Solar panel installation question

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.

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

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).

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.

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.

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?

We have a diverter system and plumbed all of ours so that it runs from diverter to a central pvc that Ys off to simultaneous INs and a simultaneous OUT that runs back to the diverter and return. We have ours mounted on a rack system that stands upright on the north side of our pool as we have no left over southern exposure between the pool and the woods.

take encaps off, look though each header, the one you can look through gets the caps (where the water makes a u turn), the one you can't look through gets the input/output connectors.

If you do connect more than 2 units, it is beneficial to remove the baffles (some units allow for that) in the input/output ends of all, install the input connector there and a cap, install the other cap at the far end, with the output connector, feed into the next etc.

I looked through both ends and can see clear daylight through both ends, so I can only conclude the panels don't have the discs they talked about. Anyway, I just came in from repiping the sytem. I have the two panels next to each other with a flexible connector tying them together at both ends. I am feeding water into one tied header and withdrawing from the tied heater at the other end. Seems to be working quite well this way.

CleanCloths has gotten to the nub of the matter: An increase from 12kBTU per hour to 18kBTU per hour. While it's true that more flow generally means more heat, I suspect you had blocked off half your panel and therefore were only getting half the heat. Replumbing doubled the length and with it the resistence and GPM, but increased the heat absorbed.

That's my guess. Normally that "disk" or valve forces the water coming in one port to go the length of the panel one half (1' width) then come down the other. Opening the valve allows the water to flow through the end tube without hitting the panels.

Bottom line: You BTU/Hour added to the pool jumped 50%. And BTUs are REALLY what heating is all about, not temperature.