Doors, seals and closers
Damaged seals and doors that do not self-close are the most common cause of temperature drift and icing. Inspect seals monthly and replace when compressed or torn.
Condenser and evaporator condition
Both coils must be clean for the room to hold temperature. Kitchen grease accelerates fouling, so cleaning intervals should be shorter in commercial kitchens.
Defrost cycle verification
Check that defrost initiates, completes and drains. Ice on the evaporator or floor indicates a defrost or drain heater problem.
Temperature logging
Record temperatures daily and review trends weekly. Slow upward drift is a fault developing, not a bad day.
Refrigerant leak testing
Annual leak testing protects both stock and compressor life, since running low on charge shortens compressor life considerably.