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Discuss Woodburner/heat pump/solar heater combination in the Renewable Energy area at

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  1. jbolland

    jbolland Guest

    I'd like advice on best way to incorporate these 3 heating options. I've ruled out a 3-coil cylinder on cost grounds. I'm also aware of the regulations on woodburners and unvented cylinders.
    I'm looking at 2 options, each with 2 cylinders.
    In option 1, the twin coil (DHW)cylinder accepts heat from the woodburner and the ASHP, and the single coil cylinder accepts heat from the solar heater.
    In summer with no woodburner, the solar heat is transferred to the DHW. I can see there will be an efficiency loss, but the cylinders will be adjacent so maybe not too bad. When the ASHP is on, residual heat after the underfloor heating will pass to the solar cylinder and act as a heat store. I'll set the solar cylinder thermostat at 50C so that up to 50C, the heat pump circuit pumps, and over 50C the heat store circuit pumps.
    In option 2, the woodburner feeds the single coil cylinder (as well as the radiators). Heat for DHW is pumped across. Again there will be an efficiency loss.
    I'd like opinions on what would be the better option, and also if there are any other methods. My 2 pdf files are 13kb each, so I'll post the second one separately - I hope this is OK:confused:

    Attached Files:

  2. oldplumber

    oldplumber Guest

    :eek::eek:Nice pics you are aware that you are putting in at least 2 potential bombs into your home, and i presume you are intending to do it diy. That in mind i wont be offering advice, apart from, call in a qualified engineer who specialises in solar and woodburners, both of which can cause specific issues.

    Has your home been surveyed to see if it is suitable for an ashp, ive seen people paying more in electricity to provide a poor heat output than could have been achieved using gas and a properly modulated boiler, which over a 10 year period would cost less than your plans and be more efficient on co2 output.

    I dont think this forum is the place to be asking advice on systems that could easily cost £20k plus to install and ensure they work properly.:rolleyes:
  3. gakmonkey

    gakmonkey Guest

    Have you considered a thermal store instead of unvented?
  4. Renewable M

    Renewable M Guest

    hi, we've done loads of these systems. if you want to get in touch, advice costs nothing.

    you are missing a few points in your rudimentary description, to be sure.

    out of curiosity, who is actually doing the work?

    feel free to bend my ear in office hours on 07861 730 648 (matt)

    Combining heat sources is very popular these days. If you get this right it will be spectacular, if you get it wrong, as the previous poster suggested, it will be a liability. getting it right is not too much of a minefield.


    p.s. this is the place to get advice...
    Last edited by a moderator: Feb 25, 2010
  5. jbolland

    jbolland Guest

    Hi matt, thanks for the positive response. i'm out of the country at the moment but will contact you when I get back next week. I've had a small redesign and will discuss with you - basically reverting to one twin coil solar cylinder for the 3 inputs.
  6. quality

    quality Plumber GSR

    Large buffer tank is the way to go
  7. unguided1

    unguided1 Plumber GSR

  8. Wet Bandit

    Wet Bandit Guest

    Heatwebs right. I work as a solar installer and have fitted several DPS thermal stores to great success. They're the best solution for incorporating several heat sources. I'd steer well clear of ASHP's though - can be thirsty on the lecky.
  9. unguided1

    unguided1 Plumber GSR

    ASHPs only tend to be thirsty on electric when they are asked to work in parameters they were never designed to work in, therefore it is important that should anyone decide to go down the route of buying one they should use an MCS accredited enginer to correctly advise them and also gain them the grants

    Here is a list of MCS accredited engineers [DLMURL=""]The Microgeneration Certification Scheme MCS[/DLMURL]
    Last edited by a moderator: Mar 31, 2017
  10. heinz57

    heinz57 Guest

    I can see the solar problem, the wood burner im not so sure i can fully understand it. He has open vent expansion and 1 heat sink rad, probably needs more than that - 3 to 4 maybe? would a bypass valve be the answer as well on the burner?
  11. oldplumber

    oldplumber Guest

    sorry about the caps hit the wrong button:)
  12. jbolland

    jbolland Guest

    Many thanks to everyone for the advice, it has been very helpful and useful and has given me a lot to think about. I've taken on board the need for a separate hot water storage cylinder, and simplified the original plan. The storage cylinder (open vented) will now receive from the woodburner via 28mm pipe (convection flow). Another simplification I've made is to pump the hot water from the storage cylinder via the underfloor heating after it has passed through the rads. The heat pump will be installed between the rads and the ufch so that the heat pump will heat up the ufch bit, and pass the residual hot water back to the cylinder. The rads will only be lukewarm until the wife gets up and lights the fire. The heat pump should then cycle off when the temperature picks up. The solar heater will help during the day and I'll also use it for the domestic hot water. I hope this makes sense, still got around a year before I start to install things. plumbing rev 6 model-001.jpg Sorry i seem to have lost the ability to post pdf file, this is a jpeg.
  13. ecowarm

    ecowarm Guest

    You're still showing a boiler heating an unvented cylinder and if the boiler is solid fuel, this is dangerous and not allowed.

  14. jbolland

    jbolland Guest

    [Ecowarm wrote: You're still showing a boiler heating an unvented cylinder and if the boiler is solid fuel, this is dangerous and not allowed.]

    I can understand and agree that if the woodburner is gravity feeding into an unvented cylinder then there is a major risk, which would be made worse if the feed was direct.
    But I'm failing to see the risk if:
    1. The indirect unvented cylinder is heated by a pumped system from the WBS and incorporates the supplied spring to close control valve on the heat inlet. Surely this will prevent any cylinder overheating? Power failure will also close this valve.
    2. The WBS has a gravity means to dissipate heat when the pumped system stops. (I've got the 213L vented heat store).

    I envisage a "worst case scenario" to be a fully loaded WBS, a heat store full of hot water, and a power cut. under these conditions the unvented cylinder would be isolated from the heat supply and the water in the heat store would possibly be raised to boiling point and vent off. I don't see an "unsafe" condition.

    Separate from this argument is the fact that my unvented cylinder will be in the garage, below the level of the WBS which is on the 1st floor.
  15. ecowarm

    ecowarm Guest

    I think the only way you can do it is if the unvented cylinder is heated from the thermal store and not from the wood burning stove

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