The 2013 module on selecting refrigerated vehicles, published by Turkey's Ministry of National Education, states the rule with a number. Before loading, the refrigeration system is run until the inside of the body comes down to the product's carriage temperature. If there is not enough time for that, the body may be at most 4 °C warmer than the carriage temperature. Chilled or frozen goods are never loaded into a body that has not been pre-cooled.
The four degrees are an allowance for the body, and they cannot be used as a tolerance when accepting product. A body working in a -18 °C regime may be at -14 °C, but the product itself still has to arrive at -18 °C. Frozen goods that reach the dock at -14 °C cannot be accepted on the strength of this sentence.
Why the unit cannot do this job on the road
The module explains the reason. The materials the body is built from store heat, and pre-cooling removes that heat together with the heat of the air inside. Refrigerated vehicles used in transport are not designed to pre-cool or freeze product, and a vehicle that cannot draw the product's heat away in the time required lets food start to spoil.
The Thermo King Precedent manual, p.125, makes the same point: the unit is designed to hold product at the temperature it was loaded at, and it is not designed to pull a warm load down. The same page asks for the unit to be switched off before the doors open, to limit frost on the evaporator coil and heat gain in the trailer, and allows it to keep running when loading from a warehouse dock with door seals. The instruction covers the C-600M, S-610M and S-610DE models.
Pre-cooling does a second job as well: the module notes that it exposes a vehicle with a faulty refrigeration system before any goods go in. A body that will not reach its target empty will not reach it loaded either, and finding that out on the dock saves the load.
Three separate checks on the dock. Body, product and unit are checked separately, because one can be in order while another is not. An empty body may be at target while warm product brings in extra heat; product may be at the right temperature while a door left open or a unit in alarm puts the load at risk. The pre-cooling time is not a fixed number of minutes either: it changes with outside air, body size and unit mode.
| Check | Record | Release question |
|---|---|---|
| Empty body | Internal temperature, measurement point, time | Is the body at carriage temperature or no more than 4 °C above it? |
| Product | Product temperature, batch or pallet reference | Is the product at its own carriage temperature? |
| Unit | Mode, alarm, run record | Is the unit ready to hold the post-loading condition? |
| Door and dock | Open time, loading sequence | Does the loading plan limit unnecessary heat entry? |
| Exception | Nonconformity and responsible decision | Was loading stopped, or the decision recorded? |
Body and product readings go on separate lines, each with the time, sensor position and pallet or batch reference. If the trip record holds only readings taken on the road, a dispute cannot tell whether the load went into a warm body or warmed up in transit; the one reading taken before loading answers that question.
That reading belongs on the first line of the record for the cold chain at a distribution centre.
Pre-cooling the product is a separate job done at the plant: the module describes meat and fish being cooled after slaughter, and fruit and vegetables straight after harvest. Where insulated containers such as GEBHARDT Isotec are used instead of a refrigerated body, the container is pre-cooled too; GEBHARDT recommends 12-20 hours at 0-2 °C for fresh goods and at -21 to -25 °C for frozen goods.
After pre-cooling, check the loading sequence and the airflow as well. Door openings and the stacking pattern shape the prepared body's temperature record from that point on.
