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.

Finally got the SunGrabber folks on the phone today. They told me I would know if the disc was there as it has a big red handle to control it and you cannot see through the header. They tell me I was shipped the inground units rather than the above ground units - which is fine by me since I have an inground pool, just did not want to pay more for what looked like the same panels.

I have the panels tied in parallel now and they are working great.

I would recommend a slight change in the setup of the panels,
on the supply end of the first, I would cap the end of the header that is currently tied to the second - this will force all water through panel 1 to the opposing end, where you should then push through the short pipe to panel 2 and cap that side of the input header, forcing all the water through the second panel then back to the pool.
it would eliminate tying the panels together at BOTH the INPUT AND OUTPUT headers, which can cause unforseen problems and or performance issues (not saying it will, but a chance exists.).

I had it the way you suggest at one point because I needed another flex connector to connect it in parallel. Why do you feel hooking them in series is better than hooking them in parallel? I understand that if you hook them in series you will generate hotter water, but by hooking them in parallel you extract more total BTU's which is the name of the game.

What "unforseen" problems do you think might happen?

The 2 Panels are designed to run in series (by manufacturer) utilizing a standard pool pump, there are many smaller variances such as pump size, GPH , but that is the basic starting point.
It has something to do with the cross sectional area of all the small channels in the panel adding up to the cross sectional area of your input/output pipes.
Running in parallel is like taking your 1.5" pipe, changing it part way through to a 2" pipe, then back to a 1.5" pipe - this can cause inefficiencies such as stagnant or "slow" areas on the panels where there is slightly more resisitance in some of the small channels due to production imperfections (water takes the path of least resistance).
If a portion of your panels malfunctions (plugs up) you will see that immediately on your pressure gauge if they're in series, however, the only way to tell when in parallel is to physically touch the panels and feel for hot channels since your 1.5" outlet is going to dictate your backpressure in that setup scenario.
BTU should be the samel whether you run in parallel or in series since your surface area exposed to the sun is the same thus collecting the identical amount of energy) and your pump is pushing identical GPH and heat transfer to water at any temperature (outside of steam) is constant.

I'm no expert, but have had numerous discussions on this topic with a friend of mine who is prior to both him and me installing these systems on our pools.

Bottom line is to do what the manufacturer recommends since they went through all the design work and testing prior to bringing the product to market.

Sorry Matt, but I don't buy it - In my previous life a was a chemical engineer working in plant operations. When you run in series you create higher pressure drop not lower. Further, the driving force for heat transfer is much lower at the end of the last exchanger when you run in series versus in parallel. Thus, a parallel operation will extract more heat, albiet with a lower temperature rise. Without changing any valving I could only obtain about 6gpm through the panels when in series but and running 12 gpm total when in parallel. As I mentioned in a previous post when in series (at the same point in the day - maybe 10 minutes apart) I was extracting heat at the rate of 12,000 BTU/Hr in series and 18,000 BTU/Hr when in parallel. That is a 50% increase in heat addition to the pool.

Check this link: http://www.sungrabber.net/Customer_S...20ING_2007.pdf

They suggest installing them in parallel - the way I currently have them.

I got most of my information from a friend who is an environmental engineer - he spends most of his life designing cleanup systems that require many miles of plumbing/extraction chambers etc and intricate measuring devices.
When we researched and purchased our systems he even went as far as calculating the cross sectional area of the tubes to see if they equal the supply line (1.5") cross area (which ours did).
I don't want this to get arguementative, since I hate nothing worse that threads going that way. However, just how would the backpressure increase by running MY panels in series, I'm not reducing my pipe diameter anywhere along the route (except the return valve, but that is standard for all systems, so really, that's where my increase in backpressure would come from).
I'd have to say in your setup's case, you've obviously proven that the panels are restriciting your flow - thus the 6gpm vs 12gpm output (and likely creating backpressure) - maybe the cross sectional area of the channels in your panels do NOT equal the cross sectional area of your supply piping, has anyone calculated that at all? If that's the case, then yes, run them in parallel to keep the same flow rate as if they were not in the picture, however, if one panel has the same cross sectional area it should not reduce your flow rate.
if I were to parallel my panels I'd be efectively increasing my pipe diameter and possibly incur the issues that can potentially go unnoticed as I mentioned in my earlier post, running my panels in series allows me to catch anything almost immedialtely...at worst after a backwash cycle.
Obviously, differences in equipment and manufacturers have different outcomes, and if sungrabber recommends it, tehy're probably right - they designed it, our panel manufacturer obviously has different panels.

I agree with you, we don't want to get argumentative, we just want to debate facts and learn from what each other is doing.

When you have many small tubes that equal the same cross sectional area of a larger pipe you do increase resistance to flow. 100 small pipes with cross sectional area of "X" is not equivalent to one large pipe with cross sectional area of "X". That is because there is much more surface are in all those small pipes and you end up with laminar flow at the walls of all those tubes.

Now the difference may also be in that I am running just a small slip stream of the total system flow through the panels and am not trying to run the entire pool flow through them. But that aside, you will always have less pressure drop in a parallel system than a series system. BUT bottom line, if your setup works well for you that is great. I would like if you could post a picture or schematic of it similar to the manual I posted so I could get a better idea of how yours is set up.

Thanks