Product Manual AGR-3 AGR 070A through 100A
51
F.
Control System: A centrally located weatherproof control panel shall contain the
field power connection points, control interlock terminals, and control system. Power
and starting components shall include factory fusing of fan motors and control circuit;
control transformers, individual contactors for each fan motor, solid-state start timer,
solid-state three-phase motor overload protection, inherent fan motor overload
protection and unit power terminal blocks for connection to remote disconnect switch.
Terminals shall also be provided for power supply to the evaporator heater circuit.
Hinged access doors shall be lockable. Barrier panels are required to protect against
accidental contact with line voltage when accessing the control system. The
operating and equipment protection controls shall be:
Global UNT microprocessor based control that accomplishes unit capacity control by
6-stage cross-circuit compressor cycling based on leaving chilled water temperature.
Set point and control band shall easily field adjusted and anti-cycling and stage delay
relays are to be included. Equipment protection controls shall include low and high
refrigerant pressure cutouts, low evaporator flow, sensor failures, and evaporator
freeze protection. Motor protection shall include phase voltage, volts ratio, and solid
state compressor motor protection. The controller shall be equipped with a Zone
Terminal option that provides an onboard LCD display of unit operating parameters
and adjustment of any optional controls.
- OR -
MicroTech microprocessor control with a 12 key keypad and 4-line, 40 character backlit liquid
crystal display operator interface. The controller shall continuously perform self-diagnostic
checks on all system temperatures, pressures, and equipment protection controls, and
automatically shut down a circuit or the entire unit at fault conditions. The cause, time, and
date of the occurrence shall be recorded and displayed along with availability to view the
seven previous incidents.
The controller shall take proactive measures to stay on-line for non-critical abnormalities;
staging down capacity, activating a pre-alarm signal and automatically switching to the alarm
menu on the display. These pre-alarms shall be self-clearing when the off-condition is
corrected.
Critical shutdown alarms such as high condenser pressure, freeze protection, and low
evaporator pressure shall be manual reset and cleared at the keypad to resume operation.
The refrigerant discharge pressure shall be controlled by a FanTrol system that cycles
condenser fans based on discharge pressure and shall be operational 40
°
F (4.4
°
C).
- OR -
The refrigerant discharge pressure shall be controlled by a SpeedTrol control employing both
fan cycling and fan speed control and allow operation to
0
°
F (-18
°
C).
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