Using pool solar panels of two different sizes

[portkey]

Question: Is there a way to install two different lengths of solar panels where you don't end up with flow problems -- where the water flows through one panel size more than the other size because it is a little shorter run through the riser tubes? If so, what configuration/layout?

Potential options:
1) Single row series as shown in figure 6.1 with a common feed through the bottom in single row and a different return from each set of commonly sized panel feeding into a common return line?
2) Series feed as shown in Figure 6.4 where you feed one set of panels of one size first, then take the return from that set and use that to feed the next set of panels of a different size?
3) Other ideas?

Thank you in advance for your help and guidance on this question. I'm a newbie and my wife really wants to install solar for our pool. I found some very lightly used heliocol panels for a great deal locally however there are two different sizes. Three are 10.5 ft and two are 12.5 ft in length. I'm struggling with trying to figure out if I should go ahead and buy these used panels even though they are two different lengths given it will take some additional work on the install, but the tradeoff is that it would cost me a small fortune to buy three new 12.5ft panels to match the two that I'm getting for a song. I'd rather use the three 10.5 footers along with the 12.5 footers if possible.

From this article, it strongly suggests using an "opposite end (reverse) return" design which looks like the figure below The Flow Imbalance Myth Debunked. This shows all of the panels the same length.


The pictures below from the Heliocol install manual are some suggested layouts. The manual doesn't address how to handle this kind of situation of two different sized panels.
behttps://www.umasolar.com/wp-content/uploads/2018/10/Heliocol-Manual.pdf

 

[mas985]

Welcome to the forum!

I don't think the difference in head loss will result in much of a difference in flow rate. I think manufactures make a bigger deal out of this than it warrants. As long as the head loss in the header is insignificant, which it should be if you are operating at the appropriate flow rate levels for the given area of the panels, then it really shouldn't mater all that much how the panels are plumbed.

If your 4x10 panel has 4 GPM flowing through it, it would have about 0.5' of head loss. When panels are plumbed in parallel, each panel will have approximately the same amount of head loss since the share pressure nodes at both ends of the two headers. This means the 4x12 panel at the same head loss would have a flow rate of 3.65 GPM. Not much different. Conversely, setting the 4x12 to 4.8 GPM (i.e. 0.1 GPM/sq-ft) would result in a flow rate for the smaller panel of 5.25 GPM. Neither is going to make a huge difference. The important thing is to set the minimum flow rate for the larger panels at or above 0.1 GPM/sq-ft to maintain efficiency.

What pump do you have?

How high are the panels installed?

 

[portkey]

Thank you mas985
We have a Pentair Intelliflo 011018 3 hp variable. Nothing has been installed yet. I'm trying to decide between buying some Heliocol panels that are lightly used for $250 and doing the install myself by buying the DIY kit brackets, versus biting the bullet and paying retail for someone else to do it. Your response is helpful because the panels I found for $250 will meet my needs in terms of coverage (50-60% of pool size), but I was concerned about have a mix of two different panel sizes. It sounds like I should be fine.