Armstrong World Industries 123 POWER Line Voltage, Second black wire, 2. L-2 on the contactor

SPECIFICATIONS Magic-Pak: HW/HWC

2-18

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

Refer to Figure 2-3

POWER

Line Voltage

When the service disconnect switch is closed, power is sent to the unit (unit in standby, no signal from the thermostat). Power (208 - 230 volts A/C) is supplied to both black wires located in the junction block on top of the unit.

Line voltage will be present at the following locations:

First black wire

1.L-1 on the ignition control

2.L-1 on the contactor

3.L-1 on the blower control board

4.Terminal on the transformer marked 208V or 240V (whichever is being used)

Second black wire

1.Supplies power to the induced draft blower

2.L-2 on the contactor

3.Common terminal on the transformer

4.T-2 on the contactor

5.Red wire on the R terminal of the compressor

6.Red wire to the common terminals on the capaci- tors

Low Voltage (24 VAC)

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

1.Red wire exiting the top of the unit

2.Terminal marked 24 VAC on the ignition control

3.Terminal R on the blower control board

CALL FOR HEAT

Line Voltage

The thermostat closes the circuit between R and W.

The following is the sequence of operation for the line voltage side of the unit:

1.Terminal TH (24-volt) energizes on the ignition control, causing the relay in the ignition control to close. This sends line voltage to the terminal marked IND, causing the induced draft blower to start.

2.When W energizes, a 24-volt signal is also sent to the W terminal on the blower control board. The 24-volt signal to the blower control board starts the timer on the board. After 60 seconds, the heat speed relay on the blower control board closes. This sends line voltage from the terminal marked

HEAT to the circulating air blower, starting the blower. The induced draft blower and the circu- lating air blower continue to operate until the heat call is satisfied, interrupting the circuit between R and W. The W terminal de-energizes, causing the blower relay to open approximately 90 seconds later. This interrupts the line voltage to the circulat- ing air blower and the blower shuts down.

Low Voltage

1.A call for heat closes the circuit in the thermostat between R and W, sending a 24-volt signal to the white wire on the unit.

2.The white wire goes to the C terminal on the limit switch, ignition control terminal TH and terminal W on the blower control board.

3.When W energizes, the timer starts a countdown to blower “on”. The blower starts in approximately 60 seconds.

4.The 24-volt signal sent to terminal TH closes the relay in the ignition control. This starts the induced draft blower by energizing terminal IND on the ignition control.

5.As the induced draft blower comes up to speed and creates enough negative pressure, the pres- sure switch closes. The 24-volt signal from the pressure switch energizes terminal P.SW, causing the ignition control to start a trial for ignition (sparking).

6.As the trial for ignition starts, the V1 terminal on the ignition control energizes. At the same time, a 24- volt signal is sent to the gas valve, opening the valve. The unit continues to operate as long as W is energized.

7.When the call for heat is satisfied, the circuit be- tween R and W is interrupted.

8.With W de-energized, the gas valve closes immedi- ately and the induced draft blower shuts down several seconds later.

9.The blower control board starts a countdown to blower “off”. Approximately 90 seconds later, the blower shuts down.

SRM-HW/HWC

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