What is the difference between circ and auto settings for the fan on my HVAC thermostat when the heat is on, when the a/c is on, and when both of those are off?
I know that “on” turns the fan on so that it runs continuously whether the heat is on, the a/c, or nothing is on.
My older thermostat only had on and auto, and I can’t figure out what circ is for. Clearly, it means “circulate” or “circulation,” but what does that mean?