I have a solar heater and gas heater here in the Pacific NW where I need to use my gas heater often just to keep my pool comfortable enough to swim. Right now my Jandy controller will only allow solar heat OR gas heat but not both at the same time. I'm tempted to put an external Solar controller like the Hayward GL-235 on that 3 way valve to turn on the solar panel when it has enough heat to preheat the water going into my gas heater.
I figure I might as well get the heat out of my solar and then into the gas heater. Is there a reason the Jandy won't allow this? Am I missing something? Thank you.