23
FIGURE 23
ST-A1125-13
B. Call For Second Stage, After First Stage Established; Starting from A.11:
1. If a call for second stage (high fire) is initiated after a call for first stage heat is estab
-
lished, the control energizes the W2 inducer assures the high-fire pressure switch is
closed and energizes the second stage of the gas valve.
2. Control enters normal operating loop where all inputs are continuously checked.
C.
Second Stage Satisfied; First Stage Still Called For; Starting From B.2:
1. Once the call for second stage is satisfied, the control starts a 30 second off delay on
W2 inducer and reduces the gas valve to first stage.
2. Control enters normal operating loop where all inputs are continuously checked.
D.
First Stage Satisfied:
1. Zone thermostat is satisfied.
2. Control de-energizes gas valve.
3. Control senses loss of flame.
4. Control initiates 5 second inducer postpurge and 90 second indoor blower delay off.
5. Control de-energizes inducer blower.
6. Control de-energizes indoor blower.
7. Control in the stand by mode with solid red LED.
E. First Stage and Second Stage Called Simultaneously:
1. Zone thermostat contacts close, a call for first stage (low fire) and second stage (high
fire) heat is initiated.
2. Control runs self check.
3. Control checks the high-limit switch for normally closed contacts, each pressure switch
for normally open contacts, and all flame rollout switches for continuity.
4. Control energizes each low-fire inducer.
5. Control checks each pressure switch for closure.
6. If each low-fire pressure switch is closed, the control starts a 30 second prepurge. If
either switch is still open after 180 seconds, the high-fire inducers will be energized until
closure.
7. After prepurge timeout, control initiates spark for 2 seconds minimum, 7 second maxi-
mum ignition trial, and initiates 45 second second stage warm up timing.
8. Control detects flame, de-energizes spark and starts a 45 second indoor blower delay
on timing.
9. After a fixed 45 seconds indoor blower delay on, the control energizes the indoor blow
-
er.
10. After the 45 seconds second stage warmup period control checks the thermostat input.
If W1 and W2 is present control enters normal operating loop where all inputs are con-
tinuously checked.
F. First Stage and Second Stage Removed Simultaneously:
1. Upon a loss of W1 and W2 the gas valve is de-energized.
2. Upon a loss of flame, each inducer will complete a 5 second postpurge and the indoor
blower will complete a 90 second delay off.
3. Control in the stand by mode with solid red LED.
The integrated control is a four-ignition system.
After a total of four cycles without sensing main burner flame, the system goes into a 100%
lockout mode. After one hour, the ignition control repeats the prepurge and ignition cycles
for 4 tries and then go into 100% lockout mode again. It continues this sequence of cycles
and lockout each hour until ignition is successful or power is interrupted. During the lockout
mode, neither the ignitor or gas valve will be energized until the system is reset by turning
