Question about combi boilers and hot water cylinders

[graduate_owner]

Here's a question for any plumbers out there.

A friend of mine has a mobile catering business and is in the process of converting an outhouse into a dedicated food prep area. He has an oil fired combi which will run in the usual way. He also has solar panels and wants to make use of surplus energy using a so!ar switch to heat water in a hot watet cylinder, but that is what is normally done with a conventional system.

So, would it be possible to connect an indirect hot water cylinder plus solar panel fed immersion heater ( with cold water cistern feed) into the heating side of the combi, and have the hot water from this feed a separate tap over the sink?
This would allow him to have free hot water when the sun shines, but to be able to top it up using oil rather than expensive electricity when necessary ( eg weekly to prevent legionnaires' disease.) during summer. He would also have the instant heat water from the combi during winter when the surplus solar energy would be minimal, from the normal dhw tap.

This sounds feasible to me, but am I missing something? Regarding installation costs, he will do the work himself and has most of the materials needed, else I think the extra costs would make it uneconomic.

Any comments?


K

 

[Terry - Somerset]

I'm no expert but combi boilers normally work on 1 - 2 bar water pressure - but an indirect system fed from a cold water cistern and hot water tank are likely to be 0.5 bar or less depending on the height of the cistern above the combi boiler or tap.

Unless I've misunderstood the question, trying to mix different water pressures seems a recipe for disaster!!

Terry

 

[graduate_owner]

Interesting point Terry. Basically I was considering the cylinder coil as another radiator.

K

 

[Wuffles]

This sounds like a fairly standard "system boiler" setup to me? Hot water held in pressurised tank, topped up by either oil boiler or immersion element?

I've just re-read you said combi, but I've written this already, perhaps worth some sort of consideration anyway.

 

[nev]

Dunsley neutraliser.

http://solidfuel.co.uk/pdfs/central-heating-link-up.pdf