Johnson Controls SABROE Unisab III Control, Engineering Manual

Page: 143 / 348

Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
143/346
Compressor control and surveillance
In Set point 1 enter the motor top load power as stated on the name plate. In Set point 2 a lower value
can be entered for periods requiring less power. Switch between the two set points by opening or closing
a digital input, see wiring diagrams.
Open input = Set point 1 . See also 3.2 Limiting functions .
3.5.10 Thermistor connection
If the motor is fitted with thermistors to protect the motor temperature, these can be connected directly to
a digital input. See wiring diagrams.
If the motor temperature rises excessively, the compressor will stop.
3.5.11 COP set-up
UniSAB III can be set for measuring compressor COP (Coefficient of Performance), mechanical effi-
ciency and Carnot efficiency.
Together with suction/discharge pressure and temperature, the following values form the basis of the
calculations:
• Temperature of chilled liquid before evaporator.
• Volume flow of cooling gas on pressure side (m 3 /h).
• Motor power consumption in kW.
• Motor efficiency.
The COP function is enabled or disabled in the menu Configuration/Plant by setting COP active = Yes or
No .
The calculated COP values are shown in the picture Service/Diagnose/Software/COP . A more compre-
hensive description of the COP function and its setting is included in the manual UniSAB III-COP.
3.5.12 HP on two-stage
This function is used on two-stage plants to start HP compressors by force.
HP on two-stage must have been selected in the menu Setup/Configuration/Plant . The function only
works in Remote/Multisab .
A compressor is started by force by closing the input Ext start normal stop . The first compressor is now
going to start within the period of time set in the timer Start h press . After this, the compressors will regu-
late normally on the capacity regulator.
Please note that the last (stopping) compressor in operation in a Multisab system (usually the no. 1 com-
pressor in the starting sequence) will not stop on the timer
Delay before stop . It can only be stopped by
opening the input Ext start normal stop , which makes the compressor stop for a moment.