Cable cleats are one of those components that rarely get much attention until something goes wrong. They sit quietly on cable trays and ladder racks, holding cables in place, and most people walk past them without a second thought. But in certain situations, particularly where large power cables are involved, cable cleats are the component standing between a controlled installation and a serious electrical fault.
This guide covers everything you need to know: what a cable cleat actually is, why it matters, the different types available, how to choose the right size, and how installation works in practice. Whether you are specifying a new installation, reviewing an existing one, or simply trying to understand the components involved in a cable management system, this guide covers it all.
What Is a Cable Cleat?
A cable cleat is a device that mechanically secures and supports a cable or group of cables at regular intervals along a cable route. It clamps around the outside of the cable, and is then fixed to a surface such as a cable tray, ladder rack, wall, or structural support.
The primary function of a cable cleat is to hold the cable in its correct position under all operating conditions, including during a short circuit fault. This last point is the one that most people miss, and it is the reason cable cleats exist as a product category distinct from cable ties or simple cable clips.
When a short circuit occurs in a power cable, extremely large currents flow for a brief period before the protection operates and isolates the fault. Those currents generate powerful electromagnetic forces between adjacent cables. The forces are proportional to the square of the fault current, which means even a moderate fault current can produce forces large enough to throw cables off their supports, damage insulation, and create secondary faults. Cable cleats are designed and tested to hold the cables securely against these forces so the cables stay in place and the fault is contained.
This is why cable cleats are not optional on single-core power cable installations and on any installation where fault current levels are significant. They are a safety component, not just a tidiness accessory.
Cable Cleats vs Cable Ties vs Cable Clips: What Is the Difference?
These three terms get used interchangeably in conversation but they refer to quite different products with different applications.
Cable Clips
Cable clips are the simplest form of cable support. They hold a single cable against a wall or surface using a nail, screw, or adhesive. They are used in domestic and light commercial wiring for fixed wiring runs and are not rated for any significant mechanical load. They provide no meaningful protection against electromagnetic forces.
Cable Ties
Cable ties bundle cables together or secure them loosely to a support structure. The guide on what cable ties are and how they are used explains their applications well. They are extremely useful for organising cable runs and providing light support, but they are not designed or tested to withstand short circuit electromagnetic forces. Using cable ties as the sole support method on a single-core power cable installation is not compliant with IEC 61914.
Cable Cleats
Cable cleats are engineered fasteners designed and tested to retain cables under the mechanical forces generated during a short circuit. They are manufactured to IEC 61914, which is the international standard for cable cleats. This standard defines the tests a cable cleat must pass, including the withstand load test that verifies the cleat can hold the cable against calculated fault forces. Cable cleats are specified by engineers based on the fault current level of the installation, and the correct cleat type and spacing is a calculated engineering decision, not an estimate.
Where Are Cable Cleats Used?
Cable cleats are used wherever cables need secure mechanical retention rather than just light support. The most common applications are:
Single-Core Power Cables in Trefoil or Flat Formation
This is the most important application for cable cleats. When three single-core cables carry a three-phase supply, the interaction between their magnetic fields during a fault creates the electromagnetic forces described earlier. Trefoil cable cleats hold all three cables in the correct formation, ensuring the forces are balanced and the cables cannot move.
Vertical Cable Runs
When cables are installed vertically, they carry their own weight as a sustained load on the fixings. Cable cleats provide the clamping force needed to support this load over long vertical runs, where simple clips or ties would slip or fail progressively under the sustained tension.
Industrial and Offshore Installations
In oil and gas facilities, power stations, industrial plants, and marine installations, cable routes are often exposed to vibration, thermal cycling, and mechanical disturbance. H07RN-F rubber cables and other heavy-duty cables in these environments need secure retention that will not loosen or degrade over time. Aluminium cable cleats are typically specified in these environments for their corrosion resistance and mechanical strength.
Above-Ground Outdoor Runs
Cables installed outdoors on cable ladders or external structures are subject to wind loading, UV degradation of any plastic components, and temperature cycling. Cable cleats for outdoor use need UV-resistant materials and, in coastal or corrosive environments, materials that resist chemical attack.
Data Centres and Large Commercial Buildings
In facilities with high concentrations of power cables and high available fault currents, cable cleats are required on power distribution circuits. In these environments, they are often used alongside cable glands and cable lugs as part of a complete and compliant cable termination and support system.
Types of Cable Cleats
Cable cleats come in several material types and configurations. Understanding the options helps you select the right product for the installation environment and the cable configuration.
