Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
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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.
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