Armstrong World Industries HWC PREMIER 183 - Manual (Page 19)

Service Reference Manual SEQUENCE OF OPERATIONS
2-9
SRM-HW/HWC 2/99
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-G circuit 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-G circuit.
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.