PVC and Polyethylene Cable Cleats (Single Bolt)
These are the most economical type of cable cleat and are widely used in standard indoor and protected outdoor installations. They are manufactured from linear low-density polyethylene (LLDPE) or polypropylene, both of which offer:
- Good chemical resistance to oils, solvents, and common industrial chemicals
- UV resistance for outdoor use
- Low smoke and fume emission in the event of a fire
- A self-adjusting overlapping design that accommodates a range of cable diameters within a single size
- Temperature performance from below freezing to 85°C
Single bolt PVC cleats are available in sizes covering cable diameters from 9mm up to 52mm, making them suitable for most standard power and control cable applications. They are quick and straightforward to install with a single fastener per cleat.
Polypropylene double bolt variants extend this range significantly, covering cable diameters from 46mm up to 120mm. The double bolt design provides greater clamping force and stability for larger, heavier cables.
Aluminium Cable Cleats (Trefoil Type)
Aluminium cable cleats are the standard specification for single-core power cable installations and for any application where higher mechanical strength, corrosion resistance, or temperature performance is required. They are manufactured from aluminium alloy (LM6 grade) and offer:
- Operating temperature range from minus 60°C to plus 120°C, making them suitable for extreme environments
- Excellent corrosion resistance without surface coating
- High withstand load capacity for use in high fault current installations
- Trefoil configuration to correctly space and retain three single-core cables
- Available in both single bolt and double bolt fixing configurations
Aluminium trefoil cleats are available in two sub-types. The first is the double bolt trefoil cleat, which covers cable diameters from 15mm to 155mm across eight sizes. The second is the single and double bolt cleat, which covers a very granular range of cable diameters from 24mm to 76mm across 34 individual sizes, offering an unusually precise fit for a wide variety of cable outer diameters.
The fine sizing granularity of the single and double bolt aluminium cleat range matters in practice because a correctly fitted cleat, one that actually grips the cable snugly, performs significantly better under fault conditions than an oversized cleat that is nominally the right size but leaves the cable loose within it.
Material Selection Summary: PVC and polyethylene cleats suit indoor and standard outdoor applications for small to medium cable diameters. Aluminium cleats are the correct choice for single-core power cables, high fault current installations, offshore and industrial environments, and anywhere that requires higher temperature performance or corrosion resistance. |
Understanding the IEC 61914 Standard
IEC 61914 is the international standard that governs cable cleats. It defines the requirements for design, materials, testing, and marking, and it is the benchmark against which cable cleats should be specified and procured.
The key test in IEC 61914 is the mechanical withstand test. This involves applying a calculated load to the cleat and verifying that it retains the cable without failure. The load is derived from the prospective fault current of the installation and the geometry of the cable arrangement. A cleat that passes this test at a given fault current level is rated for use in installations up to that fault current.
The standard defines three retention categories:
- Category A: Light duty retention, suitable for installations where electromagnetic forces are not a significant concern.
- Category B: Medium duty retention for standard power cable installations with moderate fault current levels.
- Category C: Heavy duty retention for high fault current installations such as substations, power generation facilities, and large industrial plants.
When specifying cable cleats, the engineer needs to know the maximum prospective fault current at the point of installation, which is determined from the electrical system design. The cleat is then selected to meet or exceed the required withstand load for that fault current and cable spacing.
Important: Never substitute a cable cleat with a lower withstand rating than specified on the grounds that it fits the cable. The fit and the withstand rating are separate characteristics. A cleat can physically fit the cable perfectly while being entirely inadequate for the fault current level of the installation. |
How to Size a Cable Cleat Correctly
Correct sizing involves two separate but equally important steps: sizing for the cable diameter and sizing for the fault current load. Both must be correct for the cleat to work as intended.
Step 1: Match the Cleat to the Cable Diameter
Every cable cleat has a minimum and maximum cable diameter it is designed to accommodate. The cable must fall within this range for the cleat to grip correctly. You need the overall outer diameter of the installed cable, which is the finished outer diameter of the cable including its outer sheath, not the conductor size.
This information is available from the cable manufacturer’s data sheet. For armoured cables, note that the overall diameter is significantly larger than the core conductor size, because it includes the bedding, armour, and outer sheath in addition to the insulated cores.
When using aluminium single and double bolt cleats, the very tight sizing increments (some as narrow as 1.5mm) allow you to match the cleat very closely to the exact cable diameter. This improves the mechanical grip and the overall performance of the installation.
Step 2: Verify the Withstand Load
Once you have identified cleats that fit the cable diameter, verify that their rated withstand load meets or exceeds the required load for the installation. The required withstand load is calculated from:
- The prospective fault current at the point of installation (in kA)
- The duration of the fault before the protection operates (in seconds)
- The spacing between cable centres (determined by the cable formation and diameter)
The formula used to calculate the electromagnetic force between cables is defined in IEC 61914. Most cleat manufacturers publish selection tools or tables that allow engineers to look up the required withstand load directly from the fault current and cable spacing, without needing to work through the formula manually.
