SECTION XI: DIAGNOSTIC AND TROUBLESHOOTING GUIDE
LOW FIRE START CONTROL SYSTEM WITH DIRECT SPARK IGNITION
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 15 second pre-purge period. The combustion blower runs at full speed during this period
to purge the combustion chamber of any unburned gases.
2. The blower speed decreases to the reduced light-off rate speed. Once this reduced speed has stabilized, the
control is ready to start the trial for ignition period to light the burner.
3. After the light-off speed on the combustion blower has stabilized, the control sends high voltage through the spark
cable to the spark rod to spark to the burner and the gas valve also opens.
4. After the burner lights, a microamp current is generated through the flame sense rod allowing the control to detect
burner flame.
5. 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.
6. After the burner ignites, the blower remains at the reduced light-off rate speed for 10 seconds to allow the flame to
stabilize. After this period, the combustion blower will gradually increase to full speed to allow full input to the
burner.
7. If the burner fails to light, the gas valve closes, sparking to the burner stops, and the combustion blower increases
to full pre-purge speed for 15 seconds to purge the heat exchanger of unburned gas.
8. The blower reduces to light-off rate speed and the trial for ignition is repeated. The control will make 3 retries to
ignite the burner. If the burner fails to light after the third retry, the control enters a Hold period which is an idle
period for 15 minutes.
9. There will be a flashing code 110 alternating with the DHW tank temperature 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 4 ignition attempts after the 15 minute waiting period.
10. 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 post-purge for 30 seconds and
then stop. A lockout code 67 (“ILK” is a string of safety switches) will be displayed on the water heater display.
11. When the blockage is removed, the control can be reset by pressing the lower left button under “Reset”.
12. The burner flame is monitored by the flame sense circuit. If the flame should extinguish, the gas valve closes, and
the combustion blower will operate at full speed to purge the heat exchanger before making an attempt to relight
the burner. There may be up to 4 attempts to light the burner before going into the 15 minute ignition hold period
explained previously.
13. The burner will continue to operate during the heating cycle until the thermostat satisfies. The gas valve closes,
and the combustion blower continues to operate for 30 seconds to purge the heat exchanger of flue gases.
14. If the tank temperature exceeds 200°F (
93°C
), the control closes the gas valve and goes into a “Lockout” state
and will not operate until reset by a qualified service person. The display will read lockout code “79”, 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.
15. Refer to the diagnostic service section at the end of this Installation and Operation Manual.
ACCESSING DIAGNOSTIC MODE ON THE WATER HEATER DISPLAY (FOR SERVICE PERSONNEL ONLY)
The display has a “Diagnostic Mode” for accessing information in aiding servicing of the water heater. This procedure is
for service and installation personnel only. To enter the Diagnostic Mode, follow the steps illustrated below:
WARNING
The following procedure is for service and installation personnel only. Resetting lockout conditions
without correcting the malfunction can result in a hazardous condition.
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Содержание 120T400
Страница 38: ...LIGHTING AND SHUT DOWN INSTRUCTIONS Figure 26 Lighting Instruction Label 38...
Страница 59: ...NOTES 59...
