Armstrong World Industries 122, 243, 302, 242, 123, 203, 182, 183 manual Fan On

Service Reference Manual SEQUENCE OF OPERATIONS

2-9

6.After the 90-second delay, the ignition control de- energizes the cooling speed relay and the circulat- ing air blower stops.

FAN ON

1.When the thermostat is switched to the “FAN ON” position, the R-Gcircuit sends a 24-volt signal to pin 4 of the 5-pin thermostat harness.

2.The 24-volt signal energizes the cooling speed relay, sending L1 power to the ACB COOL terminal of the ignition control.

3.L1 power is sent to the circulating air blower terminal block, causing the circulating air blower to run in cooling speed.

4.The circulating air blower continues to run in cooling speed until the thermostat is switched to “AUTO”, interrupting the R-Gcircuit.

Note: With the thermostat in the “FAN ON” position during heat call, ignition control will not energize the heat speed relay. The circulating air blower continues to run in cooling speed unless the limit switch circuit opens, which would cause the heat speed relay and the induced draft blower relay to become energized. This would de-energize the cooling speed relay until either the limit switch circuit is closed or the thermostat is switched to the “AUTO” position.

SRM-HW/HWC 2/99