Recommendations for Heavy-Duty Cable Clamps Capable of Supporting Multiple Large Cables

When you’re routing multiple large-diameter cables through an energy, industrial, offshore, or rail installation, the fastening system you choose is not a minor detail. It’s the component standing between a safe, stable installation and a costly failure. If a clamp can’t withstand the electromagnetic forces generated during a short circuit, cables break loose, insulation is damaged, and fire risk increases sharply. Possibility of human injury or death.  For installations carrying several large cables at once, that risk is multiplied. This guide walks through which heavy-duty cable clamp types are actually built to handle multiple large cables, what separates a genuinely heavy-duty clamp from a standard one, and why KOZ Products’ certified range is worth considering for your next project. 

Why standard clamps aren’t enough for multiple large cables 

During a short circuit, the electromagnetic forces between conductors can reach as high as 50 kilonewtons. That’s not a theoretical figure it’s the kind of dynamic load a fastening system must survive without releasing its grip. A clamp that isn’t rated and tested for this scenario may hold cables in place under normal conditions but fail exactly when it matters most. This is why cable ties, standard brackets, and uncertified clamps are not appropriate for high-voltage or multi-cable installations: they’re designed for temporary bundling, not for holding multiple large conductors securely through a fault event. 

The safest approach is to specify clamps certified to the international NEN-EN-IEC 61914:2021 standard, which requires a clamp to hold cables in place for five complete short-circuit cycles without loosening. This certification also covers temperature extremes, salt water exposure, impact resistance, and UV aging — all relevant to real-world heavy-duty installations, whether indoors in a switch room or outdoors on an offshore platform. 

Top recommendations for multiple large cables 

Based on both the demands of heavy-duty installations and the range currently available on the market, three clamp types stand out for supporting multiple large cables: 

1. Single ST series — the foundational clamp for large, single-conductor cables

The Single ST series is the base of the heavy-duty range, covering an exceptionally wide diameter span from 11mm up to 160mm, with a two-part design and clamping forces reaching up to 85 kN on the larger types. It’s the clamp to reach for first when several large individual cables need to be secured side by side rather than bundled together: because each ST clamp is rated on its own for maximum holding force, installing one per cable gives every conductor independent, full-strength protection against short-circuit forces, rather than sharing load across a shared bracket. With two mounting holes and a slim two-piece shell, it also installs quickly on cable trays, walls, or racks, making it a practical starting point for any multi-cable, high-voltage layout. 

2. Trefoil TRI series — for three-cable, high-load configurations

The Trefoil TRI series is purpose-built for securing three cables together in a triangular formation, with a nominal outer diameter range from 15mm up to 150mm. This is one of the widest diameter ranges available in a certified trefoil clamp, making it a strong recommendation for large power cables bundled in a three-phase configuration. The TRI version is designed with two mounting holes for heavy-duty applications requiring maximum performance, while the lighter TRI ECO variant offers a more cost-effective option without compromising the safety rating. Both include a central mounting hole as an additional fixing option, and the trefoil shape itself helps maintain electromagnetic balance, which matters in dynamically loaded, short-circuit-intensive environments. For large three-phase cable runs in energy or industrial settings, this is typically the first series worth specifying. 

3. Square series — for four large cables in one clamp

Where an installation needs to fasten four single or multiple-conductor cables together, the Square series is designed specifically for that configuration, rated for cables with a nominal outer diameter between 25mm and 38.5mm. It’s a compact solution where installation space is limited but four large cables still need to be held securely as a single, stable unit. This series is a practical recommendation anywhere four parallel large cables need to be grouped without the footprint of four separate single clamps. 

4. Universal UNI TRI series — for the highest cable density

For installations that need to secure far more than three or four large cables at once, the Universal UNI TRI series is the standout recommendation. It allows nine or twelve cables to be clustered together in a compact trefoil arrangement (3×3 or 4×3 per layer), which saves significant space while keeping every cable properly restrained. The related UNI clamp uses a single housing that forms both the top and bottom shell, making it well-suited to cables mounted side by side or stacked in layers, and additional layers can be added without dismantling the existing setup. For substations, switch rooms, or any installation where cable density is high and space is at a premium, this modular design offers a genuinely scalable heavy-duty solution. 

5. Universal UNI TRI series — for the highest cable density

For installations that need to secure far more than three or four large cables at once, the Universal UNI TRI series is the standout recommendation. It allows nine or twelve cables to be clustered together in a compact trefoil arrangement (3×3 or 4×3 per layer), which saves significant space while keeping every cable properly restrained. The related UNI clamp uses a single housing that forms both the top and bottom shell, making it well-suited to cables mounted side by side or stacked in layers, and additional layers can be added without dismantling the existing setup. For substations, switch rooms, or any installation where cable density is high and space is at a premium, this modular design offers a genuinely scalable heavy-duty solution. 

