Installed new solar panels and problem with sucking air

[dhulls]

I installed 8 HiTemp solar panels from South Africa. I have them set up in 2 separate banks of 4 panels.
The intake line goes to the roof, and then I have the vacuum breaker, and then it "T's" off to the different sets of panels. The lower of the two panels seem to work great with no problems at all. On the upper panels (About 5 feet higher) I am having some minor issues. The panels feel cool to the touch so they do appear to be working but I seem to be getting air into the system. If I remove one the the small lines off of one of the panels I am getting a vacuum instead of water pressure coming out. On the lower set of panels if I remove one of the smaller lines water comes out like you would expect. The return for both the lower and upper set join at the highest point in the system.

My main question is why would I get a vacuum on the panel manifold when removing one of the small lines? Any advice would be helpful.

65,000 Liter pool
.75 HP pump
Aprox 100' run to solar panels

 

[Bama Rambler]

I'm having a hard time picturing your setup. A diagram or pictures would help.

It sounds like your vacuum breaker is in the wrong place and is sucking in air. The return to the pool will cause some vacuum in the panels depending on how it's plumbed. You could try restricting the return flow by partially closing a valve or installing a smaller eyeball in the return fitting to see if it stopped the air from getting in the system.