Liebert Challenger 3000 with iCOM

Water-Cooled Models—Self-Contained CompressorFigure 22 Metrex Valve adjustmentAdjusting collar nutTable 12Manual FlushingThe valve may be flushed by rotating the socket head screw clockwise. This screw must be in the OUTposition (counterclockwise) for normal valve operation.4.4 Motorized Ball Valve—Digital Scroll CompressorsOn digital scroll units, discharge pressure is controlled by a motorized ball valve. During unloadedoperation, the pressure changes during each digital cycle could cause excessive repositions with apressure-operated water regulating valve. The control algorithm for the motorized ball valve uses anintelligent sampling rate and adjustable pressure thresholds to reduce valve repositions. The valveassembly consists of the brass valve, linkage and actuator.4.4.1 ControlLow PressureCut OutThe valve actuator operates on 24VAC power and is controlled by a 2-10VDC proportional controlsignal. 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 valvebefore starting the compressor.Control MethodRefrigerant control settings psi (kPa)Low PressureCut InHigh PressureCut Out20 (137.9) 65 (448.2) 400 (2758)The control utilizes an upper and lower pressure threshold with a 35psi (241kPa) deadband to reducevalve movement. If the liquid pressure is between the upper and lower threshold, the valve remainsat the current position. If the liquid pressure exceeds the upper threshold the valve opens, and if thepressure falls below the lower threshold the valve closes. There are multiple adjustment bands to easedischarge pressure back into control range.39