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7 Internal Burner Firing Rate Controller
7.16 Control Range
The control range lies around the setpoint. The content of the "Burner on" parameter is sub-
tracted from the setpoint value to form the switch-on value. The value of the "Upper control
range" parameter (P 803) is added to the setpoint value to form the upper limit of the control
range. The control range may therefore lie asymmetrically around the setpoint.The shut-off
range is upwardly limited by the "Burner off" parameter (P 804). The parameter is added to
the setpoint value. If this value is exceeded, the burner is shut off.
The range between "Upper control range" and "Burner off" forms the shut-off range. If the ac-
tual value reaches this range, the to cancel firing rate controller, press key "Manual" again runs
at base firing rate.
It also follows from this that the value in "Burner Off", is generally higher than that in "Upper
control range". Otherwise there is no shut-off range and the burner is shut off on immediately
reaching the limit.
The burner 'ON' switching point also can be located above the setpoint. In this case the pa-
rameter 802 has to be set negative (<0).
7.17 Checking of the Safety Limiter
For testing purposes the safety limiter you must change the setpoint. This also causes a
change in shut-off range as well. The safety limiter can therefore be overrun in manual mode.
Fig. 7-3 Control range
*(1) = P 804
*(2) = P 803
*(3) = P 802
*(4) = P 796 - P799
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