10/2010 - Art. Nr. 4200 1030 6900A
5
Operation
Fuel-air compound control
Gas valves and instruments group
en
Fuel-air compound control
This compound control system with
precision-adjustment capability has
been designed to allow the fuel and air
flow rates to be steadily varied in sliding
mode for an adjustment of the fuel-air
ratio over the whole control range.
In the two-stage sliding control concept
the partial-load and full-load positions
are within the control range. Depending
on the heat demand these two load
points will be selected in sliding mode. A
larger fuel feed will not be suddenly
turned on or off. In the stepless control
mode the load will be controlled at any
point within the control range depending
on the heat demand. The two-stage
sliding and the stepless control concepts
are different only in the control systems
used with the burners. The same mode
of operation is used for both versions.
Mechanical compound control:
The compound control system will be
operated by the steplessly reversible
electric drive unit in dependence of the
heat requirement. The air damper and
the gas damper will be controlled by the
same system.
To ensure an optimum air-to-fuel
adjustment over the full control range, it
will be possible to vary the position of the
air damper by means of stud bolts
incorporated in the compound controller.
Gas valves and instruments group
The gas valves and instruments group
used with the furnace will be selected
according to the specific requirements to
be met by a burner system.
The following factors must be taken into
account:
• burner output
• furnace back pressure
• gas pressure loss of the burner head
• gas pressure losses of the gas valves
and instruments group
The total gas pressure loss must always
be smaller than the available gas flow
pressure.
NOTE:
Use should only be made of gas
valves and instruments that have been
approved in accordance with the burner
test specifications.
100 Burner
120 Air damper
141 Ball valve
142 Gas filter
143
Pressure gauge with stop valve
147 Test burner with stop valve
(optional)
150 Gas damper
153 Main gas solenoid valve
154 Safety solenoid valve
310 Blower
311 Minimum air pressure switch
313 Minimum gas pressure switch
314 Leak test
349 Actuator