21
Fig. 15 Schematic construction of gas train, 7 and 9
sections
Fig. 16 Schematic constr. of gas train, 11 to 19 sections
Legend
A
Gas cock (hand-operated)
MP
Measuring point
F
Gas filter
VA
Safety valve
DR
Gas governor
MB
Multibloc
IT
Ignition transformer
HB
Main burner
FD
Flame control
---
Not supplied as a standard feature.
7.4.2 Specification
Multibloc with gas/air ratio control consisting of:
- Gas filter (7 and 9 sections only)
- Two safety valves
- Pressure regulator for gas/air ratio.
7.4 Standard electronic gas train
7.4.1 Schematic construction
7.5 Functions
7.5.1 General
The equipment supplied ensures that the following func-
tions are monitored and locked or blocked in case
a failure has occured.
7.5.2 Flame protection (lock out)
Flame protection with two ionization probes.
7.5.3 Low-water protection
Low-water protection is ensured with three temperature
sensors: a flow temperature sensor, a return temperature
sensor and a water temperature sensor installed in the
boiler block at the most sensitive spot (heat exchange
temperature sensor).
The sensors monitor the rate of increase in water tempe-
rature and the differential temperature across the boiler.
If for instance one of the sensors signals a water tempe-
rature increase which is too rapid, the boiler will be shut
down.
If the differential temperature across the boiler exceeds
45°C, the boiler will go into a control stop.
7.5.4 Temperature protection
Water temperature protection is ensured with three water
temperature sensors: a flow temperature sensor, a return
temperature sensor and a water temperature sensor
installed in the boiler block at the sensitive spot (heat
exchanger temperature sensor).
If the flow sensor signals a temperature which exceeds
or threatens to exceed the preset maximum operating
tempe 5°C (see para. 7.3.2), the boiler is
switched off (control stop).
At the same time the rate of increase in the water tempe-
rature is monitored, so that the boiler is switched off in
time and heat transfer is prevented.
If one of the sensors still signals a water temperature
higher than 110°C, the boiler will lock out.
The flue gas temperature is limited by a flue gas tempe-
rature sensor (locking) with a default setting of 230°C.
7.5.5 Flue gas transport protection
The flue gas transport is protected by a pressure
differential sensor.
VA2
VA1
VA2
VA1
