Air in return with rooftop solar

[bakerj7]

If have rooftop solar, and in-floor cleaning. When the rooftop solar is active, every time the distributor ("5-port actual valve") rotates to a new set of heads there is air in the return from the solar, it blows out from a jet for bit, then no more air. Until the distributor rotates to the next set of heads.
Also, when rooftop solar is active the pressure at the distributor drops from about 14 psi to 2.5 psi. The pressure at the sand filter remains at about 14.

In the first pic you can see the check valve (with window) on the rooftop solar return, just left of the gas heater. Every two minutes, as the distributor moves to a new set, this window fills with a flurry of bubbles for about 10 seconds.

 

[ajw22]

What problems is this causing?

How long has this been the behavior?

 

[bakerj7]

It is not causing any significant problems right now, so far as I know. It has been happening ever since rooftop solar was installed last year. But, we were not using it for a few months.
I have two concerns - one, is it the start of a larger problem? $100 fix turns into $1000 if I ignore it? Two - if it's a bad release valve in the rooftop solar I want it replaced while under warranty.
I've put a call to the installer, and haven't heard back yet. I thought I'd post here also because there's so much more knowledge here than any one pool tech can provide.

 

[ajw22]

Let's see if @proavia can figure out the interaction between your solar and IFCS systems.

I think the air bubbles are expected if the only way for air to get out of your panels is through the IFCS pop ups. Your solar VRV will take in air every time your solar valve cycles.

 

[proavia]

Any air in the system will exit thru the returns - whether those are in-wall returns or the IFCS popups.

I am not familiar with solar panel setups and how they may affect the IFCS. I do know they are supposed to drain when the solar valve closes or the pump shuts off. The VRV is what allows the panels to drain by allowing air to enter the panels when the panels are no longer under water pressure.

I wonder if - when the IFCS water distribution valve cycles thru zones - the pressure/flow to the panels is insufficient and the VRV opens (allowing air in) for a short time. I'm basing this on the pressure change you are seeing at the IFCS water valve.

Does your pool have separate returns you can switch to to see if the issues goes away while using regular returns?
If no separate returns, can you run in spa mode with the solar active?

What RPM is the pump running at when you notice the issue?

 

[bakerj7]

It has wall returns, same thing. Still get air out in a burst every time actuator cycles. I've done every problem isolation conceivable, and it comes down to the solar system. It doesn't matter where else water comes in or goes out, what other valves are open/closed. If it goes through solar, there are bubbles.

You are correct about the pressure being a problem. When the actuator is rotating to a new set the pressure drops to close to 0. Then a burst of bubbles. Then it goes back up to about 2-3psi.

But, what is causing the pressure to be so low when solar is active?

The pump is running at 2500 psi. Default speed is 2000. These have been optimized based on calculations of energy efficiency and water flow. I.e. lowest $/gpm, rotate all heads at least once per day, and circulate all water at least once a day, and sufficient to operate the heads. Except when solar is active.

I could crank it up, but maybe that's a patch, not a solution.