33
FA ROTEX GW - 09/2012
7 x Gas burner
7 Gas burner
7.1 Structure and brief description
Controlling the burner output
The controller continuously determines the flow temperature (set
according to the operating parameters) and calculates the
necessary burner output from the nominal value and the values
of the integrated and connected sensors. The determined output
is passed to the burner fan as a PWM signal. The burner fan
immediately adjusts the gas fan speed and as such the
combustion air flow. The gas controller controls the gas volume
accordingly.
Gas/air compound control
The gas/air compound control (pneumatic compound) ensures
that, at each output, the appropriate O
2
/CO
2
content, set at the
setting screw for the gas/air mixture (fig. 7-1, item 11) and, if
necessary, at the setting screw of the gas pressure controller
(fig. 7-1, item 12) is maintained. The burner immediately
responds to every change in the air flow volume through the
gas/air compound control with a corresponding change in the gas
flow volume.
The gas/air compound control (pneumatic compound) consists of
a venturi nozzle mounted on the blower intake side (fig. 7-1,
item 21) with a ring-shaped gas inlet, the gas supply for the
burner and a gas pressure controller.
A vacuum forms in the centre of the Venturi nozzle depending on
the volume flow of the combustible air. This causes the gas to be
sucked into the centre of the Venturi nozzle, conveyed through
the burner fan to the burner surface and optimally mixed.
The gas valve can be adjusted for supply pressures up to
60 mbar (zero pressure controller).
7.2 Unlocking in the event of fault shutdown
Safety function
The gas automatic firing unit starts and monitors the firing
program process. This is followed by a fault shutdown:
– if the starting speed of the burner fan is not achieved,
– if a flame signal is present during pre-ventilation,
– if no flame is formed at the start (fuel release) after 5 sec
(safety period) (5 start attempts),
– if no flame is able to start or a flame failure during operation,
or failed program repetition.
– if no sensor values or implausible sensor values are present,
– if the safety temperature limiter (STB) is triggered.
– if inadequate water pressure available.
Unlocking the burner
The fault shutdown of the burner is displayed by the symbol
and a fault code on the display on the control panel.
A one-off burner fault can be reset by the operator.
Ɣ Reset the burner by pressing >2 sec on the button
(fig. 6-1, item 3) on the burner controller.
Ɣ If there are several shutdowns due to faults successively, a
heating technician must check the heating system (e.g. flue
system, fuel supply, water pressure) and rectify the cause of
the fault.
EXPLOSION AND POISONING HAZARD!
Escaping gas is a direct threat to human health and
safety. Even a few sparks can cause major explo-
sions.
Ɣ Only heating specialists authorised and trained by
the gas or power supply company should be
allowed to work on gas-conducting parts.
1 Burner surface
2 Blower
3 Safety gas control block
4 Gas/air combination controller
5 Gas solenoid (1 class B and 1 class C)
6 Gas automatic firing unit Siemens LMU84 (integrated in the con-
troller)
7 Measurement connection OUT - output gas pressure
8 Gas supply to burner
9 Measurement connection IN - input gas pressure
10 Measurement connection - gas pressure at the composite control-
ler
11 Gas/air mixture set screw
12 Gas pressure regulator setting screw
13 Burner flange
14 Ionisation electrode
15 Ignition electrodes
16 Ignition transformer
17 Burner flange seal (sealing cord)
18 Flame tube seal (flat seal ring)
19 Boiler flange seal (lip seal ring)
20 Burner flange channel
21 Venturi nozzle
Fig. 7-1 Gas burner on the ROTEX GW
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