Many of you may remember I could have been happier with my solar heating installation. It now has 4 panels on a low roof plumbed in series with 10 panels on a high roof. The 4 lower panels (that ALL the water has to go through) cause quite a resitriction and either make the pump work very hard or makes the water flow too slow to get good heating (maybe 2 gpm/panel in the upper panels).
The solar installer swore that while the manufacturer recommended parallel plumbing for this situation that they have found that it works better in series. I think they were lazy/cheap.
Either way -- for this year I want to add 4 more east-facing panels (no more south roof available and I figure this will get the heating going in the morning when it's needed) to the lower circuit and have it re-plumbed to be in PARALLEL with the upper bank of panels.
The question is about the correct way to plumb parallel banks at different levels:
- split the two with a manual valve and adjust until the panels get the same flow.
- run the return for the lower bank all the way up to the upper bank and then tie in the upper bank there (instead of separate returns)
The solar install guy says the second method is best as the valve will add back pressure. I figure the elevated reutrn will add the same amount of back pressure -- the end effect is to cripple the lower bank enough to get the flows the same -- no mater how it's done.
Will the second method result in equal flows?
The solar install guy uses a temperature gun to check if the flows are the same between panels (cool idea).