Stulz Tel-Air-2 Series, Operating Instructions Manual

Page: 66 / 72

E/0618/35A/66
12.9 Soft start for three-phase compressor
– SOFTT
Hazardous voltage: will cause death or serious injury. Disconnect power before
working on equipment.
Setting of this component is made in factory and must not be altered.
The soft start is installed inside the e-box on the supply line to the compressor. Its purpose is the
reduction of compressor starting current. This can be obtained in two ways:

Soft start is the most common method of starting. The initial torque setting is DIP switch
selectable as a percentage of the locked rotor torque (LRT), ranging from 15…65% of full
value. The starting time is customer set, ranging from 2…15 seconds.

Current limit start is used when a limitation of the maximum starting current is necessary. This
is DIP switch selectable and can be adjusted from 150…450% of full load amps. The current
limit starting time is customer set, ranging from 2…15 seconds.

Other operation modes of this device are kick start and soft stop, but these must be disabled
for the control of the air conditioner.
Additional features:

Motor overload: The overload is DIP switch selectable. The overload trip class is selectable for
OFF or a 10, 15, or 20 protection. A current transformer (CT) monitors each phase. The
motor’s full load current rating is set by a potentiometer. The overload reset option can be
operated either manually or automatically.

Fault indication: this device monitors both the pre-start and running modes. A single LED is
used to display both RUN/ON and FAULT indication. If the controller senses a fault, it shuts
down the motor and the LED displays the appropriate fault condition. The controller monitors
the following conditions:

Overload

Over-temperature

Phase reversal

Phase loss / Open load

Phase imbalance

Shorted SCR
Any fault condition will cause the auxiliary contacts to change state and the hold-in circuit to
release. All faults can be cleared by either pressing the reset button or by removing control
power. Overload and over-temperature are time-based conditions that may require waiting for
some additional cooling time, before reset is possible.
Control terminal description
The device contains eight control terminals on the front of the controller. These control terminals
are described below.