YORK YCAV — SYS X LOW DIFF OIL PRESSURE

The panel line reads SYS X LOW DIFF OIL PRESSURE, where X is the system number. The manuals print the full line as SYS X YYYYYYY LOW DIFF OIL PRESSURE; the YYYYYYY field indicates a "FAULT" condition or "LOCKOUT".

This is the Low Differential Oil Pressure Cutout Fault. It trips when the differential between oil and suction pressure falls below the cutout, and it produces a controlled ramped shutdown. The safety protects the compressor from low oil flow and insufficient lubrication: it assures the compressor is pumping sufficiently to push oil through the oil cooling circuit and the internal compressor lubrication system.

• The differential between oil and suction pressure fell below the cutout — the compressor was not pumping sufficiently to push oil through the lubrication system.

• The safety is ignored for the first 60 seconds of run time.
• After the first 60 seconds of operation, the cutout is ramped linearly from 0 PSID to 30 PSID in 5 to 10 minutes, based on ambient temperature: above 50°F — 5 minutes; above 45°F — 6 minutes; above 40°F — 7 minutes; above 35°F — 8 minutes; above 30°F — 9 minutes; 30°F and below — 10 minutes.
• A 30-second safety bypass below 50 Hertz applies during rampdown, so a compressor being decelerated to 5 Hertz to add an additional compressor does not trip on a nuisance low oil differential fault.

The shutdown is a controlled ramped stop. When the display shows FAULT, the system restarts automatically once the 120-second anti-recycle timer times out. After 3 faults on the same system within 90 minutes, the system locks out and will not restart until the operator clears the fault using the keypad; the fault tables describe the lockout as cleared by cycling the system switch OFF and ON.