Loop Isolation Diagram

[shaniac]

Greetings everyone, I plan to install a second, closed, solar hot water loop for my current system. The new loop will face a different direction from the current loop. (East / West) I plan to use the current tank with its built in heat exchanger for storage.

 I need to plumb the system so that when the one loop is running, it does not draw a significant amount of flow from the other shaded, cooler loop. I have enclosed a diagram of what I think will work but I would like your thoughts if this is correct or if I need any other components. Because each loop will work at different times of the day, I can't close off any one side. Both loops will have their own independent pump.
Thank you!

[JW]

That temp gradient that you have listed as a hi and low side ? probably doesnt work, if to have whatever side running at 191 degrees fairenhight the whole circuit will be around that temp.


JW

[JW]

Ok, so your using coils in a tank to transfer heat between the two circuits, you should call this "tank transfer heat exchngr"

Because each loop will work at different times of the day

For it to work right, both pumps need to run at the time of greatest potential difference.


JW

[shaniac]

Thanks, you can ignore the heat graphic, I was just grabbing images from the net.

My main concern is that if one pump is running, it will not be pulling fluid through the non active loop.
 Thank you.

[shaniac]

Thanks again, sorry, there is only one looped pipe inside the tank, not two. The two solar loops OUTSIDE the tank (facing east and west) both connect to the same loop going through the tank. They are connected by T fittings at the in and out points.

[JW]

It will work the same if one flow path is internal and one external, but wont have twice the surface area without two seperate coils, using an enhanced thermal conductor fluid would be a benift... I figure gold or diamond is a better heat conductor than water or mercury.

JW

[shaniac]

Thanks again, but I guess I am not making my question clear. There is not an internal and external flow path. There is only one loop, kind of like a boxy figure 8, where the center line of the 8 is the internal heat exchanger inside the tank.

I will post a new image and will try again. Thanks for your help and your patience.

[shaniac]

OK, so looking at the above diagram the entire single glycol loop looks like this "[|]" with the two brackets being the two solar thermal arrays (East and West facing) and the center bar is the heat exchanger inside my solar tank. In the image, the flow of array 2 is pink and array 1's is green.

If the pink array pump is running (left side), will the check valve in the green array (top right side), keep the fluid reasonably still in the green array? And visa verse when it is time for the green array to run?

Because my two arrays are on the east and west sides of the roof, I need to make sure that when one array is flowing, the other is static so I am not circulating unheated glycol.

Can these two check valves isolate the two arrays reasonably well or do I need a different plumbing arraignment to make this work? Thank you so much for your second set of eyes on this. Cheers!

[XeonPony]

if you use a spring loaded check it should be good enough, personally I'd just use a normally closed solenoid tied into each pump, so only the running pump will be able to move fluid in its circuit and 100% automatic!

[shaniac]

Thanks Xeon, no, they are not spring loaded, they are flappers on a level section of the run. I originally had a spring loaded check valve but it caused so many issues that I replaced it and never looked back. Why do you think the flappers will not work?

Great idea on the solenoid, I will have to look into that, where do you get yours?
Cheers.

[XeonPony]

found retarded deals on ebay, I scored some 120psi pottable water all brass valves 40 bucks, each valve goes for 400 local.

So look there first and usualy find what you need, failing that any good plumbing place should have some thing

[shaniac]

Thanks, will do. Why do you think the flappers will not work?

[XeonPony]

they will more or less but if enough of a convection current is created when the pump is stopped it can leak through the flappers, I've seen in many a time in the water systems I work on, if you want pretty guaranteed isolation, a solenoid valve will do it!