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Capacity Override (Table 4)
These can prevent some safety shutdowns caused by exceeding motor amperage limit,
refrigerant low temperature safety limit, motor high temperature safety limit, and condenser high
pressure limit. In all cases there are 2 stages of compressor vane control.
1.
The vanes are held from opening further, and the status line on the LID indicates the reason
for the override.
2.
The vanes are closed until condition decreases below the first step set point, and then the
vanes are released to normal capacity control.
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.
Click here for Table 4 — Capacity Overrides