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SECTION XI: DIAGNOSTIC AND TROUBLESHOOTING GUIDE
DIRECT SPARK HONEYWELL INTEGRATED CONTROL SYSTEM
SEQUENCE OF OPERATION
1. When the tank temperature drops below the temperature setpoint on the display, the control sends power to the
combustion blower for a 30 second pre-purge period.
2. At the end of the pre-purge period, the control sends high voltage through the spark cable to the spark rod to spark
to the burner. The gas valve also opens. If the burner lights, a microamp current is generated through the flame
sense rod allowing the control to detect burner flame. The sparking then ceases and the flame is monitored by the
flame sense circuit until the tank temperature reaches the thermostat setpoint and turns off the gas valve.
3. If the burner fails to light, the gas valve closes, sparking to the burner stops, and the combustion blower continues
to operate for 60 seconds to purge the heat exchanger of unburned gas. The ignition trial is repeated. The control
will make 3 attempts to ignite the burner. If the burner fails to light after the third attempt, the control enters “Soft
Lockout”, which is an idle period for 60 minutes. There will be an error code 62 or 63 shown on the water heater
display indicating that the control cycled through the maximum number of ignition retries for ignition. The control will
make another 3 ignition attempts after the 1 hour waiting period.
4. If the exhaust vent terminal should become blocked or the condensate drain becomes plugged, the exhaust vent
pressure switch will open and the gas valve closes. The combustion blower will continue to operate. An error code
29 is shown on the water heater display. Removing the blockage will resume normal operation.
5. The burner flame is monitored by the flame sense circuit and if the flame should extinguish, the gas valve closes
and the combustion blower will operate to purge the heat exchanger before making an attempt to relight the burner.
There may be 3 attempts to relight the burner before going into the Soft Lockout period explained previously.
6. The burner will continue to operate during the heating cycle until the tank temperature reaches the setpoint. The
gas valve opens and the combustion blower continues to operate for 30 seconds to purge the heat exchanger of
flue gases.
7. If for some reason, the tank temperature should exceed 200°F (93°C), then the control closes the gas valve and
goes into a “Hard Lockout” state and will not operate until reset by a qualified service person. The display will read
error code “65”, which indicates the tank high limit temperature has been exceeded. No attempt should be made to
reset the control until a service person has corrected the cause of the high limit condition. Refer to the diagnostic
service section at the end of this Installation and Operating Instruction Manual.