20 Defrost Time Too Long MP4000

Description

Defrost Time Too Long 

• May occur during any defrost. 
• Heat signal has been on for too long. 
• Time limit is 90 minutes with supply voltage above 440VAC and 120 minutes below 440VAC. 
• Indicates: 
• Low power supply voltage. 
• Defective heater elements. 
• Evaporator fans running during defrost. 
• Evaporator sensor placed wrong. 

Corrective Action 

• Initiate a manual defrost and check amperage draw and evaporator coil temperature. Evaluate defrost performance. 
• Open evaporator door and check location of evaporator coil sensor. 

NOTE: This alarm can be activated at low voltage and very low box temperature conditions, even under normal operating conditions.