Solar panel Flow

[launboy]

Now that I've got my solar panels up and running, I have a question...

How do I know how far to close the bypass so the panels have good flow, but don't get too much?

I have a 1 HP Hayward PowerFlo LX pump, which is supposed to put out 60 GPM. I did a test with a five gallon bucket and got 37 GPM with solar off and about 30 GPM with the bypass fully closed. Normal operating PSI is 14, with bypass fully closed, I get 15 PSI.

Thanks,
Adam

 

[mas985]

Only 1 PSI rise when all of the water goes through the panels? That seems very low for only three panels. Anyway if that is correct, then there doesn't seem to be any reason not to have all the water go through the panels unless the manufacture has a recommendation on flow rate per panel that is less than 10 GPM.

 

[amjohn]

I only get 0.5-1 psi (the gage varies from day to day) rise on my panels (2 panels, 4x20 each) with all the flow going through them as well with a 1.5 hp pump. I am going to install a flow meter and a new gage - my gage is junk- but the panels are doing their job. They heat and cool as expected. I think my pump might have a pretty big fudge factor to come up with that 1.5 hp, but even if it is more like 1hp, it seems like I ought to get more than that. I would also be curious to find out if others are seeing the "manufacturers expected" psi increase, or something much less?

 

[launboy]

Well, the Sungrabber panels say they have a max of 4 GPM per panel. This year they are all plumbed in parallel. Last year, 2 panels were plumbed in series, and the third had water going down one end and coming out the same side.(did that make sense) and I always ran with full flow to the panels with no problems. Course, that was with a different pump(still 1 HP) but I only had 10 PSI without solar and 11 with it back then.

Something interesting I noticed is that when I push open my vacuum breaker(1/2" PVC Check valve) which is located at the highest point, on the return side of the panels, that not much water flows out(with bypass closed, all water through panels. The interesting part is that when the bypass is fully opened, more water actually flows out of the check valve.

P.S. If it matters, the panels are on a 1 story high garage roof.

Thanks,
Adam