Armstrong World Industries 243, 302 POWER Line Voltage, L1 Power, L2 Power, Low Voltage 24 VAC

SPECIFICATIONS Magic-Pak: HW/HWC

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Detailed Sequence - HWC123, 183, 243, 303

Refer to Figure 2-1

POWER

Line Voltage

With the unit at rest (no call from the thermostat), line voltage will be present:

L1 Power

1.Through the L1 black lead to the L1 terminal on the ignition control

2.At the L1 contactor terminal

3.At the transformer terminal marked 208-240V

L2 Power

1.Through the L2 black lead to the induced draft blower

2.At the L2 contactor terminal

3.A transformer common terminal

4.At the T2 contactor terminal

5.At the R terminal of the compressor

6.At the capacitor common terminals

Low Voltage (24 VAC)

With the unit at rest (no call from the thermostat), 24 volts A/C will be present:

1.From the transformer 24V terminal to pin 4 of the 6-pin chassis low voltage harness

2.From pin 4 of the chassis low voltage harness to the

24VAC hot terminal on the ignition control

3.From the 24VAC hot terminal to pin 5 of the 5-pin thermostat harness (internal to board)

4.From the 24VAC hot terminal also to pin 6 of the 6- pin ignition wire harness

5.From pin 6 of the ignition wire harness through the auto reset limit switch and the manual reset rollout switch to pin 1 of the 6-pin ignition wire harness

Note: While the unit is at rest, the green LED shows consistent slow flash. This indicates normal operation - system at rest (standby mode).

CALL FOR HEAT

Line Voltage

The ignition control receives a signal from the R-Wcircuit indicating a call for heat.

1.The combustion blower relay energizes, sending L1 power to CMB BLWR terminal on the ignition

control. This causes the combustion blower to start by completing the line voltage circuit through the L2 wire connection in the unit.

2.As the 24-volt signal is sent to pin 4 of the 6-pin ignition wire harness by the ignition control, a 30- second circulating air blower “on” delay starts. After the delay, the ignition control energizes the heat speed blower relay. This sends L1 power to the

ACB HEAT terminal on the ignition control.

3.L1 power is then sent to the circulating air blower terminal block where it is connected to the blower motor. The circulating air blower starts by completing the L1-L2 circuit through the L2 connec- tion at the blower motor capacitor.

4.The combustion blower and the circulating air blower continue to run until the R-W circuit is interrupted. After a 5-secondpost-purge delay, the

CMB BLWR terminal on the ignition control de- energizes. This interrupts L1 power to the combus- tion blower. After a 120-secondcirculating air blower “off” delay, the ACB HEAT terminal de- energizes. This interrupts L1 to the circulating air blower. As L1 power is interrupted, the blowers shut off.

Low Voltage

1.A call for heat closes the R-Wcircuit, sending a 24- volt signal to the low voltage white wire in the unit.

2.The 24-volt signal is received at pin 3 of the 5-pin thermostat harness on the ignition control.

3.The 24-volt signal causes the combustion blower relay to close, causing the combustion blower to run. At this time, a 24-volt signal is also sent out through pin 2 of the 6-pin ignition wire harness.

4.The 24-volt signal from pin 2 of the 6-pin ignition wire harness energizes one side of the Normally Open pressure switch. As the induced draft blower reaches full speed, the pressure switch closes and a 24-volt signal is sent to pin 5 of the 6- pin ignition wire harness.

5.When the 24-volt signal is received at pin 5 of the 6- pin ignition wire harness, the ignition control starts a 30-second pre-purge delay.

6.After the 30-second pre-purge, the ignition control initiates a trial for ignition. The spark ignition cable terminal and pin 4 of the 6-pin ignition wire harness energize simultaneously.

7.When the 24-volt signal is present at pin 4 of the 6- pin ignition wire harness, the ignition control starts a 30-second circulating air blower “on” delay.

8.The 24-volt signal from pin 4 of the 6-pin ignition wire harness is received at the gas valve, causing it to open and the burners to ignite.

SRM-HW/HWC

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