State SBL85 390NE A - Manual (Page 18)

16 Servicing should only be performed by a Qualified Service Technician
OPERATION AND SERVICE
SEQUENCE OF OPERATION:
1. Switch power on to unit.
2. Thermostat calls for heat.
3. VFD sends power to Blower.
4. Blower runs at low speed.
5. Combustion Blower initiates air flow through water heater closing the Prover Switch.
6. After 30 seconds, the Ignition Control provides power to the Spark Igniter and Gas Valve.
7. Ignition Control maintains spark for up to 4 seconds and monitors Flame Sensor to determine if
Burner is lit.
8. If the Flame Sensor does not detect proper flame, the Ignition Control shuts off the Gas Valve and
allows the Blower to purge the unit. At that time, the Ignition Control restarts with step 6. It will try and
ignite the main burners 2 more times. If the unit does not light, the Ignition Control will wait 15 minutes
and then restart at step 6. This cycle will continue until the unit lights or the power is shut off to the
unit.
9. If the Flame Sensor detects proper flame, the Ignition Control will allow the unit to operate until the
thermostat is satisfied.
10. Once the unit is satisfied, the Thermostat will shut off the Blower, Gas Valve and Ignition Control and
the unit will be in standby mode until another call for heat is initiated by the thermostat.