional BER give me an A3 rating and a primary energy value of 55kWh/m2/yr (although this assumes window U values of 1.5 which I hope to improve on). I work from home so there'll be a high level of occupancy.

    Here's some questions I have knocking about my head:

    1. Is the efficiency of a ground source HP significantly better than an air to water and worth the return on investment?

    2. I'll be using UFH on the ground floor but am worried that it may be hard to control on the first floor - is this the experience for those with UFH on the first floor?

    3. Should the HP and back boiler (stove) feed into a buffer tank rather than a 'normal' tank?

    4. I hope to allow for future installation of solar panels/tubes so will have everything in place for this. Using borrowed money to invest in solar (for hot water) now is wasted money in my opinion. Any thoughts?

    All thoughts welcome, thanks. :)
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    #2
    fclauson
    Registered Users Posts: 1,691 ✭✭✭fclauson


    BarneyMc wrote: »
    My build is moving on fast and I'm trying to settle on a heating solution.

    My preference is an air to water heat pump (HP) as primary heat source along with a wood burning stove with back boiler. I'll be installing MHRV.

    The house has a 250mm wide cavity and will be filled with beads. My provisional BER give me an A3 rating and a primary energy value of 55kWh/m2/yr (although this assumes window U values of 1.5 which I hope to improve on). I work from home so there'll be a high level of occupancy.

    Here's some questions I have knocking about my head:

    1. Is the efficiency of a ground source HP significantly better than an air to water and worth the return on investment?
    depends if you are buying or selling - I did not go GSHP but over 15 years it might have been cheaper

    2. I'll be using UFH on the ground floor but am worried that it may be hard to control on the first floor - is this the experience for those with UFH on the first floor?
    its the ground floor which is tricky !! - last year I used 150% of my PHPP number for heating - the HP cut in when not needed as it works on an external temp sensor - cold weather=higher supply temp BUT in a Passive house this is just not the case - this year I am awaiting the wrath of the women in the house as I turned OFF the heating- the floor temp has not dropped below 20.5 and rises during these warm days by about .25 deg

    So here we are in early Nov and no heating used as yet

    3. Should the HP and back boiler (stove) feed into a buffer tank rather than a 'normal' tank?
    you might never light the back boiler - we light the stove for effect but the room gets very warm - although it very atmospheric - but from the work I did I would suggest heat a normal tank - look at you plumbing costs and the return-on-investment
    4. I hope to allow for future installation of solar panels/tubes so will have everything in place for this. Using borrowed money to invest in solar (for hot water) now is wasted money in my opinion. Any thoughts?
    you know my view - do waste your money - go PV not solar thermal - my heating /h/w will run for FREE for the whole year - solar thermal cannot do this - use the grid as an inter-seasonal store

    All thoughts welcome, thanks. :)[/QUOTE]


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    #3
    BarneyMc
    Registered Users Posts: 1,504 ✭✭✭BarneyMc


    fclauson wrote: »
    depends if you are buying or selling - I did not go GSHP but over 15 years it might have been cheaper

    Family ground so won't be selling. I'll see how the prices figure for ground source but I'll most likely go with air to water.
    fclauson wrote: »
    its the ground floor which is tricky !! - last year I used 150% of my PHPP number for heating - the HP cut in when not needed as it works on an external temp sensor - cold weather=higher supply temp BUT in a Passive house this is just not the case

    I would have thought the thermostats in the house would override the external temp sensors?
    fclauson wrote: »
    you might never light the back boiler - we light the stove for effect but the room gets very warm - although it very atmospheric - but from the work I did I would suggest heat a normal tank - look at you plumbing costs and the return-on-investment

    The stove turned down very low (when let) would mean very little activity for the HP if all setup correctly. I'll see what can be done with this system.
    fclauson wrote: »
    you know my view - do waste your money - go PV not solar thermal - my heating /h/w will run for FREE for the whole year - solar thermal cannot do this - use the grid as an inter-seasonal store

    I'm not sure my budget can stretch for this just now but an advantage with the HPs is that PV is always an option in the future (I assume).


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