YORK YK — HIGH OIL PRESSURE

The shutdown message is printed as MON XX:XX AM - HIGH OIL PRESSURE. The only display variant the manual gives is the text HIGH OIL PRESSURE itself. In the control center documentation the alarm is abbreviated EHOP for the economizer compressor and PHOP for the primary compressor.

This is a safety shutdown on high differential oil pressure. The chiller has shut down because the oil pressure has increased to 90 PSID (620 kPa). The manual measures low oil pressure (LOP) at the oil sump and high oil pressure (HOP) at the compressor bearing input, and the trip is classified as a differential oil pressure shutdown. A restart is permitted only once the oil pressure has decreased to 59 PSID (407 kPa), so the unit stays shut down until that value is reached.

• The differential oil pressure rose to the shutdown point of 90 PSID (620 kPa) — this is the condition the message reports.
• A defective oil pressure transducer. The operating analysis chart lists a defective transducer when unusually high oil pressure is displayed while the oil pump is running; the remedy given is to replace the low or high oil pressure transducer.
• A misadjusted relief valve. The same analysis row lists Relief valve is misadjusted as a possible cause of the unusually high displayed oil pressure.

1. Press the oil pressure display key and read the oil pressure while the oil pump is running; this is how the operating analysis chart observes the unusually high pressure.
2. Judge the reading against the printed values: 90 PSID (620 kPa) is the shutdown point, and 59 PSID (407 kPa) is the pressure at which a restart becomes allowed.
3. If unusually high pressure is displayed with the pump running, replace the low or high oil pressure transducer, since the chart names a defective transducer as the cause. The high oil pressure transducer and its O-ring are also listed among the ten year package items in the service parts guide.
4. Check the relief valve: the chart lists a misadjusted relief valve and calls for adjusting the external relief valve.
5. When the pressure condition has been corrected, restart the chiller as described under reset below.

• Shutdown point: 90 PSID (620 kPa) differential oil pressure.
• Restart permitted when the oil pressure decreases to 59 PSID (407 kPa).

The restart stays blocked until the oil pressure decreases to 59 PSID (407 kPa). Once that value is reached, the manual's instruction is: To restart the chiller, press COMPRESSOR switch to STOP/RESET position and then to the START position.