Armstrong World Industries 122, 243 Simplified Sequence - HW w/Fenwal 05-29 Board, Call For Heat

Service Reference Manual SEQUENCE OF OPERATIONS

2-33

Simplified Sequence - HW (w/Fenwal 05-29 Board)

Refer to Figure 2-6

CALL FOR HEAT

1.The indoor thermostat calls for heat by energizing the R-W circuit.

2.This sends a 24-volt signal to the ignition control, causing the induced draft blower to run.

3.A 24-volt signal is also sent to the blower control board at this time, starting a 60-second circulating air blower “on” delay. The circulating air blower starts 60 seconds after the initial call for heat.

4.The induced draft blower causes the pressure switch to close which starts a 30-second pre-purge. After the pre-purge period, the burners ignite.

5.The unit operates in the heating mode until the indoor thermostat setting is reached and the R-W circuit is interrupted.

6.When the R-W circuit is interrupted, the 24-volt signal to the ignition control and the signal to the blower control board are interrupted.

7.The induced draft blower stops within several seconds and a 90-second circulating air blower “off” delay starts. Following the delay period, the circu- lating air blower shuts off.

SRM-HW/HWC 2/99

Detailed Sequence follows