What makes these clamps heavy-duty in practice 

The classification “heavy-duty” only means something if it’s backed by testing, not just a product label. KOZ Products’ clamps are manufactured from black, glass-fibre reinforced polyamide (PA66), a material chosen for its mechanical strength, chemical resistance, and long-term stability under load. This material is: 

• Resistant to oils, greases, salt water, ozone, acids, alkalis, fuels, and aggressive chemicals 

• Rated for permanent use from -80°C to +120°C, with short-term peaks up to +220°C 

• Self-extinguishing according to UL 94 V-0, and halogen-free 

• Non-conductive, non-magnetic, and free of sharp edges 

Every clamp in the range is certified to NEN-EN-IEC 61914:2021, with testing carried out at accredited laboratories including KEMA (DNV-GL), SGS, Schneider Electric, UL, and KU Leuven. For marine applications, the range also carries Lloyd’s Register Type Approval, and for rail applications, EN 45545-2 classification. That combination of independent, third-party testing is what distinguishes a genuinely heavy-duty clamp from one that simply looks robust. 

Where these heavy-duty clamps are used 

KOZ Products’ cable clamps and cable blocks, spanning a diameter range of Ø11mm to 160mm, are applied in more than 60 countries and have been developed since 1998. Six core product categories cover roughly 95% of professional installation needs without requiring a custom solution, and they’re used across: 

• Energy infrastructure, where large power cables must be securely restrained against short-circuit forces for the lifetime of the installation. 

• Offshore platforms, where salt water resistance and long-term corrosion resistance are non-negotiable. 

• Railways, where EN 45545-2 fire safety classification is required for cable fastening in rolling stock and infrastructure. 

• Industrial and data centre environments, where high cable density and short-circuit protection are both critical to uptime and safety. 

• Data center environments, where non-conductive, non-magnetic clamps keep dense, high-value cable runs organized and securely restrained without introducing any risk of interference or short-circuit exposure to nearby sensitive electronic equipment. 

Why choose KOZ Products for a multi-cable, heavy-duty installation 

Beyond the technical certifications, a few practical factors make this range a strong recommendation for projects involving multiple large cables: 

• A complete size range: with clamps spanning Ø11mm to 160mm across single, trefoil, square, universal, and specialised series, most projects can be fully specified from a single supplier rather than mixing certified and uncertified components. 

• Verified, not just claimed, performance: independent testing from KEMA, SGS, Schneider Electric, UL, and KU Leuven means the short-circuit resistance, temperature range, and chemical resistance figures are backed by third-party accreditation. 

• Global track record: with cable clamps in use across more than 60 countries since 1998, the range has a long operational history in demanding, real-world conditions. 

• Custom solutions when needed: for atypical cable configurations or project-specific requirements that fall outside the standard series, custom-engineered clamps and cable blocks are available. 

Installation efficiency and long-term value 

Heavy-duty doesn’t have to mean difficult to install. The two-piece and modular designs used across the ST Trefoil, Square, and Universal series are built for straightforward on-site assembly, with a specified initial fastening torque of 5-8 Nm for the mounting hardware. This matters on large projects: installers working with dozens or hundreds of clamps benefit from a system that’s fast to fit correctly the first time, rather than one that requires special tools or repeated adjustment. The modular nature of the Universal UNI TRI series in particular means additional cable layers can be added later without dismantling the existing installation, which reduces both labor time and the risk of disturbing cables that are already correctly seated. 

There’s also a cost dimension beyond the purchase price. A clamp that fails during a short circuit doesn’t just need replacing — it can mean damaged insulation, damaged adjacent equipment, unplanned downtime, and in the worst case, fire damage or safety incidents. Weighing the price of a certified heavy-duty clamp against the potential cost of an uncertified one failing under load makes the case fairly straightforward for any installation carrying multiple large, high-value cables. On top of that, the range comes with a lifetime warranty, reinforcing that these clamps are built to remain reliable for the operational life of the installation, not just through initial commissioning and testing. 

FAQ 

Which cable clamp is best for holding multiple large power cables together? 

For three large cables in a trefoil configuration, the Trefoil TRI series (15-150mm) is the strongest heavy-duty recommendation. For four cables, the Square series (25-38.5mm) is purpose-built for that exact configuration. For higher cable counts, the Universal UNI TRI series clusters nine or twelve cables per layer. 

How do I know if a cable clamp is genuinely rated for heavy-duty use? 

Look for certification to NEN-EN-IEC 61914:2021, with test results from recognized accredited laboratories. A clamp rated for heavy-duty use should be documented to withstand at least five short-circuit cycles without loosening, along with defined temperature, salt water, and UV resistance figures. 

Can these heavy-duty clamps be used outdoors and offshore? 

Yes. The PA66 material used across the range is UV-resistant, salt water-resistant, and operates across a wide temperature range, and Lloyd’s Register Type Approval confirms suitability for marine applications. 

What’s the difference between the Trefoil TRI and TRI ECO versions? — same certification and diameter range, TRI is built for maximum load, TRI ECO is the lighter, more cost-effective option. 

Do heavy-duty cable clamps need re-torquing or maintenance after installation? — maintenance-free once installed at spec, backed by a lifetime warranty, with routine visual inspection still good practice. 

Ready to specify the right clamps for your project? 

Choosing the right heavy-duty cable clamp for multiple large cables comes down to matching the cable count and diameter to a certified, tested series, rather than defaulting to whatever is available locally. If your project involves several large cables and you want tested, certified confidence rather than guesswork, KOZ Products’ technical specialists can advise on the right series for your configuration or prepare a competitive quote based on your project’s specifications.