solar manifolds

Kevin_in_Denver_2

In some solar collector loop designs, the temperatures can exceed the temperature ratings of PEX.

Water itself can always store at least twice as much heat per unit volume as gravel. Water is also much easier to get out of a tank that has started leaking after, say, 20 years.

Ericjeeper

solar manifolds

Ok I got a deal on Ebay bought ten pex manifolds.. six are 1inch to six half inch ports.. and four others are 3/4 in and 4 ports half out..
Ok my plan is to hook the solar panels to the six banger. and place the manifold in the storage tank.To be used as a heat exchanger.. I need to maintain a flow of 12 gpm to meet manufacturers panels specs.
How many feet of loop can I get away with. I have a couple of already on the shelf pump options. and the largest is a Bronze 010.Taco. and I have a few red ones not sure of their number at this time..I was thinking Of going with 6 loops of 100 feet per.I would appreciate any help with this.I will use the same amount of tubing on another set of manifolds to feed the system from the tank., The water in the tank will just be my mass.. Once I get the system up and running and no leaks. I am planning on adding some clean creek gravel to the tank to act as storage mass..surrounding the tubing loops.
Ps The pex in the tank will be pex al pex unless someone can tell me why not to use it.Thanks, Eric Enk

Bob Gagnon plumbing and heating

copper heat exchanger

I would go with a copper heat exchanger mainly because it will transfer much more heat. You don't need anything slowing down your solar collectors. Hot Rod posted pictures of a solar collector that overheated and burst some pex piping. Kevin is right about the water. I too thought that gravel or sand would hold more BTU'S but have heard from multiple sources that water holds much more. How big is your tank and what kind of collectors do you have? Thanks for going solar, Bob Gagnon

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Ericjeeper

tank is 3 foot wide 7 feet long and 48 inches deep. will be made out of styrofoam six inch sidewalls earthen form.Basically buried with a concrete lid. as far as going with two huge loops of copper..I think That 1200 dollars is a bit hefty.. that would be two 100 foot loops one for supply and one for withdrawl to go to the house. I have six panels 3 feet wide 13 feet tall. Suncatcher I believe is the brand.. Used flatplate/.

hr

With pex submerged in water

I doubt that you would ever have a melt down. I agree copper would be a much, much better HX material. Probably 1 hundred foot loop of copper would get the job done.

Then again plastic tube is in most ground loop geo thermal.

I think your ideas of six loops would work well. pretty hard to put an exact number on the actual output of pex used like that. Flow rate, delta t, conductivity, etc would take some number crunching to pin down.

hot rod

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Kevin_in_Denver_2

collector loop stagnation

A drainback collector loop would eliminate those coiled exchangers altogether, and also ensure that the pex wouldn't see high pressures. Dry stagnation collector temps can be as high as 250 to 350 F. Don't forget that any collector loop design will probably see dry stagnation conditions at some point.

Ericjeeper

Yes but I want to use glycol in the panels and water in the tank. So How would I go about the drainback.. Use an open system? and hope that somehow the water will drain out of the top of these panels? The fittings are on the same end of the panel.I am planning on placing a t&p valve high on the panels and attaching a tube to a catch barrelback in the pumphouse.
I realize that copper would work better. But I ain't coming off of that kind of money..300 dollars I can get 600-1000 feet of half inch pexalpex.
I will be using type L copper from the panels down to the tank, and throughout the pumphouse

Bob Gagnon plumbing and heating

heat exchanger

I heard they now have submersible heat exchangers, constructed like a tankless coil from a boiler, I haven't found one yet, but I plan to use one on my next project. They are much smaller, and use much less copper and I assume they will be much cheaper. I used 5 lengths 1/2"x60' coil copper in my solar tank, and the heat transfer was less than I hoped, that is why I feel the pex won't work that well. Remember when the sun is shining you have to grab all the BTU'S you can get. Let us know how it works out. Bob Gagnon

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LarryC

What about reusing finned baseboard?

What about reusing finned baseboard? Providing the storage water doesn't chemically attack the fins or piping, wouldn't they provide a decent heat exchange? How about a decent sized plate heat exchanger external to the storage tank? It would mean a 3 loop system.

House load <= Storage tank <= Solar Collectors

LarryC

Ericjeeper

3 loops . Then I would have water out of the tank and in freeze danger. Otherwise not a bad plan. Thanks

LarryC

Big picture.

Eric, do I understand your system correctly? You have 6 external solar collectors feeding a buried insulated storage tank and then you are running water lines back to your house.

Where are the controls, pump, and expansion tank for your collector loop? Is the storage tank vented to atmosphere?

LarryC

Ericjeeper

I have an outhouse.

I built an imitation outhouse. that will sit on top of the concrete lid for the tank. The lid will be five inches of concrete ontop of six inches of polystyrene foam(pink board. R30, There will be a pump the controls and expansion tanks. I am not sure if one will be enough? I will make provisions for two in case one does not provide enough room. The lid will have a 2x2 hole in it.. I will cut foam plug and use a rock to hold it in place. Taper cut so it can not fall through/.So yeah it is vented as I am sure the plug will not be totally airtight
I went to Menards and bought all my copper ten sticks of 1 inch , buckets of tees and 90s.male adapters, female adapters, bushings. temp and pressure guage. Air vent.. T&P valve. totaled almost 650.No to buy the pex for the loop to the house..1 inch 300 feet. and probably will end up putting 1,000 feet for the HX in the tank. 12 loops of 83 feet should do it.. Lets hope