Solar panel installation question

[cleancloths]

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.

[matt4x4]

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.).

[cleancloths]

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?

[matt4x4]

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.

[cleancloths]

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.

[matt4x4]

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.

[cleancloths]

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