Danfoss MLM116 Application Manuallines page 14

Application Guidelines
Input controlled soft start
MCI with by pass contactor
General wiring
information
14
FRCC.PC.035.A5.02
Electrical data, connections and wiring
When the control voltage is applied to A1 -
A2, the MCI soft starter will start the motor,
according to the settings of the ramp-up time
and initial torque adjustments. When the control
voltage is switched off, the motor will switch off
instantaneously.
By means of the built-in auxiliary contact (23-24)
the by pass function is easily achieved, see wiring
diagram opposite.
No heat is generated from the MCI. As the
contactor always switches in no-load condition
it can be selected on the basis of the thermal
current (AC-1).
The wiring diagrams below are examples for
safe and reliable compressor wiring. In case an
alternative wiring logic is chosen, it is imperative
to respect the following rules:
When a safety switch trips, the compressor must
stop immediately and must not re-start until
the tripping condition is back to normal and
the safety switch is closed again. This applies to
the LP safety switch, the HP safety switch, the
discharge gas thermostat and the motor safety
thermostat.
In specific situations, such as winter start
operation, an eventual LP control for pump-
down cycles may be temporarily bypassed to
Single compressors
allow the system to build pressure. But it remains
mandatory for compressor protection to apply an
LP safety switch. The LP safety switch must never
be bypassed.
Pressure settings for the LP and HP safety switch
and pump-down listed in table from section "Low
pressure".
When ever possible (i.e. PLC control), it is
recommended to limit the possibilities of
compressor auto restart to less than 3 to 5 times
during a period of 12 hours when caused by
motor protection or LP safety switch tripping.
This control must be managed as a manual reset
device.