Could someone please advise me if it is possible to combine an immersion heater with a combi boiler? I have a 10KW PV solar system installed and produce plenty of excess electricity every day. It would be good to power an immersion heater with some of the spare electricity as I could then significantly reduce my gas usage.
Firstly I wouldnt do it myself. I have known people use a solar system to fuel an immersion heater but not with a combi. You could change your boiler to a condensing system boiler and make the necessary alterations from there.
However, I suppose if you set up a separate hot water system alongside the combi it would work. By that I mean a cold water tank in the loft feeding a hot water cylinder heated only by the immersion feeding a separate hot water outlet.
You couldnt mix up the hot water pipes from this system and the combi of course as they would operate at different pressures.
Whether or not you could link the coil of the hot water cylinder to the central heating side of the combi or not - in effect treating it as a radiator to heat the hot water on this system when the sun isnt shining - is an interesting thought. It would need a thermostatic control to stop the hot water in the cylinder overheating and still be cotrolled by the room thermostat. Maybe some types of combi system could treat the cylinder as a separate zone. In any case I'm getting out of my depth now. I doubt if anyone has ever tried it and I dont advise you to be the first.
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