Remote means that the compressor works together with one or more compressors in a com-
mon Multisab control system. It is possible to switch to Manual with the Manual Mode switch
in the Favourites/Default picture.
3.1.2 Regulator set-up
Unisab III includes a number of compressor capacity regulators. In the modes Auto and Re-
mote, one (and only one) of these regulators is responsible for adjusting capacity according to
the cooling (or heating) requirements. Which regulator to use is specified in line 3: Control on
in the picture Setup/Compr. Control.
Control on can be set to one of the following:
• Suction pressure
• Process out
• Discharge pressure
• Hot water
• Ext. cool
• Ext. heat
Each regulator has its own set of parameters. This means that when changing the Control on
setting from one regulator to another and back again, the original parameters are kept. Each
regulator parameter set includes:
• Set point (SP)
• Neutral zone (Nz)
• Proportional band (Pb or P Band)
Depending on whether PID = Yes or No is selected in the picture Setup/Configuration/PID,
PID parameters will also be used for screw compressors and reciprocating compressors with
VSD. See subsection 3.1.4. Capacity PID regulation (outer loop) below.
Set point is the desired pressure or temperature in the plant.
Neutral zone indicates how much the pressure or temperature is allowed to fluctuate in rela-
tion to the Sp without the compressor changing its capacity. The set value of Nz is positioned
symmetrically around the set point (Sp +/- 1/2 Nz).
Proportional band indicates how powerful the regulating signal to the compressor capacity
regulation is going to be, depending on the difference between the desired value (Sp) and the
actual value.
If the measured value is just outside the Nz, the regulating impulses will be very short where-
as the regulating impulse will be very long if the measured value is outside the P Band. The P
Band is positioned symmetrically around Sp outside the Nz. See Fig. 13.
Compressor control and surveillance
64/319
Engineering manual - Unisab III 1.10
001930 en 2014.09
To Next Page
Loading...
Need help?
General
