Refrigerated & Cold Chain
The single most expensive misunderstanding in refrigerated freight is this: a reefer unit maintains temperature, it does not create it. Product loaded warm arrives warm. Everything else about cold chain follows from that one fact.
Temperature Is a Specification, Not a Preference
Every temperature-controlled load needs three things stated before dispatch: the set point, the acceptable tolerance either side of it, and whether the unit runs continuous or cycle. Continuous mode keeps the fan turning constantly, holding a uniform temperature and stable humidity — which is what fresh produce and pharmaceutical loads require. Cycle mode, sometimes called start/stop, shuts the unit down once the set point is reached and restarts on demand. It saves fuel and suits deep frozen product, but it is the wrong choice for anything that suffers from temperature swing.
Note that "protect from freeze" is also a temperature-controlled service. Heated reefer moves keep paints, adhesives, liquids and certain chemicals above freezing through a northern winter, and they are booked on the same equipment as frozen food.
| Service Band | Typical Set Point | Usual Mode |
|---|---|---|
| Deep frozen | -20°F to 0°F | Cycle |
| Frozen | 0°F to 10°F | Cycle |
| Chilled / fresh | 33°F to 39°F | Continuous |
| Controlled ambient | 55°F to 77°F | Continuous |
| Protect from freeze (heated) | above 32°F | Continuous |
Operational Safeguards
Pre-Cool With the Doors Closed
The trailer is brought to set point before arrival, and the doors stay shut until the dock seal is made. Pre-cooling an open trailer at the dock pulls in warm, humid air and frosts the evaporator coil, which is how a correctly set unit still fails.
Pulp Temperature at Both Ends
Air temperature in the trailer is not product temperature. Pulping the product at loading gives a defensible record of what the trailer actually received, and it is the evidence that settles a claim if the receiver pulps low at delivery.
Reefer Download on Request
Modern units log set point and return air temperature continuously. We arrange for that download to accompany the delivery paperwork on loads where the record matters.
Airflow Does the Work
A reefer cools by circulating air, not by contact. Cold air leaves the unit along the ceiling, travels the length of the trailer, drops through and around the load, and returns along the floor channels to the intake. Anything that interrupts that circuit creates a warm pocket. That is why loads must sit on pallets rather than directly on the floor, why product should not be stacked above the load line marked inside the trailer, and why a solid wall of freight pushed tight against the front bulkhead starves the return air path.
Food loads carry a regulatory dimension as well. Under the FDA's Sanitary Transportation of Human and Animal Food rule, the shipper is responsible for specifying the temperature and sanitary conditions in writing, and the carrier is responsible for meeting them and demonstrating on request that it did. As the broker arranging the move, we make sure that specification is on the rate confirmation rather than in someone's memory.
| Loading Rule | Failure It Prevents |
|---|---|
| Product pre-cooled before loading | Warm arrival — the unit cannot pull heat out of the load |
| Load on pallets, never floor-stacked | Blocked floor channels and a warm bottom layer |
| Stay below the marked load line | Blocked ceiling discharge and a warm rear of trailer |
| Air chute in place at the bulkhead | Short-circuiting air that never reaches the doors |
| Gap left at the rear doors | Crushed cases and obstructed return airflow |
Planning a Reefer Lane
Expect Less Payload
Insulation and the refrigeration unit consume both weight and space. A reefer typically carries a few thousand pounds less than a dry van and offers slightly lower interior height, so a load plan built for a van does not always transfer.
Book Around Produce Season
Reefer capacity is pulled hard by regional harvests — Florida and South Texas early in the year, California and the Pacific Northwest through the summer. Lanes competing with a harvest need more lead time, not a better negotiator.
Declare Multi-Temp Needs Early
Frozen and chilled product on one trailer requires a multi-temp unit with bulkheads, which is materially rarer equipment. It can be sourced, but not at short notice.
Tell Us the Set Point
Send the commodity, the set point and the tolerance. We will confirm the equipment, the mode and the temperature record you will receive with the delivery paperwork.