Controls
Standard Protections
Oil-Temperature Protection
Low oil temperature when the oil pump and/or compressor are running may be an indication of refrigerant diluting the oil. If the oil temperature is at or below the low oil-temperature setpoint, the compressor is shut down on a latching diagnostic and cannot be started. The diagnostic is reported at the user interface. The oil heaters are energized in an attempt to raise the oil temperature above the low oil-temperature setpoint.
High oil-temperature protection is used to avoid overheating the oil and the bearings.
Low Differential Oil-Pressure Protection
Oil pressure is indicative of oil fl ow and active oil-pump operation. A signifi cant drop in oil pressure indicates a failure of the oil pump, oil leakage, or a blockage in the oil-circuit.
During Compressor prelube the differential pressure should not fall below 12 psid. Shutdown diagnostic will occure within 2 seconds of the differential pressure falling below two-thirds of the low differential oil-pressure cutout.
Phase-Unbalance Protection
Phase-unbalance protection is based on an average of the three phase-current inputs. The ultimate phase-unbalance trip point is 30 percent. In addition, the RLA of the motor is derated by resetting the active current-limit setpoint based on the current unbalance. The RLA derate protection can be disabled in the fi eld-startup menu.
The following derates apply when the phase-unbalance limit is enabled:
10% unbalance = 100% RLA derate | 15% unbalance = 90% RLA derate |
20% unbalance = 85% RLA derate | 25% unbalance = 80% RLA derate |
30% unbalance = Shutdown | |
Phase-Loss Protection
The controller will shut down the chiller if any of the three phase currents feeding the motor drop below 10 percent RLA. The shutdown will result in a latching phase-loss diagnostic. The time to trip is 1-3 seconds.
Phase Reversal/Rotation Protection
The controller detects reverse phase rotation and provides a latching diagnostic when it is detected. The time to trip is 0.7 seconds.
Momentary Power Loss and Distribution Fault Protection
Three-phase momentary power loss (MPL) detection gives the chiller improved performance through many different power anomalies. MPLs of 2.5 cycles or longer will be detected and cause the unit to shut down. The unit will be disconnected from the line within 6 line cycles of detection. If enabled, MPL protection will be active any time the compressor is running. MPL is not active on reduced-voltage starters during startup to avoid nuisance trips. The MPL diagnostic is an automatic reset diagnostic.
An MPL has occurred when the motor no longer consumes power. An MPL may be caused by any drop or sag in the voltage that results in a change in the direction of power fl ow. Different operating conditions, motor loads, motor size, inlet guide vane (IGV) position, etc. may result in different
