● Remote control contacts closed.
● Boiler thermostat/pressure switch contact closed.
● Differential air pressure switch contact open.
20, 21 Start-up
● Burner control safety functions are activated.
● Gas safety valve (optional) opens.
● Gas pressure recognition, pressure switch min. closed.
● Gas start release circuit (optional) closed.
22 Fan motor starts
24 Servomotors drive to pre-purge position
● Fan contactor must be closed or driven by a frequency converter. Motor sensor
must detect the motor’s rotation speed and direction.
● When a sufficient air pressure is reached, the differential air pressure switch contact
closes. Otherwise, burner control goes to a lockout. Control remains active until
controlled shutdown.
30...34 Pre-purge
● Pre-purge begins.
● If the previous shutdown was not normal or the burner has been switched off, an
automatic gas valve proving is performed.
● If burner control receives a flame signal, burner control goes to a lockout. Control
remains active until the beginning of pre-ignition.
36 Servomotors drive to ignition position.
38 Pre-ignition begins.
40... 42 First safety time TSA1, max. 10 s, begins.
● Ignition gas valve opens.*
● Gas valve 1 opens.
● Ignition gas is released to ignition nozzle.*
● An electric arc is formed. An ignition flame* is ignited by the arc.
● Gas maximum pressure control period begins. Pressure switch max. contact must
be closed, otherwise burner control goes to a lockout.
44 Interval 1, safety time TSA1, max. 10 s, ends
● First safety time, max. 10 s, ends.
● Ignition ends.
● Flame (ignition flame*) must have been ignited by now. Otherwise, burner control
does not receive a flame signal and goes to a lockout.
● Flame signal must be available to burner control from the end of the 1st safety time
until controlled shutdown.
● Flame burns at a set ignition load.
50* Second safety time TSA2, max. 10 s, begins
● Gas valve 2 opens.*
● Gas flows through a gas butterfly valve to the nozzle.*
● Main flame is ignited by the ignition flame.*
M4263 2206EN
85 (102)