Armstrong World Industries 122, 243, 302, 242, 123, 203, 182 Call For Heat, Call For Cooling, Fan On

Service Reference Manual SEQUENCE OF OPERATIONS

2-17

Simplified Sequence - HWC122,182, 242, 302 (w/Fenwal Triton 2461D DSI Ignition Control)

Refer to Figure 2-3

CALL FOR HEAT

1.A call for heat closes the circuit between wires R (red) and W (white) on the unit’s thermostat connec- tions.

2.A low voltage (24 volts) signal is sent to the ignition control, closing a relay which sends line voltage to the induced draft blower. At the same time, a 24- volt signal is also sent to the blower control board. This causes the blower control board to begin the countdown to closing the relay that starts the circulating air blower.

3.After the induced draft blower creates enough negative pressure, the pressure switch closes.

4.When the pressure switch closes, the 24-volt signal is sent to the ignition control. This starts a 30- second pre-purge countdown, after which a trial for ignition is made.

5.At the same time that the trial for ignition is made, the gas valve energizes and gas flows to the burners.

6.With the burners in operation, the trial for ignition continues for seven seconds. At the end of this time, the ignition control stops sparking.

7.Approximately 30 seconds after the burners ignite, the timer on the blower control board closes a relay, sending line voltage to and starting the circulating air blower.

8.The unit continues to operate as long as there is a 24-volt signal between R and W. When the call for heat is satisfied, the 24-volt signal between R and W discontinues. When W de-energizes, the power to the induced draft blower and the gas valve is interrupted. The 24-volt signal to the blower control board is also interrupted, causing the module to start the countdown to blower “off” (approximately 90 seconds).

9.If at any time during a call for heat the limit switch opens, the 24-volt signal to the white wire going to terminal P.SW on the ignition control is interrupted. This de-energizes the gas valve immediately. The circulating air blower and the induced draft blower continue to run. When the unit cools down enough for the limit switch to close, the 24-volt signal is again sent to the P.SW terminal on the ignition control. With terminal P.SW energized, the ignition control again makes a trial for ignition and relights the burners.

CALL FOR COOLING

1.A call for cooling closes the circuit from R to Y and G.

2.A 24-volt signal is sent to blower control board terminal G and to the compressor contactor. The contactor closes, sending line voltage to the com- pressor and the outdoor condenser fan.

3.With a 24-volt signal at terminal G on the blower control board, the circulating air blower starts in cooling speed approximately 15 seconds later (or immediately - see note below).

4.When the cooling call is completed, G and Y de- energize. The contactor opens immediately, stop- ping the compressor and the outdoor cooling fan. When G de-energizes, the timer to turn off the circulating air blower starts. The circulating air blower turns off after 90 seconds (see note below).

FAN ON

1.When the thermostat switch is moved to the “FAN ON” position, the circuit between R and G closes.

2.The 24-volt signal from G goes to the blower control board which starts the timer.

3.Fifteen seconds after terminal G on the blower control board energizes (or immediately after - see note below), the circulating air blower starts.

4.When terminal G on the blower control board de- energizes, the timer to turn off the circulating air blower starts. The circulating air blower turns off after 90 seconds (see note below).

Note: Heatcraft blower control boards have a G “on” delay of 15 seconds and an “off” delay of 90 seconds. Tridelta blower control boards have no “on” time delay and a 60 -130 second “off” delay.

SRM-HW/HWC 2/99

Detailed Sequence follows