At what PSI do the LPACs unload for lead, standby, and emergency standby units?

At what PSI do the LPACs unload for lead, standby, and emergency standby units?

• A. 125 / 120 / 115
• B. 130 / 125 / 115
• C. 120 / 110 / 105
• D. 110 / 105 / 100

Answer: (A)

LPAC unloading thresholds are the pressures at which each compressor stops delivering air to regulate system pressure. The lead (primary) unit is set to unload first at the highest threshold, so the most capable unit reduces its output while the other units can still supply air. The standby unit unloads next at a lower threshold, providing a staged reduction to maintain enough pressure while keeping a reserve online. The emergency standby unloads last at the lowest threshold, ensuring that critical systems still have air unless it becomes necessary to shed more units. This order preserves readiness and provides a controlled handoff among units as pressure changes.

LPAC unloading thresholds are the pressures at which each compressor stops delivering air to regulate system pressure. The lead (primary) unit is set to unload first at the highest threshold, so the most capable unit reduces its output while the other units can still supply air. The standby unit unloads next at a lower threshold, providing a staged reduction to maintain enough pressure while keeping a reserve online. The emergency standby unloads last at the lowest threshold, ensuring that critical systems still have air unless it becomes necessary to shed more units. This order preserves readiness and provides a controlled handoff among units as pressure changes.