Installation / Operation Instruction Manual

39
SECTION XI: SERVICE AND TROUBLESHOOTING GUIDE
Sequence of Operations
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, circulator turns on and damper opens.
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. When 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. 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.
5. 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.
6. If for some reason, the tank temperature should exceed 200°F (93°C), than 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.