Pump-Down and Pull-Down Setpoints
(For Future Software Releases)
Pump-down
•The Pump-down set-points define a method of “pumping” down a chiller, which is to draw off refrigerant from the chiller. The purpose is to prevent liquid refrigerant from developing in the chiller during an off cycle, and then being drawn into the compressor when it restarts. This feature can be enabled or disabled from this menu. If Pump-down is enabled, this feature will only function when the compressor is in Auto mode. If Pump-down is enabled, then:
•The Auto-cycle feature is “disabled” automatically. Normally, the Pump-down Stop set-point will be set lower than the Auto-cycle Stop set-point. Therefore, as the suction pressure is pulled down, the compressor is prevented from shutting down prematurely via the Auto-cycle Stop set-point by automatically disabling the Auto-cycle feature.
•The compressor will be placed into “Stop” mode after the suction pressure is equal to, or goes below the Pump-down Stop pressure.
•Enable = enables the Pump-down. Uncheck the box to disable the Pump-down setpoints.
•Pump-down Stop Pressure = this setpoint defines the suction pressure value in which the compressor will cycle off. Normally, this set-point is set below the Suction Pressure Auto-cycle Stop Pressure Set-point.