NGW 300 / LGW 300 / GBW 300
3 Description of function
301
3
Description of function
Depending on how it is equipped, the heater is turned on
and off by a switch, a timer or the airconditioning control
unit.
An operating indicator light is available to monitor the
opearting procedure.
After the heater is switched off ,there is an after-run.
(see 3.3 "Switching off".
NOTE.
Below is a description of of the operation cycle with the
SG 1585 control unit.
3.1
Switching on
When the heater is switched on, the operating indicator
lights up. The combustion air fan and the circulating pump
start.
The vacuum switch is shut off at the proper motor speed
(low pressure) and the signal is transferred to the control
unit and processed.
After approx. 15 seconds, the high voltage ignition spark
begins. If there is a shortlived drop in voltage when the
heater is switched on in the low voltage range, the lead
time is extended.
One second later, the solenoids open in the gas pressure
regulator (after another second, the delayed-action
solenoid in the gas hose for the NGW 300 opens, if
available) and the gas-air mixture is conveyed into the
burner by means of the combustion air fan, where it is
ignited by high voltage ignition sparks.
At the beginning of the flame monitoring, the ignition spark
generator is shut down so that flame detection is not
disrupted.
3.2
When the heater is in operation
Once the operating temperature has been reached, the
control unit takes over the regulated operation, whereby
the temperature of the heat exchanger (cooling liquid) is
maintained at a virtually constant level by alternately
switching it on and off.
If the temperature rises above the upper switching point
of the regulating thermostat, the solenoids in the gas
pressure regulator close off the gas supply and the after-
run is initiated.
The flame is extinguished, but the combustion air fan and
the circulating pump continue to run.
The circulating pump remains in operation during the
control pause; the operating indicator lights up.
If the temperature falls to the lower switching point of the
regulating thermostat, the heater will be started again and
the after-run will be ended.
3.3
Switching off
When the heater is switched off, the solenoids in the gas
pressure regulator are closed and combustion ends. The
operating indicator light goes out and the after-run begins.
The combustion air fan and the circulating pump will be
switched off after approx. 125 seconds.
Switching the heater on again during the after-run is
permissible. It will restart only after the after-run has ended.
3.4
Fault lock-out
Upon detection of one of the fault characteristics listed
below, the heater performs a fault lock-out whereby the
operating indicator light goes out. The combustion air fan
and the circulating pump will be switched off after
125 seconds.
3.4.1 Faults when the heater is switched on
–
Interruption of the temperature limiter
–
Short circuit of the vacuum switch
–
Short circuit of the fan motor
–
Short circuit of the circulating pump (when
programmed)
–
Interruption of the circulating pump (when
programmed)
–
Short circuit /interruption of the flame monitor mode
–
Short circuit of the ignition spark generator
3.4.2 Faults during the starting process
–
Intrerruption of the vacuum switch
–
Interruption of the temperature limiter
–
Solenoid valves don’t open
–
Ignition spark generator defect
–
Flame monitor electrode defect
–
Flame detected in the supply line
–
No flame detected after approx. 25 seconds
3.4.3 Faults while the heater is in operation
–
Failure to reach the low voltage threshold of < 21.5 V
for a duration of 20 seconds
–
Interruption of combustion for longer than 10 seconds
–
Short circuit /interruption of the flame montor
electrode during combustion
–
Interruption of the temperature limiter during
combustion
–
Short circuit / interruption of the solenoid during
combustion
