Single Stage Multi Position Furnace
Service Manual
46
440 08 2001 02
HONEYWELL SV9541M “SMART VALVE” Sequence of Operation
POWER APPLIED TO APPLIANCE
THERMOSTAT CALLS FOR HEAT
COMBUSTION BLOWER ENERGIZED
PRESSURE SWITCHES CLOSED WITHIN
30 SECONDS?
COMBUSTION BLOWER DE--ENERGIZED
PILOT VALVE OPENS:
IGNITOR POWERED (1)
THREE SECOND FLAME
FAILURE RECYCLE DELAY
3 SECOND PRE--PURGE
FIVE MINUTE WAIT PERIOD
PILOT LIGHTS AND FLAME IS SENSED
DURING 90 SECOND TRAIL FOR
IGNITION?
PILOT VALVE CLOSES;
PILOT IGNITOR OFF
MAIN VALVE OPENS,
HEATING FAN “ON” DELAY BEGINS
AFTER DELAY: CIRCULATING BLOWER
STARTS
FLAME SENSE LOST?
CIRCULATING BLOWER OFF AFTER
DELAY
PILOT AND MAIN VALVE CLOSE
COMBUSTION AIR BLOWER OFF AFTER
POST PURGE
FLAME SENSE LOST MORE THAN FIVE
TIMES IN THIS CALL FOR HEAT?
THERMOSTAT CALL FOR HEAT ENDS
COMBUSTION BLOWER DE--ENERGIZED
AFTER 30 SECOND POST PURGE
PILOT AND MAIN VALVE CLOSE
CIRCULATING BLOWER OFF AFTER
DELAY
WAIT FOR NEXT CALL FOR HEAT
PRESSURE SWITCHES PROVED OPEN?
NO
NO
NO
NO
YES
YES
WAIT FOR PRESSURE SWITCHES TO OPEN
(1) Ignitor “ON” for first 30 seconds of trial for ignition, then “OFF” for next 30 seconds.
If the pilot has not lit, it turns back “ON” for the final 30 seconds. The pilot valve remains
energized during the entire 90 second trial for ignition.
NOTE: If main limit string opens and takes longer than 2 minutes to close, system goes
into 1 hour wait period (indicating circulating blower).
YES
NO