Solar panel installation question

[cleancloths]

I recently bought some Sungrabber panels on e-bay. They are 2' wide by 20' long. They claim that they should be installed in what I consider a very strange manner. At one end the right side of the header says inlet and the left side says outlet. While at the far end there are caps on both ends of the header. It says something about an integral disc being in the feed header such that water comes in from the right and flows down half the tubes and then returns up the other half the tubes. You then connect the outlet on the left of the top header to the inlet of the next pannel and the oulet goes to the pool. I did that and with about 6gpm of flow was getting a 4 degree temperature rise. But what I noticed was that standing at the header where water was going in and out the panel on the right (nearest feed) was very hot and the one on th left was cold. This seemed wrong.

So, I repiped it so water flows in the top of one panel and then out the other end. That end is then connected in series with the second pannel. Without adjusting valves my flow dropped to 4 gpm, but my temperature rise went from 4 up to 9 degrees. Thus, instead of getting 12,000 BTU/Hr I am now getting 18,000 BTU/Hr.

Does anyone know anything about these supposed integral discs? I assume I am better with this second setup, but let me know if you think otherwise.

[Poconos]

A few basic rules for solar panels. You always want least flow resistance for maximum flow. Next, always input water at the bottom, take out the top. This is so air can be purged from the tubes. The 'disc' you mention is probably a valve. I can only speak for my 4x20', forget the name, but that valve when closed lets the in and out be on the same end. With that valve open, water can flow in one header, down the tubes to the header at the other end and out the top of that header. Lowest flow resistance configuration. I would run this way and parallel both panels. Maximum flow means a lower TEMPERATURE rise and the panels should be cool, but it also means maximum heat transfer to the water which is the important parameter.
Al

[tphaggerty]

Bought one of those Sungrabbers for my brother in law. It does have the disc. Basically, it turns the 2 x 20 into a 1 X 40, the water goes in the input, goes up HALF the tubing to the other pipe, comes back down the other HALF and exits at the output. If you want to put more than one, it makes sense to bring and input to EACH panel (otherwise, if you go input->output->input->output, you are just creating a HUGE series panel and that is going to restrict your flow and make the panel less effiecient).

[cleancloths]

What does the disc look like? I could not see anything. If I hold the header up to the light it looks like a straight through tube. Perhaps they sent me the wrong item? In any case the way I have it now I am flowing water down the length of one panel into the far end of the other and back up to the top where I take it off to the pool. IF there is a disc it is not doing anything as the panels are realatively cool the entire length. When I did it as they suggest the first panel stayed hot and the second was cool - so I know that was not good.

[NWMNMom]

heads up, one of our panels had been prepped backwards at the factory (the wrong ends had lables for inlet, outlet - so it was basically upside down) We turned it around and it worked fine.

[mneal]

I bought a couple of those sungrabbers but have not installed them yet. I have a IGP with spill over spa and was not 100% sure how I wanted to plumb it. How did you guys plumb yours?