Hi,
(Admin: couldn't decide if this should be heat or controls, please move as needed.)
As I will be a man of leisure from the end of next week, my solar thermal (DHW) plans will probably be postponed until ~Feb of next year.
This gives me time to think harder about integrating the solar element with my existing mains natural gas tankless 'combi' heater, which although only ~80% efficient and unable to accept solar-preheated water, I'm not really willing to replace for a number of reasons. Mainly I want to reduce gas use altogether and not just put in newer ways of doing it (for example, we added 20cm of loft insulation yesterday ready for winter).
In the summer I intend to let the tank get hot (~90C) and so will have a TMV regulator to avoid water over 55C getting to the taps.
But what I think I need to integrate this with my gas combi without using the combi to heat the tank contents (ie I want to stay tankless when using gas at all as I think that that remains the most efficient and usable route) is another sort of thermostatic valve, but I don't know what it would be called or if it even exists for normal domestic plumbing... One of you here will be able to steer me I'm sure!
Basically I'd like something that clamps to the top of the tank, and if the tank is cold (eg <50C) diverts water to come from the gas combi rather than the tank. It should do this entirely mechanically with no electricity required if possible.
So, does this exist? What is it called if so?
Rgds
Damon