Purge from solar shuts down gas heater

When I am recovering the heat in the pool from the major temperature changes we are seeing (2 days 60 degrees and windy followed by weekend at 90 degrees wanting to swim), I try to employ both the solar and gas heater on my pool. The solar comes first.

Last weekend we had a party scheduled and I had to heat the pool 10 degrees in a day. I left the house early to do stuff and turned on the pump and gas heater before I left. My solar control kicked in halfway through the morning. I returned in the late morning and my Sta-Rite heater was not firing and the service light was on. I turned it off and on again and everything worked, but a few hours of valuable gas heating were lost.

I think that the air purge from the solar through the heater caused the pressure switch in the heater to detect no flow and shut the gas off. What can I do to prevent this?

If you have a three way valve controlling the solar, can you adjust the stop to allow some of the water to bypass the solar and keep a small amount of water flowing through the heater. This will also reduce the pressure in the panels and head loss in the system both of which are good things.

Or, if you have a solar controller, put it in "test" or "on" mode. Then it won't turn on and off based on the sensor, it will just stay on. Then, when the sun is off the panels, turn it back to "auto". Just don't forget to turn it back or you'll cool the pool at night!