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Siemens Building Technologies
Electronic Air / Fuel Ratio Control System
CC1P7873.1en
HVAC Products
5 Description of functions
15.10.2002
With automatic compensation of the hysteresis, the required actuator position is always
approached from the same side, that is, from below.
This means that compensation of the hysteresis must always be made after a reduction
in
output.
If there is no further reduction in output during that period of time, compensation will
take place. The extent of compensation of the hysteresis is programmable.
The extent of compensation to be programmed should be ascertained when the burner
plant is commissioned for the first time (refer to «Commissioning notes for burners»).
Sequence of operations with compensation of hysteresis:
1. The reduction in output is made.
2. The required position of the actuator is decreased by «H».
3. The required position of the actuator is increased by «H».
H = selected value of hysteresis in [V]
Note:
If a curve is programmed that decreases the position of the actuator when the output
increases, compensation of the hysteresis does
not
work.
When used in connection with
O
2
trim control, compensation of the hysteresis can be dis-
abled.
Important is the stability of
O
2
trim control that is reached with and without compensation.
Vibrations of the actuator must be avoided since they can have an adverse effect on the
combustion process, due to the mechanical play.
Mode of operation of
automatic compensa-
tion of
hysteresis
