Fan Manager
A fan manager is used in compressor-operated air-conditioning systems and heat-pump systems to enable the blower to continue running for a short time after the compressor has shut off (see Figure 6-8). This short delay increases the cooling efficiency of the system by allowing the blower enough time to force the residual cooled air into the living spaces. Heat-pump systems can be wired so that the blower shutoff delay also occurs in the heating cycle.
Fan Timer Switch
A fan timer switch is a device that provides timed fan operation for forced warm-air furnaces and unit heaters when they are wired in parallel with a furnace or heater controller. The switch operation is
independent of furnace plenum temperature changes. This factor ensures fan operation and eliminates unnecessary recycling at the beginning and end of burner operation. The use of a fan switch is particularly recommended for horizontal and downflow furnaces.
The Honeywell S876 fan timer switch shown in Figure 6-9 contains a heater-actuated SPST bimetal snap-action switch that turns the fan on after the burner starts and off after the burner stops. Typical wiring connections for a timer switch are shown in Figures 6-10 and 6-11.