27
5
Firing Rate Controller (optional)
5.1.6
Thermostat and Control Range
The thermostat function switches the burner on and off on the basis of the temperature and/
or pressure value, but only when burner is released by the start signal. The control range is
formed by entering the controller setpoint value and the parameters P 802 (switch-on point),
P803 (upper control range) and P 804 (burner OFF). The cut-off hysteresis is divided into 2
ranges. The first part lies above the setpoint and forms the upper control range. The second
part lies below the setpoint and forms the lower control range.
The control range may lie asymmetrically around the setpoint.
The power control unit functions within the upper and lower control range according to its set-
tings in the parameters and the default values.
If the actual value of the control unit reaches the shut-down range, the base firing rate request
is emitted. If the control unit’s setpoint exceed the shut-down range a control shut-off occurs.
This is done by internal processing. If the actual value drops below the lower control range, a
re-start can occur.
NOTICE
This function can replace the control thermostat, which is required on the plant.
It does not replace a safety thermostat.
Fig. 5-3 Control range
Summary of Contents for VMS 4
Page 2: ......
Page 119: ...118 10 Appendix...
Page 129: ...128 10 Appendix Fig 10 9 Ger t 4 Ger t 5 with output regulator...
Page 141: ...140 10 Appendix 10 14 Declaration of Conformity...
Page 142: ...141 10 Appendix...
Page 143: ...142 10 Appendix 10 15 Protocol Example...
Page 144: ...143 10 Appendix 10 16 O2 Setpoint Curves...
Page 145: ...144 10 Appendix...
