A reefer container is a shipping container that has traded one end wall for a refrigeration machine. The unit sits flush in the front bulkhead so the box keeps standard ISO dimensions and stacks and locks like any other container, which is the reason the design works at all.
The trade off is power. A dry container needs nothing from anyone. A reefer draws current every hour it holds a load, and the handover points between ship, terminal, chassis and warehouse are where most temperature excursions actually happen, which is why transport refrigeration service treats every handover as the first thing to check.
Inside the Machine at the End of the Box
The compressor pressurizes refrigerant and circulates it through the loop. The condenser sheds the absorbed heat into outside air. The evaporator pulls heat out of the cargo space, and fans drive the chilled air under the floor through T shaped decking so it rises through the stow and returns along the ceiling.
That return air path is the part shippers underestimate. A reefer cools by moving air, so a load stacked above the marked red line blocks the return and leaves the top of the stow warmer than the display suggests.
The control panel on the front face holds the whole thing together. It carries the set point, reads the supply and return air probes, runs the defrost cycle on a timer or on demand, and writes a temperature record that travels with the shipment.
The Temperature Range and What Limits It
Standard reefer units cover a wide band, and the setting depends entirely on what is inside.
| Set point band | Typical cargo | What the unit is doing |
| Around minus 30°C | Ice cream, some seafood, certain biologics | Near the floor of standard equipment. Super freezer units go lower |
| Around minus 18°C | General frozen food | The common commercial frozen benchmark |
| 0°C to 4°C | Dairy, fresh meat, cut flowers | Airflow consistency matters more than raw cooling power |
| 2°C to 8°C | Vaccines and biologics | Any excursion gets logged and can void the shipment |
| Up to around 30°C | Bananas, some chemicals | The unit is heating the box, not cooling it |
Published low temperature limits vary by manufacturer and by unit age, and a container that reached its rated minimum when new may not do so after a decade at sea. Confirm the rated range against the specific unit before booking anything that sits near the bottom of the band.
Food Cargo and the Airflow Problem
Fresh produce keeps respiring after harvest. It gives off heat, moisture, carbon dioxide and ethylene inside a sealed box, which is why produce containers run fresh air vents at a set exchange rate while frozen cargo runs fully closed.
Get the vent setting wrong and the symptoms look nothing like a refrigeration fault. Bananas ripen early, leafy greens wilt in a box holding a perfect 2°C, and the temperature record shows no problem at all because the temperature was never the problem.
Humidity is the other half of it. Many units allow a target relative humidity, which matters for produce that dries out and for cargo where condensation on packaging causes the damage rather than the cold itself.
Running trailer mounted units instead of ocean boxes? Call 214-791-3851 for on-site service.
Pharmaceutical Loads and the Paper Trail
Medical cargo is judged on documentation as much as on arrival condition. A vaccine shipment that stayed inside 2°C to 8°C the whole way but cannot prove it is treated as a failed shipment by most receiving protocols.
Continuous monitoring is what closes that gap. Modern units log supply and return air at fixed intervals, and many now transmit live position and temperature data so a deviation gets flagged mid voyage instead of at the destination gate.
Redundancy matters at the same level, and how reefer containers are powered on each leg decides whether that redundancy is real. Backup power arrangements, genset availability during road legs and clear plug in responsibility at every handover are the practical controls that keep a controlled load compliant, and they are worth agreeing in writing before the container leaves the origin.
Containers, Trailers and Who Fixes Which
Ocean reefer containers and road trailer units share the same refrigeration principles and almost none of the same service reality. A container in a terminal stack is handled by the terminal or the line. A trailer mounted Thermo King or Carrier Transicold unit sitting dead in a yard is a call somebody has to make right now.
Texas Reefer Solutions handles the second kind with on-site reefer repair across Dallas, TX and the wider DFW metroplex. A technician reaches the trailer inside a 45 minute target window with a service truck carrying OEM and aftermarket parts for both major brands, which is what allows most repairs to finish at the breakdown location rather than after a parts order.
The price is quoted and agreed before work begins, with nothing added once the job is done. No towing is needed, the work carries a first-time fix guarantee, and drivers routinely report loads back at set point in around two hours.
Trailer unit down on I-35, I-20, I-30 or I-45? Call 214-791-3851 and a licensed technician comes to you, any hour of the night.
Frequently Asked Questions
A reefer container is an ISO box designed to move by ship, rail and road chassis, and it needs an external power source at every leg. A reefer trailer has its own diesel powered refrigeration unit and fuel supply, so it holds temperature independently wherever it is parked.
Power comes from whatever it is riding on. Ships supply dedicated reefer sockets, terminals have plug in racks, and road legs use either a clip on generator set or a chassis mounted unit. Responsibility for plugging in at each transfer point is the single most common gap in a cold chain.
Most standard units are rated to around minus 30°C, which covers ice cream, frozen seafood and much frozen pharmaceutical cargo. Dedicated super freezer units reach considerably lower for specialist loads. Rated capability declines with unit age, so verify the specific container rather than assuming the class figure.
Many do. Units commonly allow a target relative humidity setting alongside the temperature set point, which matters for produce that dries out in transit and for cargo where condensation on packaging causes the loss. Fresh air vents also manage gas exchange for respiring produce.
For trailer mounted Thermo King and Carrier Transicold units, a mobile technician handles it at the truck’s location. Compressor faults, refrigerant leaks, electrical problems, door seals and controller errors are all routinely repaired on site with parts carried on the service truck, which avoids towing a loaded trailer.
Contact Texas Reefer Solutions
Phone: 214-791-3851, answered 24/7 for emergencies
Email: justin@texasreefersolutions.com
Hours: Monday to Friday, 7:00 am to 7:00 pm. Saturday and Sunday by appointment. After hours repair available after 7:00 pm on weekdays and on weekends.
Service area: Dallas and the surrounding DFW metroplex, including Mesquite, Balch Springs, Forney, Crandall, Pleasant Grove, Heartland, Valleycreek and Rose Hill, plus the I-35, I-20, I-30 and I-45 corridors.