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Replace DCV with DHW Heat Pump

  • 22-05-2019 11:25am
    Registered Users Posts: 3,612 ✭✭✭ Dardania

    Am planning a renovation to my well insulated house, which has DCV fitted.
    I want to take the opportunity to address the space heating & domestic hot water while doing invasive works. And maybe clean up my environmental impact henceforth.

    Currently the space heating is gas from a system boiler, which is about 12 years old. Works fine (recently serviced) albeit old and I use a Nest for the single space heating zone, with TRVs on all of the rads.
    DHW is via local electric heaters like heated taps and an electrically heated shower. I got rid of the DHW cylinder a few years ago as we needed the storage space, and we didn't really need the body of water heated due to long dead leg to the kitchen, and electric shower fitted.

    The renovation will see a second shower room being added, so obviously it's not feasible to have 2 electric showers (forgetting about priority switches). Not to mention, the flow rate is abysmal - insulating your house well results in the attic cold water tank getting nice and "crisp" in winter. So a better solution for hot water is needed. Not to mention I have a, as far as is financially reasonable, to go for less carbon intensive lifestyle (so a switch to electrically powered everything + an airtricity account is the way to go).

    So I am considering integrating one of the heat pump DHW cylinders, like the Dimplex Edel or the Wiseair Heat Pump Cylinder. One option is to put it in the main body of the house (say the room where we dry clothes) but it feels to me all it will do is take the heat from the house (and therefore from gas).
    Or another could be to put it in the attic, and replace my DCV fan with it.
    Which anyway uses the waste heat from the house. Has anyone ever done anything like this?
    It will no longer be Demand controlled (looking at the manual for Dimplex unit it seems to either run constantly, or when hot water is needed, or some sort of temperature input...) but is that such a problem to have a reasonably consistent air flow in the house? The DCV wall inlets will still open and close due to humidity.

    And then separately, when funds allow - the old gas system boiler dies, I could replace that with a heat pump intended for the lower temps they're more comfortable with...

    Does this make sense?


  • Registered Users Posts: 2,820 ✭✭✭ air

    A gas combi boiler or a separate DHW only gas water heater sounds like a more economical / sensible option to be honest.
    If the existing boiler is working well I'd go with a DHW gas powered water heater, they're cheap as chips and very effective.You could just plumb it to one shower if you wanted.

    For the remaining electric shower, it shouldn't be difficult to insulate your cold water tank well enough to maintain it at 10-15C during the winter which should improve your flow rate considerably.
    You could look at running the feed to it through a coil of copper in the heated area of the house to improve it's input temperature also. Or could you change it to a mains fed model perhaps?