Sears 9MPD Furnace User Manual


 
HONEYWELL SV9541M "SMART VALVE" Sequence of Operation
IPOWERAPPLIEDTO APPLIANCE
+
I THERMOSTATCALLS FORHEAT
¢
IPRESSURE SWITCHES PROVED OPEN?
ICOMBUSTIONBLOWER ENERGIZED
PRESSURESWITCHESCLOSEDWITHIN30SEC-
ONDS?
+
I 3SECONDPRE-PURGE
PILOTVALVEOPENS:
IGNITORPOWERED(1)
PILOTLIGHTSAND FLAME ISSENSED l'_Vl
DURING90SECOND TRAILFOR
IGNITION?
I YES
MAINVALVEOPENS,
HEATINGFAN"ON" DELAYBEGINS
+
I AFTERDELAY:CIRCULATINGBLOWERSTARTS I
YES
FLAME SENSE LOST? I I
THERMOSTATCALL FORHEAT ENDS
NO
PILOTAND MAINVALVECLOSE
+
COMBUSTIONBLOWERDE- ENERGIZEDAFTER 30
SECONDPOST PURGE
+
I CIRCULATINGBLOWEROFFAFTERDELAY
I
I WAITFORNEXTCALL FOR HEAT
I
I
WAIT FORPRESSURESWITCHESTOOPEN
_._ COMBUSTIONBLOWERDE-ENERGIZED
J__ FIVEMINUTEWAITPERIOD
I
THREESECONDFLAME ,J_
FAILURERECYCLEDELAY
PILOTVALVECLOSES;
PILOTIGNITOROFF
PILOTAND MAINVALVECLOSE 1
L FLAMESENSELOSTMORETHAN FIVETIMESINTHIS CALL FORHEAT?
NO
YES
r
CIRCULATINGBLOWEROFFAFTERDELAY
+
COMBUSTIONAIRBLOWEROFFAFTERPOST
PURGE
I
(1) Ignitor "ON" for first 30 seconds of trial for ignition, then "OFF" for next 30 seconds. Ifthe 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 I hour wait
period.
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