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Understanding the Electrical Differences Between Reefer Containers and eTRUs: Why Precise Identification Matters

Erika Thorson

Generic terms like reefer, van, or freezer are often used to describe a variety of refrigerated equipment, but each type can have different electrical requirements. To ensure we quote the correct product, it’s important to understand exactly what kind of equipment will be plugged in.

Reefer Containers: The Ocean and Intermodal Workhorses

Reefer containers are typically used for ocean or intermodal shipping and come with a built-in cord and a male pin-and-sleeve plug, usually 440/480V 3-phase, 32A (IEC 60309). These cords are often visible coiled in a tray or hook on the container’s side. The container itself is a self-contained metal unit, similar in appearance to a standard shipping container, often 20 or 40 feet long.

Electric Transport Refrigeration Units (eTRUs): The Overland Option

Electric Transport Refrigeration Units (eTRUs), on the other hand, are usually mounted on trailers or trucks. Instead of a cord, they are equipped with a male inlet mounted on the unit’s exterior. The cord with the female connector is provided at the power source (dock, pedestal, or building).

Visually, eTRUs blend into the body of the trailer or appear as nose-mounted units on the front wall. At first glance, they may look like conventional diesel-powered TRUs, but the giveaway is the small inlet plate or recessed power port replacing the familiar fuel tank.

Quick visual differences:

  • Reefer Containers: Large, box-like units with a coiled power cord and male plug. Often have corner castings for stacking/shipping.
  • eTRUs: Mounted on trailers, often with no external cord. Look for an inlet plate or recessed power port on the side or front of the unit.

Why This Matters for Electrical Quotes

It’s important to note that not all containers or eTRUs use the same standard configuration. Some may have non-standard connectors or voltages depending on origin, manufacturer, or retrofit. Since pricing and product selection can vary significantly depending on the required connector or receptacle, confirming the exact electrical configuration — including voltage, phase, amperage, and plug type — helps avoid misunderstandings and ensures a safe, cost-effective solution.

Photos of the connection point, nameplate data, or equipment specifications are very helpful in making the correct selection.

If you’re looking for further assistance or ready for a project quote, Contact our team now!

Contact ESL!

How to Prevent Exploding Reefer Plugs & Connectors

Carlos Valero
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Those who have plugged in Refrigerated Containers (a.k.a “reefers”) know firsthand that water intrusion can cause reefer plugs and connectors to explode.  This is extremely dangerous and can result in injury to the operator, damage to the plug, receptacle, and surrounding equipment.  And obviously, the refrigerated cargo is no longer being cooled.  Experienced operators will even shake the plug prior to plugging in; if they suspect water is inside they know better than to energize the plug.

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Designing a Safe Reefer Connection: Part 2

Erika Thorson

Designing a Safe Reefer Connection

Increasing safety

While little has changed in the construction of the receptacles themselves over the years, ESL is constantly challenged to find new solutions that meet unique customer safety and operational requirements. Usually terminal operators have limited or no control over the maintenance and standards associated with male plugs on reefer container cables, the quality of which varies considerably. A male plug with water and salt ingress can “flash” outwards into the operator when the interlock actuator is engaged. In order to energize a receptacle from a safe distance, ESL designed a rear-actuated receptacle that removes this safety risk by requiring the operator to engage the actuator rod from behind the assembly enclosure, out of the way in case of a flashover. Since the development of our rear-actuated receptacle, ESL has installed systems at terminals in Philadelphia, Nairobi and Vancouver. In Philadelphia, ESL added LED lights on the rear of the enclosures so operators can see they have energized the correct receptacle.

Damage control

Properly treated and maintained, a safety-interlocked reefer receptacle is designed to last many years. The reality, however, is that equipment is often damaged through misuse. In our experience, the number one cause of receptacle damage is “drive-offs”, where the reefer is moved without first being disconnected. This will destroy a nylon or plastic ROA, but not a stainless steel one. Stainless steel ROA’s can be repaired by just replacing the receptacle or swapping out a safety-interlocked outlet from another ROA. In North America, the incidence of drive-offs is such that stainless steel ROAs should be considered as an industry standard. ESL also offers microswitches in the receptacle that signals whether a container is connected, regardless of whether the reefer is energized or not. This information could be sent to the terminal operating system (TOS) and an instruction to move a reefer could be blocked if it is still connected.

If you missed part  of our series  focusing on operating reefers at terminals efficiently click here.

Introducing the New Q: ESL’s Latest Innovation

Erika Thorson

Safety, Value, Quality, and Innovation have played a key role in making ESL a worldwide industry leader in the design and manufacturing of safety-interlocked power outlets for refrigerated ISO containers. With this continuing mission in mind, ESL’s new Q module provides unparalleled safety and incorporates additional advances such as high visibility indicating light and extensive cycle testing for increased product reliability.

Watch ESL’s Q Module demo video to learn how we continuously stay ahead of product safety innovations.