Check Refrigeration System
refrigeration
Description
Check refrigeration system means pulldown delta-t stays between -3.0b0F (-1.7b0C) and +5b0F (+2.8b0C) after five minutes or discharge pressure stays too low, and the unit follows the configured response.
Activation Conditions
Condition 1: When system has been operating in Pulldown for more than five minutes and delta-t (SAT - RAT) is between -3.0°F (-1.7°C) and +5°F (+2.8°C). Condition 2: Discharge pressure is not at least 5 psig (0.34 bar) higher than suction pressure for more than 10 minutes.
Unit Behavior
Condition 1: If the DTT and/or SAT temperatures are cool enough to allow a defrost the unit will go into defrost. Following defrost, if activation criteria for Condition 1 reoccur within 45 minutes of the defrost cycle, alarm or alarm and shutdown as Configured. If, following the defrost and the 45 minute wait time, the activation criteria for Condition 1 reoccur the unit will go into defrost again. If the DTT and SAT temperatures are too warm to allow a defrost, alarm or alarm and shutdown as Configured. Condition 2: Alarm or alarm and shutdown as Configured.
Reset Conditions
Auto reset when discharge pressure is more than 20 psig (1.26 bar) above the suction pressure for five minutes, or alarm has been active and unit has been shutdown more then 14 minutes or alarm may be manually reset using the display mounted keys or by turning the unit off, then back on again.
Corrective Actions
1. Check Compressor Drive Coupling: Verify that compressor couping is intact and the compressor crankshaft is turning. Repair as required. 2. Check Sensors and/or Transducers: Using an accurate temperature measurement device or pressure measurement device, check SAT, RAT, CDP, EVOP and CSP readings. Readings must be the same on measurement device and Unit Data. Refer to Section 1.9.12 for instruction on pressure reading comparison. 3. Perform Pretrip Check: Clear Active Alarm list, then run Pretrip and check for any new alarms. Any active alarms must be corrected and cleared before proceeding. 4. Check Compressor a. Perform Pump-Down Test. Refer to Section 1.8.1. Must hold a vacuum and not equalize in a short period of time. b. Cover condenser and build-up discharge pressure. Must be able to raise pressure to 400 psig (27.2 bar). c. Disassemble and inspect compressor valve plates, cylinder suction valves, cylinder discharge valves and pistons, etc. Must be intact, clean, and in good working order. Refer to Section 1.8.