A defrost cycle is the scheduled or automatic process by which frost accumulation on a refrigeration unit’s evaporator coils is melted and drained, temporarily pausing active cooling and requiring careful management to prevent unacceptable product temperature rise.
In trade practice
In reefer units, defrost cycles are programmed into the controller and typically run at set intervals; the duration and frequency are visible in controller download data reviewed at delivery. QA teams examining temperature logs must be able to distinguish a normal defrost event, which produces a brief, controlled air-temperature rise, from a genuine cold-chain failure. Excessive frost build-up between cycles usually indicates high humidity ingress caused by poor door discipline or damaged door seals. Buyers may request controller settings as evidence that defrost parameters were appropriate for the cargo.
In a specification
A reefer transport specification may state the maximum permitted defrost duration and the air-temperature ceiling during a defrost event, with controller records to be provided as part of the proof-of-temperature documentation.