The dhw tanks are seperate volumes so you heat them in order, sun gets first up to temp and then starts next one ,if its out long enough, and you use tanks in order too, basically english sun is unreliable so capture as much heat as you can whilst its out, and use when its not, it also means that if theres no sun you can just heat up 1000L with the gas or p.v.powered immersion not the whole 3000l, hence each tank is seperate and needs its own expansion. I must admit theres aspects of the system im still getting me head round, this being our second winter using it. The system was designed by a company called british eco, i think they did a good job, but thats all they did a good job in. They subbed installation to another company, they got it done inthe end, but start to finish was 10months. I dug the service trenches from the stables(new boiler room) to the house myself to save money, did it over a week, lots of trenches and the worst dig ive ever done for the amount ofservices and unknown water pits in the way. They were meant to come lay the pipe the following week. They didnt come for 2months. needless to say trenches werent trenches by then!
I see your point on inhibitor, maybe just covering all bases. Do you guys pump straight into your rads or do you heat exchange? U should now, the house it heats is massive 27occupants and one ancient c/h system all plumbed in steel with big old cast column rads, so we heat exchange coz theres no way we were power flushing.
Regards costings, 65k including solar thermal and connection to a secondary building which is used part time(we rent it to groups, run courses from there etc)This means loads of buried insulated pipes and they cost loads.
We were able to secure 35k funding but we had to jump through some massive hoops, the most interesting of which is allowing local schools to use as energy project. One ofthe techie guys i live with designed and built hardware and software connected to all our renewables(solar thermal,p.v,boiler) and internet, it gives instant readouts of energy produced, historical figures, and basic conversions to units of energy kids understand like miles driven in average car, light bulb hours, cups of tea u could make etc. This gets sent to 2 touch screen units in our house and to web address anybody(like theschool kids) can access. Its really neat(and way beyond me). School havent done a project yet but hoping they will this year. Its great to be able to see on a screen exactly how much energy you produce and direct difference between cloudy/sunny day,softwood/hardwood. Cant remember what web address is right now, but will post soyou can look if interested.
Posted some pics of our new shed here:http://arbtalk.co.uk/forum/firewood-forum/24086-show-me-your-firewood-storage-shed-rack-please-4.html
Anyway time for bed, enjoying this thread. Sorry if i waffled.