Check UL2
refrigeration
Description
UL2 did not change suction and discharge pressure as expected; Pretrip fails in Test #5 and shows “PRETRIP FAIL AND COMPLETED”.
Activation Conditions
The pressure differential between suction and discharge did not change as expected when the Rear Unloader (UL2) was de-energized / loaded (discharge pressure should rise and suction pressure should drop) or when it was energized / unloaded (discharge pressure should drop and suction pressure should rise.
Unit Behavior
Pretrip will fail in Test #5 and display “PRETRIP FAIL AND COMPLETED”.
Reset Conditions
Auto reset if Pretrip is started again, 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 Wiring to CDP and CSP a. Verify that correct wires are connected to each transducer. Plugs to transducers are the same. The correct wire plug must be connected to the proper transducer. The CDP connector is identified with a red tape band while the CSP connector is identified with a blue band. b. Verify that correct transducer is being used in each position. Mechanical connections to transducers are the same. The Discharge Transducer should have a red marking dot on it. The Suction Transducer should have a blue marking dot on it. 2. Check Alarms: Check for 00086 Check UL2 Circuit or P00164 Check UL2 Circuit (Check UL2). Alarm conditions must be corrected and the alarm cleared to continue 3. Check System Pressures: Install manifold gauge set and check and compare compressor discharge and suction pressures with those shown in Unit Data. Refer to Section 8.9.10 for instruction on comparison. 4. Check Rear Unloader (UL2) Operation: Check operation of Rear Unloader (UL2) See Section 8.8.5.5. Unloader must load and unload properly.