16
OPERATING SEQUENCE
The operating sequences for the heating, cooling, and
fan modes are described below. Refer to the wiring
diagrams (Figures 15 - 19, pages 37 - 41).
Cooling Mode:
1. On a call for cooling the thermostat closes, applying
24 VAC to “Y1”, “G”, and “Y2” if Stage 2 cooling is
calling.
2. “G” applies 24VAC to the main circulating blower
circuit.
3. “Y1” and “Y2” apply 24VAC through all safety switches
before energizing their respective contactors.
4. When the thermostat is satisfi ed the contactors are
de-energized.
5. The circulating blower motor de-energizes
immediately.
Heating Mode for 200 & 235 kBtuh Heat
Exchangers:
1. On a call for heat, the thermostat closes, applying 24
VAC to the “W1” terminal (and “W2” terminal if Stage 2
heat is required).
NOTE:
There is a three minute time
delay before Stage 2 heat is energized.
2. The integrated control monitors the safety circuit at all
times. If either the roll-out switch or the over-temperature
limit controls open, the gas valve will not energize.
The main blower continues to operate until the over-
temperature limits close, the fl ame roll-out switch is
manually reset, or the thermostat is satisfi ed.
3. The integrated control checks all safety switches at
the beginning of each heating cycle. If closed, the
combustion blower performs a 15 second pre-purge.
4. The integrated control will then supply power to the
direct spark ignitor and immediately energizes the gas
valve.
5. The fl ame must be proven through the fl ame sensor in
7 seconds to hold the gas valve open. The integrated
control will monitor the gas fl ame with the fl ame sensor
for the entire time the gas valve is open. If for any reason
the gas fl ame drops out, the gas valve will immediately
close. After 30 second purge, the integrated control will
try to ignite two more times.
6. The main air blower will start and continue to run 45
seconds after the gas valve opens.
7. When the thermostat is satisfi ed, the integrated control
is de-energized. The gas valve and combustion blower
de-energize immediately while the main air blower
continues to run through the blower off delay of 150
seconds.
8. If the unit fails to prove fl ame after three ignition attempts,
it will go into a soft lockout. The unit will re-attempt the
start-up procedure every hour until the thermostat is
satisfi ed or 24 VAC power is removed from the unit for
a minimum period of 5 seconds.
Heating Mode for 100 & 166 kBtuh Heat
Exchangers:
1. On a call for heat, the thermostat closes, applying 24
VAC to the
W1
terminal (and
W2
terminal if Stage 2
heat is required).
2. The integrated control monitors the safety circuit at all
times. If either the roll-out switch or the over-temperature
limit controls open, the gas valve will not energize.
The main blower continues to operate until the over-
temperature limits close, the fl ame roll-out switch is
manually reset, or the thermostat is satisfi ed.
3. The integrated control checks all safety switches at
the beginning of each heating cycle. If closed, the
combustion blower performs a 10 second pre-purge.
4. The integrated control will then supply power to the
direct spark ignitor and immediately energizes the gas
valve.
NOTE:
Burner operation begins in high fi re mode
with both Stage 1 and Stage 2 gas valve energized,
independent of the thermostat call for Stage 2 heat.
If after 30 seconds of operation with no call for Stage
2 heat, the integrated control will resume heating
operation in low fi re mode of operation and Stage 2
gas valve is de-energized.
5. The fl ame must be proven through the fl ame sensor in
10 seconds to hold the gas valve open. The integrated
control will monitor the gas fl ame with the fl ame sensor
for the entire time the gas valve is open. If for any reason
the gas fl ame drops out, the gas valve will immediately
close. After 30 second purge, the integrated control will
try to ignite fourteen more times.
6. The main air blower will start and continue to run 40
seconds after the gas valve opens.
7. When the thermostat is satisfi ed, the integrated
control is de-energized. The gas valve and combustion
blower de-energize immediately while the main air
blower continues to run through the blower off delay
of approximately 150 seconds.
8. If the unit fails to prove fl ame after fi fteen ignition
attempts, it will go into a soft lockout. The unit will
re-attempt the start-up procedure every hour until the
thermostat is satisfi ed or 24 VAC power is removed
from the unit for a minimum period of 5 seconds.
NOTE:
See Table 2 (page 17) or Figure 15 (page 37)
for a complete list of heating operation fault codes.
Blower Mode:
1. On a call for fan operation, the thermostat applies 24
VAC directly to the blower contactor.
2. The circulating blower is energized immediately.
