When selecting mounting hardware for industrial control panels, adhering to the correct din rail dimensions standard is critical for ensuring component compatibility and system safety. DIN rails provide the structural backbone for mounting circuit breakers, terminal blocks, power supplies, and programmable logic controllers (PLCs) inside equipment racks. Understanding the precise mechanical specifications of these rails and their associated clips ensures that engineers and technicians can design robust electrical assemblies that meet international IEC and EN safety protocols.
DIN Rail Dimensions Standard
The din rail dimensions standard was originally established by the Deutsches Institut für Normung (DIN) in Germany but has since evolved into European (EN) and International (IEC) standards, specifically IEC 60715. This standardization ensures that electrical components from different manufacturers can be mounted interchangeably on the same rack system.
While the “Top Hat” rail is the most ubiquitous, the standard encompasses several specific profiles, each designed for different weight loads and spatial constraints. The integrity of an electrical installation depends on selecting the correct rail profile. Using a rail with insufficient depth or thickness can lead to flexing under the weight of heavy transformers or PLCs, potentially causing disconnections or grounding failures. Conversely, over-specifying the rail size can waste valuable space within a crowded enclosure.
DIN Rails Types and Their Specifications
To navigate the din rail dimensions standard effectively, one must distinguish between the four primary rail types utilized in modern industrial automation.
Top Hat Rail (TS35)
The TS35 is the industry workhorse. It features a symmetrical hat-shaped cross-section. The standard width is 35mm, making it compatible with the vast majority of modern control gear.
- 35mm x 7.5mm (Standard): This is the most common version, typically made from 1mm thick zinc-plated steel. It is suitable for lighter components like miniature circuit breakers (MCBs), relays, and terminal blocks. The shallow depth saves space in the cabinet.
- 35mm x 15mm (Deep): Also known as “High Hat” or “Deep DIN,” this version maintains the 35mm width but increases the depth to 15mm. The material thickness is often increased to 1.5mm or 2.3mm. This profile is engineered for heavier components, such as large power supplies and heavy-duty contactors, providing superior rigidity and resistance to torsion.
Miniature Top Hat Rail (TS15)
The TS15 rail is a smaller version of the standard top hat, measuring 15mm in width and 5.5mm in depth. It is exclusively used for mounting miniature components in space-constrained environments, such as small junction boxes or compact control units.
G-Type Rail (TS32)
The G-rail features an asymmetrical “G” shape. It measures 32mm wide with a standard depth of 15mm on the high side and a shorter lip on the low side. While less common in new designs, it is still specified for mounting heavy, high-power components. The “G” shape prevents components from being installed upside down, offering a polarity protection mechanism mechanically.
DIN Rail Dimensions Standard Specifications Table
The following table provides a detailed breakdown of the physical measurements required for compliance. Engineers should consult this data to ensure the din rail dimensions standard is met for their specific application.
|
Rail Type |
Designation |
Width (mm) |
Height (mm) |
Material Thickness (mm) |
Slot Dimensions (mm) |
Standard Length |
|
Top Hat Standard |
TS35 / 35×7.5 |
35.0 ± 0.3 |
7.5 ± 0.2 |
1.0 |
6.3 x 18.0 |
1m / 2m |
|
Top Hat Deep |
TS35 / 35×15 |
35.0 ± 0.3 |
15.0 ± 0.2 |
1.5 or 2.3 |
6.3 x 18.0 |
1m / 2m |
|
Miniature |
TS15 / 15×5.5 |
15.0 ± 0.2 |
5.5 ± 0.2 |
1.0 |
4.2 x 12.0 |
1m / 2m |
|
G-Profile |
TS32 / 32×15 |
32.0 ± 0.3 |
15.0 ± 0.2 |
1.5 |
Varies |
1m / 2m |
Note: Slot dimensions refer to perforated rails. Unperforated rails are also available for applications requiring maximum structural integrity or specific grounding paths.
Material Specifications and Tolerances
The din rail dimensions standard also dictates the material composition and surface treatment of the rails to ensuring longevity and conductivity.
Steel Rails:
Most DIN rails are manufactured from cold-rolled carbon steel. To prevent corrosion, they undergo a surface treatment process.
- Zinc Plating: The most common finish, providing a bright, silver appearance. It offers good corrosion resistance in standard indoor environments.
- Chromating: Often applied over zinc plating. Yellow chromate offers superior corrosion resistance compared to clear passivation (RoHS compliant options are typically clear or blueish).
- Tolerances: The manufacturing process must maintain tight tolerances. For a 35mm rail, the tolerance is typically ±0.3mm. If a rail exceeds this tolerance, snap-on clips may not engage securely, or they may be impossible to mount.
