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Building Technologies CC1N7761en
HVAC Products 19.02.2007
Function
The following description of the unit’s function refers to the startup and supervision of a
single burner. With multiflame supervision, all burners connected to the control unit are
put into operation and supervised simultaneously in the same manner. A fault causing
lockout of one of the burners therefore results in the shutdown of all burners. Prerequi-
site for the immediate restart of the non-faulty burners is the bridging of the flame safe-
guard of the faulty burner by means of an operating switch. This switch must simulta-
neously cut all control lines to the ignition transformer and the fuel valves. For connec-
tion examples, refer to the Data Sheet on the LAE10 / LFE10.
The burner starts only if:
- The unit’s switching sequence is in the start position
- The control unit is not in the lockout position, e.g. due to a faulty UV tube
- The contacts of all the control and safety devices in the control loop between ter-
minal 8 and 9 are closed
- The air pressure switch does not indicate any air pressure – if connected in the test
circuit
Faults in the flame safeguard or in the control unit prevent startup or lead to a lockout
during startup.
If the air damper is not controlled by the control unit, terminals 20, 21 and 22 must be
interconnected.
... on startup
First, the fan motor is switched on via terminal 3 and the actuator is controlled via ter-
minal 22. When the air damper reaches its fully open position, the programming
mechanism of the unit starts to run – the prepurge time commences. The minimum air
pressure set on the air pressure switch must then be reached within 10 seconds (or
within 7 seconds in operation with postpurging) and must be maintained until controlled
shutdown occurs. Otherwise, lockout will take place. A flame signal during the prepurge
time also leads to lockout. On completion of the set prepurge time, the air damper is
given the control command to return to the minimum air position. During the air
damper’s closing time, the programming mechanism does not move.
As soon as the signal contact for the minimum throttling position is operated by the
actuator, the programming mechanism starts again and now controls the program se-
quence which can no longer be influenced from outside.
- Preignition (provided the ignition equipment was not already switched on during the
prepurge time)
- Release of the 1st fuel valve connected to terminal 5 (the fuel valve of a pilot
burner which must be closed on completion of the 2nd safety time must, however,
be connected to terminal 10)
- The set safety time elapses. If no flame is established during that period of time,
lockout will be initiated (control unit always locks itself)
- On completion of an interval of 11 seconds after the release of the 1st valve, the
2nd fuel valve will be released
- The pilot burner – if present – is switched off (connected to terminal 10)
- The load controller is switched on after a further interval of 12 seconds. Now the
burner has reached its operating position. From now on, the load controller controls
the burner’s output by either increasing or decreasing the fuel throughput and the
air volume depending on heat demand (fuel / air ratio control). This can be accom-
plished in stages, i.e. by means of thermostats or continuously (modulating) by a
modulating controller
Loss of flame during operation always leads to lockout of the burner.
Prerequisites for
burner startup
)
Startup sequence...
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