What Is a DIN Rail? Basics and Different Types

The average person may not even know that DIN rails exist, but they perform a crucial function. DIN rails hold together some of our most important electrical components, and if you’re designing or building electrical devices, you’ve probably heard of them.

DIN rails are the metal rails inside an electrical enclosure that are used to mount circuit breakers and other types of electrical equipment. Although DIN rails have a relatively simple design, they’re extremely important for the installation, maintenance and operation of electrical equipment.

In this edition of Polycase TechTalk, we’ll discuss the basics of DIN rails and why they’re such an important part of electrical device design. We’ll also cover the many DIN rail enclosure and DIN rail kit options that are available from Polycase. To get started, we’ll go a little more in-depth on what exactly a DIN rail is and what purpose it fulfills.

What Is a DIN Rail? The Basics

A DIN rail functions as a mechanical support structure for various types of small electrical components. Some of the equipment types that you might find mounted on a DIN rail include:

• Circuit breakers
• Terminal blocks
• Transformers
• Programmable logic controllers
• Motor controllers
• Automation controllers
• Actuators
• Power supplies
• Relays

These components require solid mechanical support to ensure that they remain in place and function correctly. However, they’re usually not designed to be mounted directly to a wall or to a panel of an electrical enclosure. Instead, device designers and builders usually mount these components using a DIN rail.

A DIN rail is typically mounted either on the interior panel of an electrical enclosure or directly onto a wall. If the rail is mounted inside an enclosure, components will be mounted directly onto the rail. If the rail is mounted to the wall or onto an equipment rack, electrical components may be mounted directly onto it, or an electrical enclosure containing other components may be mounted on it.

Why DIN Rails Are Important

DIN rails aren’t the flashiest components in an electrical device, but they play a crucial role. Here’s why DIN rails are rightly considered to be the backbone of an electrical control panel:

• DIN rails make mounting electrical equipment significantly faster and easier than mounting individual components on the body of the enclosure.
• DIN rails help conserve space in electrical panels and junction boxes by reducing the amount of mounting hardware needed.
• DIN rails provide a common standard that most circuit breakers, PLCs and terminal blocks are designed to fit. This allows device designers to use parts made by different manufacturers with the assurance that they will fit the DIN rail.
• DIN rails allow components to be easily installed and uninstalled. It’s also much easier to create slight adjustments in the position of a rail-mounted component.
• DIN rails help simplify wiring designs by providing a centralized location that wiring and connectors can pass through.

The DIN rail wasn’t always around to provide these benefits. In fact, it took a group of standards-obsessed Germans to hammer out the DIN rail framework that we know and use today.

History of the DIN Rail

You’re probably wondering by now what the letters DIN stand for. It doesn’t actually have anything to do with the mechanical function of the hardware. Instead, DIN stands for Deutsche Institut fur Normung, which translates loosely as “German Institute for Standards.”

DIN is a German organization that establishes standards for industrial and electrical equipment. They developed the standards based on the original DIN rails which originated from a German company called the Rheinisch-Westfälisches Elektrizitätswerk (RWE). (There will not be a quiz on how to pronounce this.)

In 1928, RWE saw the need for a standardized support structure that could be used to mount a variety of electrical components. Early 20th century electrical panels were often constructed using a hodgepodge of components and lacked any standardized mounting system. In response, RWE created what we now know as the G rail.

These rails were originally constructed from porcelain, with a metal bus bar running along the center. Eventually, rails constructed from metal replaced the easily-damaged porcelain, and DIN rails began to look much more like the hardware that we see in electrical enclosures today.

In the 1950s, the designs developed by RWE were further standardized by DIN. The National Electrical Manufacturers Association (NEMA), who you probably recognize from their NEMA enclosure rating system, eventually adopted a compatible standard for use in the U.S. Ever since, circuit breakers, terminal blocks and other key electrical equipment have almost always been designed to comply with DIN rail standards.

