01/2009 - Art. Nr. 4200 1016 3900A
23
Function
Operating function
Safety function
Compact train
Note for Switzerland
A gas safety valve (item
1
) is to be
installed in the main gas inlet pipe in
accordance with SVGW gas guidelines.
Note for Germany
The draft combustion ordinance
requires that gas-fired installations be
equipped with a thermally triggered
shut-off valve (item
1
).
Description of functions
When the system is switched on for the
first time, after a power failure or safety
shutdown, after a lack of gas or after the
system has been out of operation for 24
hours, a sealing test is performed on the
gas valves with the blower motor
running before the burner is started.
After the leak check, the pre-ventilation
period of 24 seconds begins.
During pre-purge period
- Blower pressure is monitored.
- The combustion chamber is monitored
for flame signals.
At the end of the pre-purge period
- Ignition is switched on
- main and safety valve are opened
- burner starts
Monitoring
The flame is monitored by an ionisation
sensor. The sensor is insulated and
fitted to the gas head and is routed
through the baffle plate into the flame
zone. The sensor must not have any
electrical contact with earthed parts. The
burner switches to malfunction if a short
circuit occurs between the sensor and
the burner earth.
During burner operation, an ionised
zone is produced in the gas flame
through which a rectified current flows
from the sensor to the burner tip. The
ionisation current must be at least 8 µA.
Safety functions
- If no flame is produced when the
burner is started (gas release), the
burner will be switched off at the end
of the safety period, lasting no more
than 3 seconds, and the gas valve will
close.
- If the flame goes out during operation,
the gas supply is interrupted within
one second. A restart takes place.
Once the burner starts, operation is
continued. Otherwise, a safety
shutdown is triggered.
- If there is a lack of air during pre-
ventilation or operation, a safety
shutdown is triggered.
- If there is a lack of gas, the burner
does not begin operation or switches
off. A waiting time of 2 minutes
follows. This is followed by a further
start attempt. If there is still no gas
pressure, a further waiting time of 2
minutes follows. The waiting time can
only be reset by interrupting the power
supply to the burner.
Waiting times: 3 x 2 min, then 1 hour
In the event of controller shutdown
- Controller thermostat interrupts heat
request
- Gas solenoid valves close
- Flame goes out
- Blower motor runs on (14 sec)
- Valve leak check performed
- Burner motor switches off
- Burner is ready for operation
F4
Gas failure detection
F6
Air failure detection
Y13
Main solenoid valve
Y12
Safety solenoid valve
1
Thermally-triggered safety
shut-off valve (installation-
resident)
104
Gas pressure regulator
106
Screen
108
Gas ball valve (installation-
resident)
119pBr Measuring point for gas outlet
pressure
119.1
Measuring point for gas
pressure in valve space
119.2
Air pressure measuring point
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