First, will I damage my oil furnace if I manually turn the fan on and then the thermostat calls for heat? In normal operation the fan turns on from a temperature switch inside the air handler above the furnace burner (honeywell Tyle L498). My concern is if the fan is running, then the thermostat calls for heat, the oil burner will have trouble firing and then heating up because the fan is already running.
If doing this won't damage furnace.
Second question is can I just wire the "G" and "Rc" terminals on thermostat to an ice cube relay (24v ac in to relay). Then wire the ice cube relays 120v contacts in between the the 120v line in side screw and "fan on" screw on the honeywell L498 fan controller?