Honeywell RTHL2310 series

Set fan operation switch
Move the switch to the proper setting:
Gas or Oil: For gas or oil heating systems, leave the fan operation switch in this factory-set position (for systems
that control the fan in a call for heat).
Electric or Heat Pump: Change the switch to this setting for heat pump or electric heat systems. (This setting is
for systems that allow the thermostat to control the fan in a call for heat, if a fan wire is connected to the G
terminal.)