52
7 O
2
Trim
Key 7 more O
2
Key 6 less O
2
The setting of parameters 898 and 899 should be chosen so that the next setpoint/actual value
comparison (control pulse) only takes place if the actual O
2
value has changed visibly
(~ 60% of end value). A mark at the centre of the setpoint display indicates that a setpoint /
actual value comparison has just been performed.
No change, or change too small Increase P term, parameter 899.
7.9.7.3 Guidelines
Enter the calculated value in parameter 898.
Factory setting: 15 seconds.
The dead time is weighted as a function of firing rate.
The dead time reduces at high fire due to the higher gas velocities. The factory setting is A
reduction of 3 seconds in dead time.
Procedure for calculating the dead time at high fire, as described above.
Set the P-term in that way, that a deviation of 1…2 vol.% O
2
between target and actual value
is corrected within 4…6 steps without overshooting.
Repeat until the setpoint is reached within ca. 4…6 steps. Check control unit setting at medi-
um and high fire.
NOTICE
You may use the P-term (parameter 899) and the dead time (parameters 898 and 900) to
achieve optimisation which inter alia depends on the installation's properties; e.g. a shorter
dead time can be set if the P-term is reduced at the same time.
Recommendation:
Set control unit speed a bit slower and P-term smaller safer!!!
– Set base value for "Deactivated control” and "Air deficiency”
If a fault occurs in the O
2
trim will be deactivated, and depending on the cause the preset cor-
rection value for "Deactivated O
2
control” or "Air deficiency” would be shown as
output. The burner does not shut down.
In the event of an "Air deficiency fault” you can enforce a burner shutdown with parameter 897.
you can select the base values for deactivated O
2
trim and air deficiency in the parameter 896.
press keys F2 and F3 to select "Set O
2
"
press key 8 to confirm the query
press key 16 until the display shows "setpoint"
press key 5 up, to activate O
2
trim unit during adjustment. the display shows "T"
use the keys 6 and 7 to change the O
2
setpoint from the preset value with the range
+3 to -1 vol.% O
2
. Observe the change in the actual O
2
value simultaneously on the
display.
Control pulses too short → increase P-term, parameter 899
Overshooting → reduce P-term
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