Thermo Pride CHX3-75N Installation And Operation Manual page 57

All installations and services must be performed by qualified service personnel.
IS INDUCER RUNNING
ON LOW SPEED?
YES
DOES THE HOT
SURFACE IGNITOR
ENERGIZE AND GLOW?
YES
AFTER HOT SURFACE
IGNITOR WARM-UP,
DOES GAS VALVE OPEN?
YES
AFTER GAS VALVE
OPENS, DO THE
BURNERS IGNITE?
YES
CHECK CONTACTS ON LOW
FIRE PRESSURE SWITCH
NO
AND FOR BLOCKAGE IN FLUE.
IF OK, REPLACE DUAL
PRESSURE SWITCH.
IS THERE VOLTAGE ACROSS
HOT SURFACE IGNITOR
NO
TERMINALS "IGN" & "IGN N"
AT THE 50V51-843 CONTROL
AFTER 17 SECOND PREPURGE?
YES
CHECK WIRING TO HOT
SURFACE IGNITOR AND
IF OK, REPLACE HOT
SURFACE IGNITOR
ASSEMBLY
CHECK ACROSS "MVL" AND
"MV COM" TERMINALS ON
50V51-843 CONTROL FOR 24
NO
VOLTS DURING THE 4 SECOND
FLAME PROVING PERIOD
AFTER IGNITOR WARM-UP.
IS THERE 24 VOLTS?
YES
IS COLLECTOR BOX
PRESSURE SWITCH CLOSED?
YES
CHECK WIRING TO GAS
VALVE AND IF OK,
REPLACE GAS VALVE.
CHECK FOR PROPER LINE
NO AND MANIFOLD PRESSURE.
REFERENCE GAS PRESSURE
CHART PAGE 31.
51
NO
NO
NO
OK
REPLACE THE
50V51-843 CONTROL.
YES
IS THE HIGH LIMIT,
ROLL-OUT LIMIT, AND
AUX LIMIT ON
(CDX MODELS)
SWITCHES CLOSED?
NO
IF HIGH LIMIT OR
AUX LIMIT OPEN CHECK
FOR RESTRICTED
FILTERS OR DUCT WORK
IF ROLL-OUT SWITCH
OPEN INSPECT FLUE FOR
RESTRICTIONS.
REPLACE THE
50V51-843 CONTROL.
CHECK DRAIN FOR
BLOCKAGE WATER
TRAPPED IN HOSE,
REPLACE SWITCH.