Step 3: Determine Cleat Spacing
Cable cleats must be installed at intervals that are close enough to prevent the cable from deflecting excessively between cleats under fault conditions. The maximum spacing between cleats is calculated based on the withstand load of the cleat, the weight and stiffness of the cable, and the fault force level. This calculation is also covered in IEC 61914 and in the cleat manufacturer’s technical documentation.
A common mistake in practice is to space cleats at convenient intervals based on tray fixing holes or structural supports, rather than at the engineered maximum spacing. If the calculated maximum spacing is 900mm and the cleats are installed at 1200mm intervals, the installation is not compliant regardless of how well the individual cleats are specified.
Cable Cleat Installation: Step by Step
Installing cable cleats correctly is a straightforward process but there are several points where mistakes are commonly made. Here is how a correct installation proceeds.
1. Prepare the Cable Route
Before installing cleats, the cable route should be complete: cable trays, ladder racks, or conduit runs in place and fixed. If cables are being installed in GI conduit systems, the conduit work should be finished before the cable is pulled through. For surface-mounted installations where cleats will be fixed directly to a wall or structural member, mark the fixing positions at the calculated intervals before beginning the cable pull.
2. Pull the Cable
Pull the cable along the route and lay it in its correct position. For trefoil formations, the three single-core cables should be positioned in the correct triangular arrangement before the first cleat is fitted. Using a cable pulling lubricant during the pull reduces friction and protects the cable outer sheath, particularly in long conduit or duct runs.
3. Fit the First Cleat
Start at one end of the run and fit the first cleat at the correct position. For single bolt PVC cleats, the cleat wraps around the cable and the bolt is inserted through the overlapping tabs and tightened onto the fixing surface. For aluminium double bolt trefoil cleats, the base of the cleat is fixed to the tray or support first, then the cable is seated in the cleat and the retaining strap or second half is bolted down.
4. Work Along the Run at Correct Intervals
Work along the cable run, fitting cleats at the calculated maximum spacing intervals. Do not stretch the intervals because a position is awkward or a fixing point is not available. If necessary, add an additional fixing point rather than increasing the cleat spacing beyond the calculated maximum.
5. Check Tightness and Cable Fit
Once all cleats are fitted, check that each one is tightened to the correct torque (refer to the manufacturer’s data sheet for the specified bolt torque), and that the cable sits correctly within the cleat with no visible damage to the outer sheath from overtightening. The cable should be firmly gripped but not deformed.
6. Label and Document
In formal installations, cable cleat positions should be recorded on the as-built drawings and the cleat type, size, and withstand rating should be documented in the installation records. This is important for future maintenance and for any future fault analysis.
Installation Tip: Always handle cables carefully during the pull to avoid scuffing or damaging the outer sheath. A cable sheath that has been abraded or thinned during installation is more vulnerable at that point, and the damage may not be visible once the cleat is fitted over it. |
Trefoil Formation Explained
If you are specifying cable cleats for a three-phase single-core cable installation, you will encounter the term trefoil formation repeatedly. It is worth understanding exactly what this means and why it matters.
Trefoil formation means the three single-core cables are arranged in an equilateral triangle, with each cable touching the other two. When you look at the cross-section, the three cable centres form a triangle with equal sides. The name comes from the resemblance to a three-leaf clover (trefoil).
The reason trefoil formation is used for single-core AC power cables comes back to the electromagnetic forces discussed earlier. In trefoil formation, the electromagnetic forces between the cables are balanced: each cable is attracted or repelled equally by the other two. This balanced arrangement results in lower net forces on each cable compared to flat formation (where the cables are laid side by side in a line), particularly under fault conditions.
Trefoil cable cleats are specifically designed to hold the three cables in this exact arrangement. The cleat geometry positions the cables at the correct spacing, which ensures the force calculations used to specify the cleat remain valid. If the cables are not actually in the trefoil position the cleat was designed for, the force distribution changes and the cleat specification may no longer be appropriate.
For installations involving signal control cables or other multicore cables rather than single-core power cables, trefoil cleats are generally not required because the conductor arrangement within a multicore cable means the electromagnetic forces are already managed within the cable construction itself.
Common Mistakes in Cable Cleat Specification and Installation
Having covered the correct approach, it is useful to highlight the mistakes that appear most frequently in practice.
- Specifying cleats by diameter only without checking the withstand rating: Selecting a cleat that fits the cable but is not rated for the fault current of the installation is one of the most common errors. The cleat may look correct and may pass a visual inspection, but it will fail under a real fault condition.
- Installing cleats at the wrong spacing: Spacing cleats at intervals that are convenient rather than at the calculated maximum spacing leaves the cable unsupported between fixings. Under fault conditions, unsupported cable will deflect and the forces may exceed what the cleats are rated for at the actual spacing used.
