When it comes to designing reefer racks, the question of whether to install individual reefer outlets (sockets) or group several outlets in a single enclosure (multi-gangs) is often overlooked. Past experiences or canned designs seem to be the driving factors behind selecting one of these alternatives. This is a decision that impacts both installation costs & operations, and requires some consideration.
Unfortunately, there is no simple answer to the economic aspect of the selection. The option that yields the lower installation cost will depend on the total mix of labor and materials in the specific region where the project is being executed. In order to make an educated decision, it is important to consider the following:
- Labor: Since multi-gang installations require fewer and shorter feeder cable runs, the labor required is usually significantly lower.
- Conductors: Multi-gang installations will require shorter runs of larger gauge conductors. Specifying engineers should have an idea of the cost difference. between the required conductors and the savings from their reduced length.
- Wire management: The cost of cable trays or conduits must also be considered.
- Distribution panel boards: Single-gang installations will require larger panel boards to house many individual branch circuit breakers whereas multi-gang installations will require smaller panel boards with fewer but bigger circuit breakers.
- Reefer Outlets: Per outlet cost is usually lower in a multi-gang assembly.
Generally speaking, the total installation cost of a multi-gang installation is lower than a single-gang outlet installation. In some cases, specific local conditions could render different results.
In addition to installation costs, there are several operational factors that must be considered:
- Reefer cord management: It’s easier to prevent reefer cords from getting entangled with single-gangs, as reefer outlets are located in front of the reefer container and only a small segment of the power cord sticking out of the cord case. Avoiding tangled reefer cords also minimizes the chance that an operator could mistakenly disconnect the wrong reefer.
- Automation: Some automated terminals monitor whether a plug is inserted via a plug sensing device in the reefer outlet with the goal of only allowing cranes to move reefers that have been unplugged. This model works best with single-gang outlets because there is little chance that the operator could plug the reefer into the wrong socket.
Whether the specific project calls out for single-gang or multi-gang, it is very important that the reefer outlet selected provides safety-interlocking, overcurrent, and short-circuit protection. In addition, the product should be heavy duty, designed to withstand marine environments, and preferably be UL listed.
Even though ESL can shed some light on this issue, the recommendation is for design engineers and project owners to consider the different factors before making a final decision.
ESL manufactures safety-interlocked reefer outlets and currently has over 150,000 installed across the globe.