Check UL1
refrigeration
Description
When UL1 is de-energized or energized, suction and discharge pressures do not change as expected, and Pretrip fails in Test #5 and displays “PRETRIP FAIL AND COMPLETED”.
Activation Conditions
The pressure differential between suction and discharge pressures did not change as expected when the Front Unloader (UL1) 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 for Alarms: Check for alarm 00085 Check UL1 Circuit or P00144 Check UL1 Circuit. Alarm conditions must be corrected and the alarm cleared to continue. 3. Check System Pressures a. Install manifold gauge set to check and compare actual compressor discharge and suction pressures with those shown in Unit Data. Suction and Evaporator Outlet pressures must be above 3 psig (0.2 bar). Refer to Section 1.9.12 for instruction on comparison. b. Check transducer operation. Refer to Section 1.9.12. 4. Check Front Unloader (UL1) Operation: Refer to Section 1.8.5.5, Unloader must load and unload properly.