Refrigerated Trailers (Reefer)

A refrigerated trailer — called a reefer in trucking — is an insulated enclosed trailer fitted with a diesel-powered refrigeration unit that maintains a controlled interior temperature during transit. Reefers handle freight that requires temperature management: fresh and frozen food, temperature-sensitive pharmaceutical, floral, and certain chemicals. When temperature integrity matters, a reefer is not optional.

Interior dimensions

Length: 53 feet (interior), same as dry van — though the insulated walls reduce interior usable width slightly
Width: 96 to 98 inches usable interior (insulation reduces interior width by 1 to 2 inches compared to dry van)
Height: 105 to 110 inches interior — reefer trailers vary more than dry vans due to the refrigeration unit housing on the nose of the trailer

Confirm interior height with the carrier for double-stack loads, since reefer interior height is typically 2 to 5 inches less than equivalent dry van.

Temperature range

Modern reefer units operate across a wide temperature range. The practical operating range for most trailer refrigeration units (Thermo King, Carrier Transicold) is approximately -20°F to +70°F. Most cold chain freight operates within the following common setpoints:

Frozen: 0°F or below — ice cream, frozen meals, seafood
Meat/poultry: 28°F to 32°F — fresh protein, poultry in chilled transit
Produce: 34°F to 38°F — fresh fruits and vegetables
Dairy: 34°F to 38°F — milk, cheese, yogurt
Pharmaceutical: 35°F to 46°F (2°C to 8°C) — refrigerated drugs, biologics, vaccines
Controlled room temperature: 59°F to 77°F (15°C to 25°C) — some pharmaceutical, chocolate, certain chemicals

Specify the required temperature setpoint at booking, not just the commodity type. Carriers program the reefer unit to the setpoint before loading.

Pallet positions and weight

Reefer capacity is similar to dry van: approximately 26 standard pallets at floor level, 40 to 52 positions when double-stacking is appropriate. Legal payload capacity is slightly lower than dry van — typically 42,000 to 44,000 pounds — due to the refrigeration unit's weight (600 to 800 pounds) adding to the trailer tare.

Continuous vs. cycle-sentry mode

Reefer units operate in two modes:

Continuous mode: The refrigeration unit runs constantly to maintain setpoint temperature. Required for frozen freight and sensitive cold chain loads.
Cycle-sentry (or start/stop): The unit cycles on and off to maintain a temperature range. More fuel-efficient; appropriate for fresh produce and commodities where a temperature range (not a specific setpoint) is acceptable.

Specify operating mode at booking for sensitive freight. The shipper or consignee should not find the reefer in cycle-sentry mode when continuous was required.

Fuel and pre-trip inspection

The refrigeration unit runs on diesel fuel from its own tank, separate from the tractor's fuel. The reefer fuel tank typically holds 50 to 70 gallons. On longer lanes, refueling may be required. Carriers are responsible for maintaining reefer fuel; for multi-day transit on frozen freight, this is a monitoring consideration.

A pre-trip inspection — verifying that the reefer is at or near setpoint before loading begins — is standard practice for temperature-sensitive freight. Shippers who load into a trailer that hasn't been pre-cooled take on the risk of the temperature spike during loading affecting the product. Pre-cooling typically requires 30 to 60 minutes with doors closed before freight loading begins.

What goes wrong on reefer shipments

Loading into an uncooled trailer: A reefer that was just backed to a dock hasn't pre-cooled. Loading warm product into a warm trailer, then expecting the unit to pull the temperature down while in transit, is a common error that leads to temperature excursions.
Wrong temperature setpoint: Carrier programmed 34°F, shipper required 28°F. Pharmaceutical at 38°F when 2°C to 8°C requires maximum 46°F means the load is still within spec — but frozen produce at 28°F when fresh-set at 34°F is a loss.
Door opening during transit: Every time a reefer door opens, the temperature spikes. Multi-stop reefer loads with multiple door openings in summer heat require more aggressive setpoints and higher-capacity units.
Fuel runout: If the reefer runs out of diesel on a long transit, the temperature drifts. For frozen freight in summer, a fuel runout can result in partial or total loss.

When to choose reefer vs. dry van

The choice is determined by the freight's temperature requirements. Freight with a specified temperature range during transit — regardless of whether it is frozen, refrigerated, or controlled room temperature — requires a reefer. Freight that is temperature-ambient and not heat-sensitive ships in a dry van.

Some shippers use reefer for summer protection on non-temperature-sensitive freight — chocolate, wax-based products, candles — that can melt in trailers parked in summer heat. This is a legitimate use of reefer capacity, though at a higher cost and lower availability than dry van.

For dry van freight, see dry van equipment. For open-deck freight, see flatbedeasy.com.