YORK YCAV — High Discharge Pressure

The panel lists this fault as High Discharge Pressure. For the software cutout, the manual shows the status line as SYS followed by the system number, a status field, and HIGH DISCHARGE PRESSURE. The status field shows a “FAULT” condition that will restart when the 120 second anti-recycle timer times out, or the condition in which the system will not restart until the operator clears the fault using the keypad.

This message is the discharge pressure safety for the affected system. The software High Discharge Pressure Cutout faults the system with a controlled ramped shutdown when discharge pressure rises above the programmed cutout — 274 psig at the default setpoint — for 0.5 seconds. The mechanical HPCO (Hardware) protects against dangerously high discharge pressure: it shuts the system down immediately when its contacts open, without the 3 second wait that is typical of most system faults, and because it is wired in series with the VSD Run Signal, the Chiller Control Board checks it only while the system is running. The fault table gives the shutdown style for this message as Ramped when Soft Shutdown is Disabled, and Soft Ramped when Soft Shutdown is Enabled and the Discharge Pressure Cutout is below 200 PSIG.

• Coils dirty.
• Coils damaged.
• Fans NOT operating.
• System is overcharged.

1. Check the coils and clean them if dirty.
2. Comb out fins on damaged coils.
3. Check the fan fuses.
4. Check the fan rotation.
5. Check the fan motor/blade.
6. On an overcharged system, remove charge and check subcooling.

• Discharge Pressure Cutout (Program mode): default 274.0 PSIG (18.89 Barg); for software 031-03476-225 and 031-03476-AGR the low limit is 180.0 PSIG (12.41 Barg) and the high limit is 274.0 PSIG (18.89 Barg).
• Software trip: discharge pressure above the programmed cutout for 0.5 seconds.
• Restart and start inhibit: the system restarts when discharge pressure falls to 259 psig and is inhibited from starting above 259 psig; on software build -225 or -AGR starting is inhibited above the programmed cutout - 15 PSIG.
• Hardware HPCO: opens at 297 +/-8 PSIG, closes at 230 +/-10 PSIG.
• Load limiting before the trip: loading is normal below Cutout - 20 PSIG and inhibited between Cutout - 20 PSIG and Cutout - 15 PSIG; from Cutout - 15 PSIG to the Discharge Pressure Cutout the system performs forced unloading every 2 seconds, stepping 1 Hz per 1.5 PSIG from 0 Hz to 10 Hz. The discharge pressure unload point is fixed at 255 PSIG.

After a software trip the system comes back on its own once discharge pressure falls to 259 psig and the 120 second anti-recycle timer has timed out; when the display shows the manual-reset condition, the system will not restart until the operator clears the fault using the keypad. On panels with software p/n 031-03476-101 or 031-03476-104, a high discharge pressure or HPCO fault requires a manual reset: the manual directs accessing PROGRAM mode and entering 7663 to reset the fault. On corrected software the per-system HPCO reset prompt, answered YES or NO, displays as intended; earlier software showed FLASH CARD UPDATE at that point instead.