solar pool water heating panels: parallel versus series configurations

dzerres

New member
Nov 2, 2019
1
Palm Springs, CA
I'm finding some discussions and one scientific paper about installing panels in parallel vs in series and everyone seems to answer, "it depends". There's got to be a general rule-of-thumb for say Southern desert California. or Arizona - just based on experience, no calculus or vapor dome calculations, please. I know if I would install 100 panels, putting them all in series ,the last 20 or so wouldn't gain any additional heat and the backpressure and water volume losses would be huge. The other (all or nothing) option is all in parallel. There the pressure and volume loss problem are eliminated but the water wouldn't have time or distance to pick up much extra heat. So I know the real world answer is some combination of parallel series of panels. I'm installing 16 large panels (4x12): how many runs (panels in series) will add the most heat with the best volume return to the pool? I'm thinking 2 runs in series of 8 panels but maybe 4 runs of 4 panels each would be best. You'd think the dealer or the manufacturer would have these answer but you'd be WRONG.
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
12,874
Pleasanton, CA
Welcome to the forum!

The other (all or nothing) option is all in parallel. There the pressure and volume loss problem are eliminated but the water wouldn't have time or distance to pick up much extra heat.
Not true! If the panels are the same size, parallel and series will collect the same amount of heat from the sun. However, the heat loss, is where they will differ.

BTU transfer to the pool is most important not panel temperature gain. You are right in that the water will become hotter in the panels when plumbed in series but that is actually opposite of what you want. The hotter the water in the panels, the more heat that is lost to the environment. When plumbed in parallel, the water does not get as hot but flows through the panels faster so more of the heat is transferred to the pool.