Start/Stop Cycle - Bosch SSB85 Service Manual

2 .3

Start/Stop cycle

Fig. 1 Burner ignition cycle diagram
If flame is detected at the end of the pre-spark period (Ignit_0) a lockout error occurs (This lockout has a maximum of 3 auto
False flame detection
resets).
If at the end of the safety period no flame is detected the control will go to post-purge to remove the unburned gas. After this a
re-ignition attempt is started following the same cycle.
Re-ignition
The number of re-ignition attempts is limited to Max_Ignit_Trials after which a lockout occurs.
The burner can only be ON continuously for a period of 24 hours.
Intermittent operation
After this the burner is switched OFF and a restart sequence follows.
Sparking stops Spark_Before_End_Of_Safety_Period seconds before the end of the Ignit_1 period to allow for ionization
Flame establishing time
detection.
Flame out too late If after Max_Post_Purge_0 time flame is still detected a lockout follows.
Safety relay test In Safety ON/OFF state the correct working of the safety relay is proven.
Once the ignition sequence is started it will be finished*. Even if the demand is taken away during the ignition sequence the
sequence up to the burn state is ended.
Demand
If during Burn_0 state the demand is taken away, a Post_Purge_Period follows at Post_Purge_Speed speed.
Tab. 1
SSB
Product description | 5
6720866940 (2017/11) US