Honeywell ST9141A1002 User Manual page 4

Setting the Heat Fan Off Delay DIP Switches
Set the heat fan off delay DIP switches to 60, 100, 140 or
180 seconds as shown in Fig. 3. The off delay is factory-set
at 140 seconds. This delay time starts when the main gas
valve is de-energized at the end of a thermostat call for heat.
Assure the system operates properly by operating the
system through at least one complete heating cycle and
cooling cycle. Troubleshoot by checking for appropriate
voltages at the ST9141A1002 terminals controlling the
combustion air blower and heat and cool speed circulating
fan. The ST9141A1002 schematic shows internal switch-
ing to clarify operation and assist in troubleshooting. See
Fig. 2.
ST9141A1002 Operating Sequence
Action
Thermostat calls for heat.
(W terminal is energized.)
Thermostat ends call for heat.
(W terminal is de-energized.)
Thermostat begins call for cool.
(G and Y terminals are energized.)
Thermostat ends call for cool.
(G and Y terminals are de-energized.) • Circulating fan turns off after cool fan off delay timing.
Thermostat begins call for fan.
(G terminal is energized.)
Thermostat ends call for fan.
(G terminal is de-energized.)
Primary limit switch string opens.
Checkout
System Response
• Pressure switch confirmed in no airflow position. (If pressure switch shows
airflow, LED flashes three times.)
• Combustion air blower is energized.
• Air proving switch makes (air flow is established).
• Ignition system is energized.
• Gas valve opens and main burner lights.
• Heat fan on delay timing begins. When timing is complete, circulating blower
is energized at heat speed.
• Ignition system is de-energized and gas valve closes.
• Combustion air blower is de-energized after postpurge timing.
• Heat fan off delay timing begins. When timing is complete, the circulating fan
is de-energized.
• Cooling contactor is energized.
• Circulating fan is energized at cool speed after cool fan on delay timing.
• Cooling contactor is de-energized.
• Circulating fan is energized at heat speed two seconds after G terminal is
energized.
• If a call for heat occurs, circulating fan continues to run at heat speed.
• If a call for cool occurs, circulating fan switches to cool speed after four-
second delay.
• Circulating fan is de-energized.
• Thermostat and ignition system are de-energized and gas valve closes.
• Combustion air blower is de-energized.
• Circulating fan is energized at heat speed.
• LED flashes twice.
• If there is a call for cooling or fan, the circulating fan switches from heat speed
to cool speed.
4
Fig. 3—Setting delay off DIP switches.
ST9141
3 DI
EAC N
1 2 HUM
Z1
Z2
DELAY
SPEED
1 2
UP
C
OFF
1 2 1 2
60 SECONDS 100 SECONDS 140 SECONDS
DELAY OFF DIP SWITCH SETTINGS
2
1 3 4
N
NEUTRAL C X X
CIR BLWR
N
Y
G
C Y R
W
1 2 1 2
180 SECONDS
(continued)
ON
OFF
M5658