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Hi guys,

I’m designing a new kind of solar heating system. I’m just an amateur and don’t know enough about technical terms to run google searches for pieces of equipment to see if what I need exists, so I was wondering if you could help please?

What I’m designing is a solar water heating system that heats water in a closed loop.
What I need is to be able to introduce water into and draw it out of the loop whilst still maintaining the heating effect, which will require a pump or two to overcome the laws of thermodynamics.

At one end of the loop I need to be able to continually draw water in via circulation caused by thermodynamics. This end is also the cold water to system input end.
At the other I need to draw water according to thermodynamics and recycle it to the start of the system, and draw off hot water per demand.

I’ve worked out the thermodynamics and the closed loop, what I need help with is
A) a solution to being able to temporarily prevent hot water from recycling and re- entering the closed loop, whilst switching on cold water input into the closed loop when draw is placed on the hot out valve of the loop.
I was thinking a pump that has one out, two ins and a switching shut off valve of some kind connected to a negative pressure switch on the system draw... does such a pump exist? So a switching dual input pump with one output? If it does, how would I activate it? I Was thinking a pressure switch on the system out draw?
If it doesn’t, can anyone suggest a solution- I can’t get my head round it and I lack the plumbing technical know how.

B) Second I need to be able to draw water off the out end of the loop per demand, whilst actuating the cold input and . Was thinking a tee-junction with a pressure-set one way valve on one output, the other output of the tee recycling to the start of the closed loop. The pressure change when the pump for the heating system activates would draw hot water through the pressure valve, which would otherwise be shut thus forcing the water to circulate the loop according to the laws of thermodynamics. So I think I have that covered.
Except a name... does a valve exists that will not allow water through when high pressure is on one side, but will allow water through when pressure decreases on the other? Or some kind of pump?

I hope I explaining this right. It’s kinda complicated and I don’t have the know how to give proper terms. Please ask me if anything is unclear.
I’ve enclosed a rough diagram of what would be ideal, to give you a clearer picture.
if you can tell me how I can do it, and what the parts are called, that would be great.

Thanks in advance for any help you can offer guys, i really appreciate it.


king of pipes

Gas Engineer
Advent Win
I don't think so what you are proposing could be disasterous we are not here to design heating systems , plenty of renewable companies offer systems designed and thoroughly tested before going into production, you need the relevant qualification to design and install these type of systems. Kop

Thanks for your reply. I don’t see how it could be disasterous. It works under the principles of thermodynamics and convention to push water round the system rather than any form of pressure. I’m incorporating an expansion tank into the design in case anything should go wrong. And it’s powered by the sun and has no electrical, electronic, or gas driven parts.
I’m not looking to install it commercially. I have a small holding/eco home which is off grid. I intend to use the system to heat that.


Gas Engineer
All solar systems are closed loop. Similar, in principle to sealed heating systems.
These are kept closed, because you don’t want a content supply of fresh water. You ar adding oxygenated water constantly and this will cause no end of problems.
Solar is filled with a glycol mixture to prevent freezing. Yours will freeze in winter.

Keep it indirect
You really need to go back to some basics if you show anybody esp us on a public forum your design will never be 'prior art' and you cannot get it protected . I am an inventor/designer of heating components with a number of devices in use/sales etc you really need to follow the correct procedures - get advice and then design your system privately


Try the Centre for Alternative Technology website, and see their courses and bookshop and free information service. Go on one of their courses and you could learn to do a safe DIY job.

There are numerous hippy publications by Alternative Technology publishers on this sort of thing as it is perfectly possible to do a DIY job, but do yourself a favour and learn from other people'e experience. Buy some books on the subject. The L.I.L.I.'s book is probably very good: Also Brenda and Robert Vale's The Self-Sufficient House would be good reading for you. There is an excellent section on how to make a collector from an old radiator - something I keep meaning to try myself.

If you want DIY solar, best to do some reading up on it first: the sun is an uncontrolled heat source and so, in theory, you could be building a bomb.

This forum may not be the best place to discuss DIY solar. Modern commercial solar systems can be very efficient and so there is the risk of using high-output components that are designed to work under quite specific conditions, which coupled with a lack of knowledge and an experimental attitude, could prove fatal.
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