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10/2010 - Art. Nr. 4200 1030 6900A

Gas start-up mode

As soon as the furnace system is
required to supply heat, the burner
control circuit will close and the program
flow started. When the program has
come to its end, the burner will be turned
on.

An automatic test is made for the
tightness of the gas valves prior to
each burner start.

The air damper is in its closed
position when the burner is out of
operation.

The electric actuator will open the closed
air damper to its full-load position so that
the burner will ventilate the furnace and
the exhaust hoods with the specified air
rate. Shortly after the pre-ventilation
process has been started the lack-of-air
cut-out must change over to operating
position within a certain time, i.e. the
minimum air pressure setting must be
reached and maintained until the burner
is turned off. At the end of the specified
pre-ventilation time the air damper will
be moved into its partial-load position in
a linked control concept with the gas
damper.

The ignition transformer is activated.

After the pre-ignition time, the main gas
valves are open and the gas comes out
from injectors where it is mixed in the
combustion head with air coming from
the fan. The ignition of the gas air
mixture is done directly by a high voltage
spark on a gas injector. During the
safety time, a stable flame is formed and
is monitored by an ionisation sensor.
The ignition is stopped before the end of
the safety time and the burner operates
at its minimum power. The start-up
programme is completed.

Gas operating mode

After the flame has developed the load
regulator will be enabled which brings
the burner into its operating position.
The load regulator will now control the
burner automatically between its partial-
load and full-load stages. Depending on
the heat demand, the electric actuator of
the compound control system will be fed
with the OPEN or CLOSE command via
the regulator and thus increase or
decrease the gas and air flow rates. This
compound control system will vary the
positions of the gas control valve and air
damper and thus regulate the gas flow
rate in a linked concept with the air flow
rate. The burner can either be controlled
by a 2-stage sliding or, if a respective
controller is provided, a stepless control
concept. The stepless control will allow

the burner to be operated at any desired
stage between its partial-load and full-
load positions. The burner will always be
turned off out of its partial-load position.
The air damper will be closed when the
burner is out of operation and will thus
prevent cold air flowing through the
burner chamber, heat exchanger and
chimney. The interior cooling losses will
thus be greatly minimized.

Attention:

If there are shut-off dampers in the flue
gas tract they must be complete open.
Otherwise there will be a high danger of
low-speed detonation or explosion! The
open-position of the shut-off damper can
be assured by the integration of the
opening contact of the shut-off damper
in the safety chain of the heat generator.

General safety functions

In case a flame does not develop when
starting the burner (fuel release), the
burner controller will shut off at the end
of the safety period (shut-off on trouble).
A shut-off on trouble will also occur in
the case of flame failure during
operation, air flow failure during the pre-
ventilation phase and pressure failure
during the whole period of burner
operation. Any failure of the flame signal
at the end of the safety period and a
flame signal during the pre-ventilation
phase (external light control) will result in
a shut-off on trouble with the automatic
furnace controller being locked.

The trouble is indicated by the trouble
signal lamp lighting up. The automatic
furnace controller can be unlocked
immediately after a shut-off on trouble
by pressing the unlocking key. The
program unit will return to its starting
position and proceed with the restart of
the burner.

A voltage failure will result in a regular
shut-off of the burner. After voltage
recovery, the burner can be
automatically restarted unless another
interlock is active, e.g. one caused by
the safety circuit. In any case, the fuel oil
supply will be immediately stopped upon
occurrence of a trouble.

The control unit will stop at the same
time causing also the trouble location
indicator to stop. The symbols will
indicate the kind of trouble.

Operation

Gas start-up mode
Gas operating mode
General safety functions

Full load

Operating position

Load regulator

Release

Partial load

Ignition/Gas valves

Gas control:
2-stage sliding Stepless

ON OFF

Full load