The last delivery does not necessarily leave an empty body: returned goods, collections or other temperature-sensitive cargo may remain. Check that first. If the body is truly empty, use the next loading time, required body condition and unit instructions to plan operation.
Define the duty-cycle boundary
Start comparisons from equivalent conditions after the final delivery and finish when preparation for the next load is complete. Measure empty travel, parking and re-cooling separately, then add them. Distinguish vehicle consumption from independently measured unit consumption, as in the refrigerated vehicle cost guide.
Unit mode and safety
Pages 23-24 of the Thermo King Precedent manual describe Cycle-Sentry and Continuous modes with setpoint, engine warm-up and battery conditions (manual). This unit-specific explanation does not transfer to every refrigeration unit. Do not impose a mode change as an automatic energy saving; authorised staff follow the manufacturer's operating instructions and the company's safety procedure for starting or stopping.
Decision table for an empty return
| Condition | Record to check | Decision |
|---|---|---|
| Returns or temperature-sensitive cargo remain | Remaining load and product requirements | Do not apply an empty-return scenario; maintain the cargo's required conditions |
| Next load requires a pre-cooled body | Load condition, target condition and start time | Plan controlled pre-cooling under the approved procedure |
| Next-load condition is unknown | Order, route and loading window | Obtain a responsible decision rather than assume |
| Body is parked and mode will change | Model instruction, battery/engine and safety record | Apply the appropriate start/stop step |
| Passive container or plates will be used | Container model, plate preparation and return record | Account for vehicle and preparation energy separately |
A hypothetical calculation illustrates the method: setup A uses 4 L on return/parking and 3 L for later pre-cooling; setup B uses 2 L and 4 L. Totals are 7 L and 6 L. The difference is meaningful only with comparable routes, ambient conditions, measurement methods, readiness times and final body conditions. It is not an actual test result or promised saving.
The Precedent manual separately checks cargo starting temperature and airflow (pp. 125-126). A comparison ending with a warmer body or unprepared cargo on one side has not demonstrated completion of the same task.
Passive containers shift preparation work to the depot. GEBHARDT's plate instructions require full solidification of the specified plates. Account separately for freezer energy, ready plate stock and container return/cleaning; not running the vehicle unit does not eliminate preparation costs.
The decision record should state the next-load condition, chosen unit mode, manufacturer's instruction and company procedure, empty-return and later pre-cooling times, fuel or electricity meters and the responsible person. Follow the safety distinction in the switching off during loading guide; without records, do not label the empty leg a total loss or make automatic shutdown a universal rule.
