6570d0bfcfc507001e32d777 Din Rail Enclosure

Design considerations of industrial control system enclosures

Dec. 7, 2023
Cabinet design hasn’t changed in 40 years, but advancements have given builders more choices

This is Part I of a two-part series on industrial enclosures. Read Part II.

When designing a control system, one of the things that we cannot get away from is the need for an industrial enclosure. Often forgotten in a world where hardware evolves at lightning speed, enclosures take a back seat but fill a necessary role in our systems.

Get your subscription to Control Design's print magazine, free to qualified individuals in North America.

The general design of an enclosure really has not changed in the past 40 years or so, but let us take a stroll through the showroom, as it were, and review what is out there and why.

The physical design of an enclosure serves multiple purposes. First, it provides a physical barrier between the user of the equipment and the electrical components used to control it. Second, it provides protection of the components from contaminants in the environment that the machine or process reside. This is the primary purpose of an enclosure.

Generally, enclosures are square- or rectangular-shaped. They may or may not have a back panel to which components are mounted so that the integrity of the outer enclosure is not breached by drilling through the structure. Multiple interior panels may be mounted to make use of the sides, top and bottom in addition to the larger back surface.

The choice to use side panels must include an understanding of the restriction on which components can be mounted on the adjacent surfaces, so as to not have interference.

While the size and layout of a panel is generally designed to mount all of the components that will reside in the enclosure, additional consideration needs to be applied to consider the routing of wires within the enclosure. High-voltage wires generally should not be routed with low-voltage or communications cables to protect against electrical noise being induced by the high-voltage conductors.

Further consideration should be applied to the flow of the circuits. For example, a fuse or breaker will normally have in and out terminals that are on the opposite end of the device.

It would make sense to mount the contactor, relay or drive below the protection device, but that depends on the configuration of the input and output terminals on the controlled device. Relays and contactors generally have the input and output terminals located to the top and bottom, like the protective device, so locating them below the protective device would make sense and reduce the length of wire needed to accomplish this.

Speaking of protective devices, most manufacturers have a group of auxiliary devices that can be used to daisy-chain the wiring path to reduce wiring. To use these shortcuts, the devices must be mounted adjacent to each other as the jumper components are specifically designed based on this assumption. The same is true of some relays and contactors. The same shortcut assemblies are available to reduce the wiring for these devices, as well. While this helps with panel building and footprint, it has another challenge.

Older variable-frequency drives (VFDs), for example, would have the input terminals at the top of the drive and the output—motor—terminals on the bottom. However, newer VFDs often have all of the terminations on the bottom of the device. This means that power and control wiring will be adjacent to each other and the routing of wires from the protection device may not be as advisable as, perhaps, mounting the protection device immediately adjacent to the drive.

The environment in which the enclosure resides determines some of the fine details of the physical construction of the enclosure, as well as the materials used in the construction. For example, mild steel is a common material used to make a control box. It is rigid and resists a fair bit of abuse due to normal operation activity.

However, if that control system is in an environment where water or water vapor is present, mild steel would likely rust or corrode quickly. Stainless steel would be a better construction material in this case.

What about corrosive environments? Stainless steel would also be a good choice, but powder-coated aluminum would also provide ample protection. While less resistive to physical abuse, polycarbonate would also be a good choice for an environment where corrosion exists. A consideration during the construction phase, however, stainless steel is not easy to work with compared to mild steel, aluminum and polycarbonate.

Tools used in the construction will tend to wear out more quickly when working with stainless, so extra cost considerations are part of the decision process, as well.

While the general construction of an enclosure has remained the same over the years, some recent improvements have tweaked the performance, as it were. For example, enclosures in wet environments are built to NEMA 4 or 4X standards. The primary element here is the use of stainless steel for the cabinet.

About the Author

Rick Rice | Contributing Editor

Rick Rice is a controls engineer at Crest Foods, a dry-foods manufacturing and packaging company in Ashton, Illinois. With more than 30 years’ experience in the field of automation, Rice has designed and programmed everything from automotive assembly, robots, palletizing and depalletizing equipment, conveyors and forming machines for the plastics industry but most of his career has focused on OEM in the packaging machinery industry with a focus on R&D for custom applications. 

Sponsored Recommendations

2025 State of Technology Report: HMIs, IPCs and Enclosures

Industrial manufacturing equipment often relies on human-machine interfaces, industrial PCs and enclosures to ensure system reliability and optimal performance. These components...

Custom Encoder Created for Large Rotational Applications

Large rotational applications like MRI machines, excavators, mobile equipment, forklifts and stagecraft require precise motion feedback for optimal performance, safety and efficiency...

See How One Company Customized Motion Feedback for Material Handling Applications

Encoders can be used in material handling on sorters, conveyors, in automated storage retrieval systems, on mobile equipment, automated mobile robots and more. See how one company...

Absolute vs Incremental Encoders: Which One Does Your System Need?

The right encoder makes all the difference. Incremental encoders are perfect for tracking speed and direction in dynamic motion. Absolute encoders? They remember exact positioning...