Defrost Not Complete
refrigeration
Description
Defrost did not end automatically because DTT and SAT did not reach 55°F/12.8°C within 45 minutes or SAT rose to 120°F/48.9°C; alarm only.
Activation Conditions
Defrost cycle did not terminate automatically. (DTT and SAT did not reach termination temperature of 55°F/12.8°C within 45 minutes or the SAT rose to 120°F/48.9°C during the cycle.)
Unit Behavior
Alarm Only. While this alarm is active, the defrost timer will be temporarily set to initiate a defrost cycle 1.5 hours of unit running time after the alarm comes on.
Reset Conditions
Auto Reset when defrost cycle is started again, or alarm may be manually reset via keypad or by turning the unit off, then back on again.
Corrective Actions
1. Check Evaporator Fan Clutch In Defrost: Must completely disengage fan. 2. Check Refrigerant Charge: Refer to Section 8.7.2. Charge must be correct. 3. Check for Alarm 00018 Low Refrigerant Pressure: Alarm conditions must be corrected and the alarm cleared to continue. 4. Check DTT a. Using a service (test) thermometer check temperature of evaporator tube sheet at DTT location and compare with Unit Data. Must be within 2°F (1°C) b. Check DTT and RAT wiring. Verify that RAT temperature is being displayed as RAT in unit Unit Data and that DTT is being displayed as DTT. Correct wiring if required. c. Check DTT and SAT resistance. 10K Ohms @ 77°F (25°C). Refer to Section 8.9.16 for chart of resistances for different sensors. d. Inspect DTT Should be fastened securely in place. Flat area of DTT must be against metal surface. 5. Perform Pretrip Check: Run Pretrip and check for alarms. Any active alarms must be corrected and cleared before proceeding. 6. Refer to Section 9.3.6: Refrigeration System Not Heating