Electric/solar water heating

[Timgo]

Eh up pipe smiths,

I’d welcome some advice or comments please from the Navitronicenti. I’ve been reading the forum with interest, particularly the discussion on xs heat dumping as I’m planning a solar water heating installation for my son in his Newcastle flat. There is an existing gas CH/HW boiler which is serviceable, but my inclination is to separate the CH from the HW functions completely.

The outline plan is for a thermal store (172l) with a solar circuit, mains pressure cold-in hot-out for HW for kitchen and (shower only) bathroom, and supplementary heating by emersion heater(s) only. The heat dump could be by a third coil to the bathroom radiator/towel rail. I would plan to use cheaper night electricity to boost the HW in winter  and hope this would be cheaper (and more ecological -less gas hydrocarbons used, green electricity specified) and just as easy to plumb in.

Has anybody out there conceived or installed such a system? Any pitfalls to avoid? Can I install two emersion heaters (would there be an advantage?) -one standard in the top of the tank, and one lower in the tank to ensure plenty of HW at cheap night rates when solar is low.

Plumb crazy and touched by the sun

Timgo   

[Ian]

As far as I can see, it all looks very workable.

Question (as I have not researched this myself) : Can you get Econony7 from the green energy providers ? I know you can from the conventional utilities but I cannot recall ever seeing anything about it from a green supplier.

You CAN provide 2 immersion heaters and assuming the water is very cold and the tank totally devoid of solar heat, you would need 2 x 3 kW immersion heaters in order to totally heat the store in a 7 hour period. I would suggest that you mount both immersion heaters as low in the tank as is reasonable in order to maximise the potential heat storage capacity.

It is easy to provide a system that works in normal circumstances; it is a little more difficult to plan for all eventualities. Think about the likelihood of abnormal behaviour and balance the risk of this happening v the downside and what you (your son) would be preparared to live with. My thought was in the middle of winter when the solar component would be low. What would happen if a few people were to stop over and want a shower in the morning ? Would there be enough hot water and what would you do about it if there were not ? Currently there is no capability to top up the thermal store in an emergency outside of Economy7 hours. Is that OK ? (This is very simple to rectify - even if it means paying full whack for the electricity - but is that OK ?)

I hope this helps.

regards,
Ian

[Timgo]

Eh up Ian

Thanks for the advice. I had envisaged that the bottom emersion heater would "trickle" top up the tank when needed, in winter using Economy 7, but that the top emersion would be on a separate circuit for "boost" HW at any time if HW demand exceeded supply. I guess the controller and circuitry would need to be carefully thought about.

Plumb crazy and touched by the sun

Timgo