SABROE UNISAB S-Control, Instruction Manual

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31
0171-761-EN
Limiting functions
UNISAB S-Control has three basic limiting
functions:
1. Low suction pressure.
2. High discharge pressure.
3. High motor current (only if a converter is
fitted, as described in the chapter entitled
Measuring the motor current ).
Note:
The above mentioned limiting functions,
which are active both for
automatic and
manual operation, overrule suction press-
ure and brine temperature regulation. This
means that the capacity of the compressor
cannot be changed if the consequence of
this change is an excess of the limiting
functions.
1. Low suction pressure
If the suction pressure falls below the war-
ning limit (please refer to the section
War-
ning limits
) the LED in the suction pressure
¯
column will begin to flash slowly, and the
compressor capacity will be reduced until
the suction pressure is higher than the war-
ning limit.
During manual operation, UNISAB S-Con-
trol will endeavour to increase capacity to
the set capacity when the suction pressure
permits this.
2. High discharge pressure
If the condensing pressure rises above the
warning limit (please refer to the section
Warning limits ), the LED in the discharge
pressure ­ column will begin to flash and
the compressor capacity will be reduced un-
til the discharge pressure falls below the
warning limit.
When the discharge pressure is more than
1.5 bar under the alarm limit, the capacity
can be increased again.
NB
During manual operation, UNISAB S-Con-
trol will endeavour to increase capacity to
the set capacity when the discharge pressure
permits this.
3. High motor current
If the UNISAB S-Control is equipped with a
signal for
measuring the motor current
(please refer to the chapter Measuring the
motor current ), the current limit function
will also be active.
The limit required (typically the nominal
current of the motor - please see the label on
the motor) should be set for motor current
­
. If this limit is exceeded, the LED will be-
gin to flash and the compressor capacity
will be reduced.
Important:
This function does not replace a thermal
overload relay, which is still required.
NB
During manual operation UNISAB S-Con-
trol will increase the capacity to the set ca-
pacity, when the motor current permits this.
When the motor current falls below 95% of
the limit value, the capacity can be increa-
sed again
.