16/28
Building Technologies Division
CC1N7785en
20.11.2017
Startup program
A Start
When control thermostat or pressurestat closes, the burner control’s sequence switch starts running. At the
same time, the fan motor connected to terminal 6 (only prepurging) receives power and, on completion of
switch-on delay time, the fan motor or flue gas fan at terminal 7 (pre- and postpurging) also receives power.
On completion of interval (t16), the control command to open the air damper is given via terminal 9. During
the running time of the motor, the sequence switch does not operate, as terminal 8, via which the motor of
the sequence switch first receives power, is not live during that period of time. The sequence switch starts
again and begins the prepurge time (t1) only after the air damper is fully open and end switch «a» has
changed over to feed power to terminal 8.
t1 Prepurge
time
with air damper fully open (nominal amount of combustion air)
Shortly after the start of the prepurge time, air pressure switch must change over, thus interrupting the
current path between terminals 4 and 13. Otherwise, the burner control would go to lockout (start of air
pressure check). At the same time, terminal 14 must be live since this current path is used to power the
ignition transformer and the fuel valves.
t3‘
With the
LOK16…
, an ignition transformer connected to terminal 15 is therefore switched on at this point in
time (long preignition). If there is no air pressure switch, the ignition transformer receives power already with
the start command. On completion of the prepurge time, the burner control via terminal 10 drives the air
damper into the low-fire position, which is determined by the changeover point of auxiliary switch (m). During
the positioning time, the sequence switch stops again until terminal 8 receives power from «m».
t5 Interval
On completion of interval (t5), terminal 20 receives power. At the same time, control outputs 9 to 11 and
input 8 are galvanically separated from the unit’s control section, so that the latter is protected against
reverse voltages from the load control circuit. The startup sequence of the burner control ends with the
release of load controller at terminal 20. The sequence switch switches itself automatically off, depending on
the time variant used, either immediately or after some so-called
idle steps
, that is, without changing the
contact positions.
Expanding flame burners with LOK16... or LGK16...
t3 Short
preignition
time
; followed by fuel release via terminal 18.
TSA Safety
time
(part load)
On completion of the safety time latest, a flame signal must be present at the input of the flame signal
amplifier, or else the burner control will initiate lockout.
Only with LOK16...:
t3n Postignition
time
(provided the ignition transformer is connected to terminal 15).
t4 Interval
until the fuel valve is released via terminal 19.
