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SPECIFICATIONS Magic-Pak: HW/HWC
2-18
SRM-HW/HWC 2/99
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.