- Using cable ties instead of cleats on single-core power runs: Cable ties are not designed or tested for fault current retention. Using them as a substitute for cable cleats on power cable runs is not compliant with IEC 61914 and creates a genuine safety risk.
- Using an oversized cleat: A cleat that is too large for the cable will not grip it properly. The cable can move within the cleat under fault conditions, which can damage the cable sheath and reduce the effective retention force.
- Ignoring environmental requirements: Using PVC cleats in an environment that requires corrosion-resistant aluminium, or failing to specify UV-resistant materials for an outdoor installation, leads to premature degradation of the fixings and a loss of retention performance over time.
- Overtightening: Tightening cleat bolts beyond the specified torque can deform the cable sheath or damage the cleat itself. Always use a torque wrench and refer to the manufacturer’s specification.
A Practical Cable Cleat Selection Summary
To bring the sizing and selection process together into a usable reference, here is the logical sequence to follow when specifying cable cleats for a new installation.
- Identify the cable type and outer diameter: Get the finished overall diameter from the cable data sheet. For armoured cables this includes the armour and outer sheath.
- Determine the cable formation: Single-core cables in trefoil or flat formation require trefoil cleats. Multicore cables use standard single-cable cleats.
- Establish the prospective fault current: This comes from the electrical system design. It is the maximum fault current available at the point where the cable is connected.
- Calculate the required withstand load: Use the IEC 61914 formula or the manufacturer’s selection table to find the required withstand force based on fault current and cable spacing.
- Select the cleat with matching diameter range and sufficient withstand rating: The cleat must satisfy both criteria independently.
- Calculate the maximum installation spacing: Refer to the manufacturer’s spacing tables for the selected cleat and the cable weight per metre.
- Select the correct material for the environment: PVC or polypropylene for standard indoor or protected applications. Aluminium for industrial, outdoor, offshore, or high-temperature environments.
The full range of cable cleats from Raiden covers PVC single bolt, polypropylene double bolt, and aluminium trefoil types, with the technical sheets for each product providing the diameter ranges, withstand loads, and dimensional data needed to complete this selection process.
Frequently Asked Questions
1. Do I need cable cleats for multicore armoured cables?
For fixed armoured multicore cables, standard cable clips or saddles providing support at appropriate intervals are often sufficient because the armour construction already provides significant mechanical protection and the balanced core arrangement within the cable limits electromagnetic forces. However, where the installation is subject to vibration, is in a critical circuit, or where the specific project specification requires it, cable cleats are still used. Check the project specification and the relevant installation standard for the sector.
2. Can I use the same cable cleat for different cable diameters?
Only if the cable diameter falls within the manufacturer’s stated range for that cleat. The self-adjusting overlapping design of PVC single bolt cleats does accommodate a range of diameters within one size. For aluminium cleats, the sizing is more precise: always verify the specific cable outer diameter against the cleat’s minimum and maximum diameter range.
3. How often should cable cleats be inspected?
In normal installations, cable cleats should be visually inspected as part of any routine electrical installation inspection. Check for physical damage, loosening of fixings, corrosion of metallic components, and any sign of cable sheath damage at the cleat contact points. In harsh environments such as offshore or industrial settings, inspection intervals should be shorter and more systematic.
4. What is the difference between single bolt and double bolt cleats?
Single bolt cleats are simpler and quicker to install, and are suitable for light to medium-duty applications. Double bolt cleats provide a stronger and more stable fixing, particularly for larger and heavier cables. They are the standard choice for trefoil installations and for cables in high fault current environments.
5. Do cable cleats work with rubber flexible cables?
Cable cleats are primarily designed for fixed cable installations. H07RN-F rubber flexible cables are typically used in portable or temporary power applications where the cable is regularly moved, coiled, or handled, and where fixed cleats are not the appropriate support method. If a rubber flexible cable is installed in a fixed route that requires mechanical retention, cleats can be used, but this is not the typical application.
Why Proper Cable Cleat Selection and Installation Matters
Cable cleats are small components with a significant engineering purpose. They are the product that keeps power cables in place when the worst happens, and getting the specification right matters in a way that goes beyond neatness or good practice.
The process is methodical: know your cable diameter, know your fault current, calculate the required withstand load, select a compliant cleat, and install at the correct spacing. Each step builds on the previous one, and skipping or estimating any of them introduces risk that is not visible until a fault occurs.
Understanding how cable cleats fit into a complete cable management and termination system is useful background for any installation. The guides on cable glands, cable lugs, and cable ties cover the other components that work alongside cable cleats in a properly assembled cable run. And if you are working with signal or control cables on the same project, the guide to signal cables explained provides useful context on how those cable types differ in their support and installation requirements.