Building HVAC (Equipment w/Factory Installed Controls)
30GX Air-Cooled Screw Chillers
Guide Specifications (Controls)
Air-Cooled Liquid Chiller
Size Range: 80 to 175 Tons (281 to 615 kW) Nominal
Carrier Model Number: 30GXB
2.1.8 Air-Cooled Liquid Chiller
2.1.8.1 General System Description
Description: Microprocessor controlled, EMS communicating, air-cooled liquid chiller utilizing HFC-134a, screw compressors, and electronic expansion devices. Chiller communicates with and sends alarm’s to, the building automation network and alarm printer, utilizing a factory installed microprocessor.
2.1.8.2 System Description: Chiller Controls, Safeties, and Diagnostics
A. Controls:
1. Unit controls shall include as a minimum: Microprocessor, LOCAL/OFF/REMOTE switch, and 2-line, 24-character per line diagnostic display with keypad.
2. Shall be capable of performing the following functions:
· Automatic compressor lead/lag switching.
· Capacity control based on leaving chilled fluid temperature with return fluid temperature sensing.
· Limiting the chilled fluid temperature pull down rate at start-up to an adjustable range of 0.2°F to 2°F (0.11°C to 1.1°C) per minute to prevent excessive demand spikes at start-up.
· Seven-day time scheduling of pump(s) and chiller(s).
B. Diagnostics:
1. Display module shall be capable of displaying setpoints, time, system status (including temperatures, pressures, and percent loading), and any alarm or alert conditions.
2. Control module, in conjunction with the microprocessor, shall be capable of displaying
the output of a full load run test to verify operation of every switch, sensor, potentiometer,
fan, and compressor before chiller is started.
C. Safeties:
1. Unit shall be equipped with all necessary components, and in conjunction with the control system shall provide the unit with protection against the following:
· Loss of refrigerant charge
· Reverse rotation
· Low chilled fluid temperature
· Low oil pressure (each compressor circuit)
· Voltage imbalance
· Ground current fault
· Thermal overload
· High pressure
· Electrical overload
· Loss of phase
· Current imbalance
2 Fan motors shall have inherent over-current protection.
2.1.8.3 Operating Characteristics
A. Unit shall be capable of starting and running at outdoor ambient temperatures from 32° to 115°F (0° to 46°C).
B. Unit shall be capable of starting up with 95°F (35°C) entering fluid temperature to the cooler.
2.1.8.4 Special Features
Note:
Certain standard features are not applicable when the features designed by * are specified.
For assistance in amending the specifications, contact your Carrier Sales office.
A. Control Power Transformer:
Unit shall be supplied with a field (or factory) installed transformer that will allow supply control circuit power from the main unit power supply.
B. Proof-of-Flow Switch (Required):
Unit shall be supplied with field-installed differential pressure type proof of flow sensing switch.
C. Remote Enhanced Display:
Unit shall be supplied with indoor-mounted, remote,40-character per line, 16-line display panel for field installation.
D. Temperature Reset:
Unit shall reset leaving chilled fluid temperature based on return fluid temperature, outdoor ambient temperature, space temperature, 4 to 20 mA external signal, or Carrier Comfort Network input.
E. System Manager Multi-Unit Control:
Field-installed control shall sequence between 2 and 8 chillers and pumps.
F. Minimum Load Control:
Unit shall be equipped with factory (or field) installed, microprocessor-controlled, minimum-load control that shall permit unit operation down to 10% capacity.
G. Demand Limit Control:
Unit shall be equipped with a 2-point demand limit control (from 0 to 100%), which shall be activated by a remote contact closure or a 4 to 20 mA signal.
NOTE: The accessory control module is necessary to provide this function.