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Whenever the motor current demand limit set point is reached, it activates a capacity
override, again with a 2-step process. Exceeding 110% of the rated load amps for more than 30
seconds will initiate a safety shutdown.
The compressor high lift (surge prevention) set point will cause a capacity override as well.
When the surge prevention set point is reached, the controller normally will only hold the guide
vanes from opening. If so equipped, the hot gas bypass valve will open instead of holding the
vanes.
High Discharge Temperature Control
If the discharge temperature increases above 200 F (93 C), the guide vanes are
proportionally opened to increase gas flow through the compressor. If the leaving chilled water
temperature drops 5° F (2.8° C) below the control point temperature, machine will enter the
recycle mode.
Click here for Table 3 — Protective Safety Limits and Control Settings
Click here for Table 4 — Capacity Overrides