Types of DIN Rails

DIN rails come in a small handful of shapes. Here are the major differences between them:

• Top Hat Rails: This 35mm design is the most common type of DIN rail, and most modern electrical components are designed to be compatible with it. These rails feature a symmetrical flange on each side that holds components in place. Top hat DIN rails can also be known as TS35 rails.
• C Rails: These 32mm rails feature a letter “C” shape that’s essentially the opposite to the top hat rail. A C rail’s flanges point inward, providing additional support for heavy components. Although once somewhat common, C rails are no longer in widespread use.
• G Rails: These 32mm rails, also called TS-32 rails or G sections, feature an asymmetrical letter “G” shape and are often used to mount larger and heavier components due to the extra support that they offer. The asymmetrical design of G rails also helps prevent components from accidentally being installed backwards or upside down.
• Mini Top Hat Rails: At only 15mm, mini top hats (or TS-15 rails) are by far the smallest size of DIN rail. They’re relatively rare and used only for applications where a small footprint is an extremely high priority.

For most applications, a top hat 35mm rail is the preferred choice due to its versatility. Polycase’s DIN rails are designed to comply with the 35mm standard for maximum flexibility and user-friendliness in a wide variety of contexts.

Key Tips for Choosing and Installing a DIN Rail

DIN rails serve a critical purpose in electrical device design, so it’s important to ensure that you select the right DIN rail hardware. These tips will help guide your selection:

• Don’t assume that your mounting rail and electrical hardware are designed to comply with DIN standards. They almost always will be, but proprietary standards do exist, so it’s always worth checking. Every mounting rail from Polycase is designed to be DIN-compliant.
• When possible, choose a DIN rail that’s designed to fit with the type of electrical enclosure you’re using. Although the DIN standards are universal, using a purpose-made DIN rail guarantees a good fit for your enclosure. Polycase’s DIN rail enclosures are available with cut-to-size DIN rails.
• If your electrical enclosure is made from metal, it’s important to choose a DIN rail made from the same material. For this reason, Polycase recommends polycarbonate enclosures and ABS enclosures as an ideal choice for devices that will have a DIN rail mounted inside, as they’re compatible with DIN rails made from a variety of metals.
• In general, a DIN rail is not designed to be used as a busbar. However, with grounding terminal blocks attached, a DIN rail can be used as a busbar for a chassis ground.
• Make sure that your DIN rails are tested by UL for compliance with relevant industry standards. Note that your specific application may have specific requirements for DIN rail construction..
• DIN rails with pre-cut mounting slots make installation easier. Polycase’s DIN rail kits offer convenient pre-cut slots and even include screws that are designed to fit snugly into mounting slots.

For more tips on installing a DIN rail the right way, see our DIN rail installation guide.

DIN Rail Kits from Polycase

Polycase offers multiple styles of DIN rails that are designed specifically to fit our enclosures. These DR Series DIN rails are each created for a perfect fit inside a specific style of Polycase enclosure and are compatible with standard 35mm DIN rails. Each DIN rail kit includes everything you need for DIN rail mounting, including a zinc plated DIN rail, two washers and screws.

Consider these options if you’re looking for a DIN rail enclosure. Each includes options for cut-to-size DIN rail kits that are designed for a perfect fit:

• Polycase WH Series: Indoor and outdoor NEMA 4X enclosures, available in ABS and polycarbonate models and featuring a hinged design.
• Polycase WQ Series: NEMA 4X outdoor enclosures with fiberglass-reinforced polycarbonate construction that resists weather and corrosion, plus an easy-access hinged latch.
• Polycase ZH Series: Another extremely tough and reliable outdoor polycarbonate hinged enclosure with a NEMA 6P rating.
• Polycase ZQ Series: Similar to the ZH Series, the ZQ Series also features a NEMA 6P rating, but uses a non-hinged design.

For applications in which you want the entire enclosure mounted on an external DIN rail, our EK Series indoor electrical enclosures are an excellent choice. These enclosures are constructed from durable ABS plastic and feature a snap-on clip that allows them to be easily mounted to a 35mm DIN rail.

Before you choose your enclosure’s DIN rail hardware, it’s important to get answers to any specific questions that you might still have. That’s why Polycase makes it easy to talk to our enclosure experts. Just call 1-800-248-1233 or contact us online. We’ll be glad to guide you through the process of selecting the right DIN rail hardware and the perfect electronics enclosure along with it.