Product specifications

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B. The compressors shall be fitted with a crankcase heater, large suction filter, oil sight glass, oil strainer and
magnetic crankcase plug. The lubrication system shall be centrifugal forced feed type with external oil
equalization.
C. To maximize reliability, the compressors shall utilize across-the-line start and, to limit start-up current
draw, be limited to a maximum of 15 HP with a time delay between compressor starts.
2.10 Capacity Control
Compressor cycling shall be utilized to match the demand requirement of the system. A Proactive Full Function
Microcomputer Controller shall cycle compressors in response to leaving water temperature and
maintain water temperature within 3.0°F (1.67°C) of setpoint. This system is to provide precise and stable control
of supply water temperature over the complete range of operating conditions. It shall be capable of a system
capacity range from 100% to % at specified conditions without hot gas bypass.
2.11 Refrigerant Circuit
A. (Two compressors) (Four compressors) shall be used with a direct expansion evaporator.
B. The packaged chiller shall have no more than two compressors per refrigerant circuit.
C. The packaged chiller shall use HCFC-22 refrigerant, a positive pressure refrigerant that will not require a
purge system and is recommended by the Montreal Protocol as an environmentally safe refrigerant.
D. Insulate evaporator and other cold surfaces as required to prevent condensation at ambient conditions of
75% humidity of 90°F (32°C) wet bulb with no air movement.
E. Each refrigerant circuit shall include expansion valve, sight glass, moisture indicator, solenoid valve,
replaceable core filter-drier, liquid line shut off valves, charging and gauge connections.
2.12 Control Center
A. Control Center shall be fully enclosed in a steel, baked powder coated, control panel with hinged access
doors. Dual compartments, separating safety and operating controls from the power controls, are to be
provided. Controls shall include:
1. Compressor protection, solid state, thermal sensing overloads, with manual reset
2. High refrigerant discharge pressure, manual reset
3. Separate power terminal blocks for main power and 115vAC chiller heater power
4. Compressor starter including current sensing overload protection
5. Proactive Full Function PC Windows® Based Microcomputer Controller with factory installed
sensors including integral anti-recycle protection
6. Complete labeling of all control components
7. Numbered terminal strips and labeled components for easier wire tracing
8. Condenser pressure sensing fan cycling control for start-up and operation down to 30°F (-1.1°C).
9. (Undervoltage and phase failure protection against low voltage, phase imbalance or phase reversal).
10. (Operating and safety lights visible from unit exterior including:)
a. Control Power on
b. High pressure, high motor temperature and general alarm
11. (Control panel solenoid door latch to prevent door opening before turning off power to the unit).
12. (Electronic expansion valves which shall be controlled by the microcomputer.)
B. Control Center’s individual Full Function Microcomputer shall provide compressor staging
based on leaving water temperature. It shall have two lines of 16 large characters each Alpha-Numeric
Liquid Crystal display, and the inputs shall be through a 16 single function keypad through the menu
driven prompts. The displayed data shall be updated once per second and the microcomputer shall have
a Non-Volatile memory used for all control information. The microcomputer shall have an extended
operating range of -20°F to +158°F (-29°C to +70°C). (It shall be proactive in control and accommodate
system anomalies such as high condenser pressure and high entering water temperature by controlling
loading and refrigerant flow to keep the machine on line but at reduced capacity until the condition is
corrected.)
C. Microcomputer individual chiller controller shall provide as a minimum the following features and options.
1. Microcomputer - Unit Control shall provide the following capabilities:
a. Staging of compressors and hot gas bypass to achieve precise control of leaving liquid
b. Activating fans of the air-cooled package to control head pressure
c. 7 day time clock with schedules for machine control
d. Automatic pump down before compressor shuts down and automatic pump out before liquid
line opens on start-up.
e. Proactive control of compressor cycling and /or hot gas bypass to help prevent high pressure or
low pressure trips