Aluminum Rails:
Aluminum rails are used where weight is a primary concern or where non-magnetic properties are required. While they follow the same din rail dimensions standard for profile shape, they often have thicker walls to compensate for aluminum’s lower tensile strength compared to steel. They are frequently used in humid environments where steel might rust.
Copper Rails:
Pure copper rails are utilized primarily as busbars for high-current grounding applications. While they act as a physical support, their primary function is electrical conductivity. They must adhere strictly to the dimensions to ensuring that grounding clips make solid contact.
DIN Rail Clips and Mounting Accessories
While the rail provides the structure, the DIN rail clip is the interface that secures the component. Understanding clip specifications is just as important as the din rail dimensions standard itself.
Clip Mechanics and Design
A standard DIN rail clip is designed to engage with the outer flanges of the rail.
- Fixed Lip: The top part of the component usually features a fixed molded lip that hooks over the top edge of the rail.
- Spring-Loaded Latch: The bottom part of the component contains a movable clip, usually spring-loaded. When the component is pressed onto the rail, the spring compresses and then snaps the latch under the bottom edge of the rail, locking it in place.
Universal Adapters and Mounting Clips
For devices that do not have built-in DIN rail mounts (such as small hard drives, sensors, or custom PCBs), universal DIN rail adapters are used.
- Material: These clips are available in plastic (PA66 nylon) for light duties or die-cast zinc/steel for heavy duties.
- Mounting Holes: Universal clips typically feature M3, M4, or M5 threaded holes or a flat surface for adhesive mounting.
- Width: Clips come in varying widths, from 10mm narrow clips to 50mm wide brackets for larger devices.
Heavy-Duty Steel Mounting Brackets
For securing the DIN rail itself to the backplane of the enclosure, angled support brackets are used. These brackets lift the rail off the panel surface, typically by 20mm to 50mm. This elevation is crucial for:
- Cable Management: Allowing wires to pass behind the rail.
- Heat Dissipation: Improving airflow around heat-generating components.
- Access: Making it easier to access terminal screws on deep components.
Installation and Structural Integrity
Proper installation is vital to maintaining the din rail dimensions standard integrity. When cutting rails to length, it is essential to use a specialized DIN rail cutter rather than an abrasive saw. Abrasive cutting generates heat that can damage the zinc plating, leading to rust, and leaves burrs that interfere with component mounting.
Grounding Considerations:
The rail often serves as a ground bus for the mounted components. This relies on the physical contact between the rail’s metallic surface and the component’s metal clip.
- Paint Removal: If mounting the rail to a painted backplane, the paint must be scraped away at the mounting points to ensure electrical continuity.
- Perforated vs. Unperforated: Perforated rails (slotted) are convenient for mounting the rail to the panel without drilling. However, the slots slightly reduce the cross-sectional area and mechanical strength. For extremely heavy loads or high-vibration environments (like railway rolling stock), unperforated rails are preferred to maximize rigidity.
Load Bearing and Deflection
Engineers must calculate the total weight of components per meter of rail.
- 7.5mm Depth Rail: Suitable for distributed loads. If a heavy point load (like a large transformer) is placed in the center of a long span, the rail may twist.
- 15mm Depth Rail: The increased vertical web height significantly increases the moment of inertia, resisting bending.
- Standoff Spacing: To maintain the din rail dimensions standard rigidity, mounting screws usually should be placed every 200mm to 250mm along the rail length.
Frequently Asked Questions (FAQs)
What are the standard DIN rail sizes?
The most common standard sizes are 35mm x 7.5mm (standard top hat), 35mm x 15mm (deep top hat), 15mm x 5.5mm (miniature), and 32mm x 15mm (G-type). The 35mm width is the global standard for most industrial control components.
What is the difference between perforated and unperforated DIN rails?
Perforated rails feature pre-punched slots along their length, allowing for easy screw mounting to panels without drilling. Unperforated rails are solid, offering higher mechanical strength and better electrical conductivity for grounding, but they require users to drill their own mounting holes.
Can I cut DIN rail with a hacksaw?
Yes, but it is not recommended. Hacksaws leave rough burrs that can damage equipment or injure hands, and the heat can damage protective plating. A specialized DIN rail cutter tool provides a clean, burr-free cut that maintains the profile’s structural integrity.
How much weight can a DIN rail hold?
There is no single weight rating as it depends on the mounting screw spacing and rail type. A 35×7.5mm steel rail mounted every 200mm can typically support significant control gear. For heavy components like large transformers, use 35x15mm rails or reduce mounting screw spacing.
Why are some DIN rails made of aluminum?
Aluminum DIN rails are used when weight reduction is critical or for specific aesthetic requirements. However, they have lower load-bearing capacity than steel and are not suitable for use as a grounding busbar due to aluminum’s oxidation properties.
