Emerson 3000 User Manual
Water-Cooled Models—Self-Contained Compressor
Liebert
®
Challenger 3000
™
40
4.3.2 High Pressure Valve - 350 psig (2413 kPa) System for 3-Ton Units (Metrex Valve)
Adjustment
The valve may be adjusted using a 1/8" diameter rod. Turn the adjusting collar nut counterclockwise
to raise head pressure; turn it clockwise to lower head pressure. Rotation directions are viewed from
top of valve spring housing.
Figure 22 Metrex Valve adjustment
Manual Flushing
The valve may be flushed by rotating the socket head screw clockwise. This screw must be in the OUT
position (counterclockwise) for normal valve operation.
4.4
Motorized Ball Valve—Digital Scroll Compressors
On digital scroll units, discharge pressure is controlled by a motorized ball valve. During unloaded
operation, the pressure changes during each digital cycle could cause excessive repositions with a
pressure-operated water regulating valve. The control algorithm for the motorized ball valve uses an
intelligent sampling rate and adjustable pressure thresholds to reduce valve repositions. The valve
assembly consists of the brass valve, linkage and actuator.
4.4.1 Control
The valve actuator operates on 24VAC power and is controlled by a 2-10VDC proportional control
signal. The valve will move from fully open to fully closed in 60 seconds. At 2VDC, the valve is closed;
at 10VDC, the valve is fully open. There is a 20-second delay to position the motorized ball valve
before starting the compressor.
Table 12
Refrigerant control settings psi (kPa)
Low Pressure
Cut Out
Low Pressure
Cut In
High Pressure
Cut Out
20 (137.9)
65 (448.2)
400 (2758)
Adjusting collar nut