13-21-615 v01 Page 39
Power Supply
- This device changes the incoming AC supply voltage to 24 volts DC for use by all unit control
devices. For 575 volt AC units only, a control transformer is provided to supply 120 volts AC input to the power
supply. A secondary fuse is provided on the control transformer. Refer to adjacent labeling for replacement
information.
Fuse Blocks -
Two Class CC fuse blocks provide line side protection for the power supply and control transformer,
as applicable.
Terminal Strip
- This provides connections for all 24 volt DC controlled devices not directly connected to the
Governor Controller.
Fan Starter
- The starter is used to provide control and overload protection for the cooling fan or the ventilation fan
of water
– cooled units with enclosure. The overload should be adjusted based on the motor nameplate amps and
the instructions located inside the cover of the electrical enclosure. Three fuses are provided. Refer to adjacent
labeling for replacement information.
Main Starter
- This starter is used to provide control and overload protection for the main drive motor. Wiring
diagrams for typical Wye Delta applications are illustrated on pages 43 thru 50.
Overload protection is provided for each motor on voltage and Wye Delta applications. The overloads are
adjustable and are factory set based on the motor nameplate amps and the instructions located inside the control
box door. Wye-delta starters employ three contactors which are controlled sequentially to provide low current
starting. For wye-delta starters, the motor nameplate amps must be first multiplied by 0.577 before using the
heater table.
Compressor Capacity Control, Turn Valve Units Only
– The capacity of the compressor is controlled by the
action of the turn valve and the compressor inlet valve.
The turn valve controls compressor delivery to match demands of 40% to 100% of the compressor’s maximum
capacity. The inlet valve throttles to control compressor delivery to match demands of 0% to 40% of the
compressors maximum capacity.
Example with normal setting of 100 PSIG:
Compressor Delivery
Capacity
Inlet Valve
Turn Valve
Discharge Manifold
Pressure
Full
Open
Closed
100
70%
Open
50% Open
100
40%
Open
Full Open
100
30%
Closing
Full Open
103
20%
Closing
Full Open
103
0%
Closed
Full Open
103