Sterlco GP Series 20-60 HP Packaged Chillers - Manual (Page 17)

GP Series Portable Chillers Chapter 2: Functional Description 17 of 93
Flow Switch
The thermal dispersion flow switch cutout device, mounted in the process piping, shuts down
the chiller if it senses that the water/glycol flow rate through the evaporator has dropped
below an acceptable level. The flow switch opens the control circuit and shuts down the
pump and the chiller.
Remote Start/Stop Interlock
An additional contact is provided to allow the remote starting or stopping of the chiller. To
use this feature install a switch or dry contact interlock connected in series between terminals
4 and 23. Refer to the electrical schematic supplied in the control enclosure. Once the wiring
is complete the controller will need to be reconfigured in the supervisor settings.
2-5 Optional Features
Options marked with “*” indicate options that can be factory installed or retrofitted in the
field.
Automatic Water Make-Up*. Not available on chillers less reservoir tank. This option
includes an electric water solenoid valve, and the necessary internal piping to connect the
chiller to a make-up water source. The controller uses the standard tank level pressure
transducer to determine when to fill the tank. See Appendix for typical piping diagrams.
Customer piping must provide backflow protection and venting of tank to
atmosphere to prevent over-pressurization of the reservoir tank (not needed for
open tank). See Section 7-7 for flow schematics.
Process Water Side-stream Filter*. Not available on chillers less pump and reservoir tank.
This option includes a 50 micron filter, flow indicator, ball valve for throttling water flow,
and the necessary piping to provide constant filtering of the process water at about one gallon
per minute (1 gpm/3.8lpm).
General Fault Indicator Audible/Visual Alarm*. This option includes a 100 dB audible
alarm horn/ visual alarm strobe and silence button with provisions for customer wiring
indication interlock. The alarm signals anytime that a fault is recognized during the operation
of the chiller.
Communications Options*. This option provides the capability for the unit’s controller to
communicate with an external device using a variety of serial communication protocols.
Currently the unit can communicate over RS-485 Modbus RTU, BACNet, LONWorks,
Ethernet Modbus.
High Pressure Fans. Provides either 0.3” WC (75 Pa) or 1.0”WC (250 Pa) of external static
pressure on fan discharge. High-pressure fans are necessary and must be included in chiller
installations where exiting air exhausts through ductwork.
The 0.3” WC (75 Pa) static fan can be retrofitted without sheet metal modification, but will
require changing out fan housing, fan blades, fan motors and electrical components.
Variable Speed Fan – GPAC20-50. Reduces the speed of the fan based on refrigerant
pressure and system load, allowing the chiller to operate in ambient temperatures below 75ºF
(24ºC). This option will also reduce fan noise in lower ambient temperatures and low loads.