📌 BS 6724 (LSZH Armoured): Complete Guide — Specification, Uses & Advantages

In modern electrical installations, safety, performance, and regulatory compliance are essential. One cable that ticks all these boxes is the BS 6724 (LSZH Armoured) cable — a British-standardised, low-smoke zero-halogen armoured cable widely used for power distribution and mains wiring in buildings, industrial facilities, and public infrastructure.

Whether you’re a contractor, engineer, or buyer, this guide will help you understand everything about BS 6724 LSZH Armoured cables — from their construction and standards to where and why they’re used.

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🔎 What Is BS 6724 Cable?

BS 6724 cable refers to a class of armoured power cables manufactured to meet the requirements of British Standard BS 6724. These cables are designed for low voltage electrical installations where mechanical protection and reduced smoke & toxic gas emissions are priorities.

In simple terms, BS 6724 cable is:

✔ Armoured for mechanical protection
✔ Insulated with XLPE (Cross-Linked Polyethylene)
✔ Sheathed in LSZH (Low Smoke Zero Halogen) compound
✔ Suitable for a wide range of applications — indoors, outdoors, buried underground, and in ducts.

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🧱 Key Components of BS 6724 (LSZH) Armoured Cable

Understanding the construction helps explain why this cable is so reliable:

📍 1. Conductors

• Usually made from annealed stranded copper (Class 2) for excellent conductivity and flexibility.
• Sizes range from small cores (1.5mm²) to large power feeds (hundreds of mm²).

📍 2. Insulation

• The base insulation is typically cross-linked polyethylene (XLPE) — durable, high temperature tolerant, and suitable for electrical stress at 0.6/1 kV ratings.

📍 3. Armour

• Single-core cables use Aluminium Wire Armour (AWA) — non-magnetic and stops electrical losses due to induced currents.
• Multi-core cables usually have Galvanised Steel Wire Armour (SWA), providing strong mechanical protection against cuts, impacts, rodents, and ground pressure.

📍 4. LSZH Sheath

• Sheathed with a Low Smoke Zero Halogen compound, which emits minimal smoke and no toxic halogen gases if exposed to fire — a critical safety feature in public spaces.

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🔌 What Does LSZH Mean and Why Is It Important?

LSZH stands for:

✨ Low Smoke — produces very little smoke
✨ Zero Halogen — no halogenated materials (like PVC) that emit toxic gases

In fire conditions, traditional PVC cables can emit thick black smoke and harmful gases (e.g., hydrogen chloride) that can incapacitate people and damage equipment. BS 6724 LSZH cables dramatically reduce these risks, making evacuation and emergency response safer.

This is especially relevant for:

• Airports and train stations
• Hospitals and schools
• High-rise buildings
• Data centers
• Tunnels and metro systems
• Power stations
  All of these environments may see high foot traffic or house sensitive electronics where fire safety is non-negotiable.

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📊 Standards and Fire Performance

BS 6724 armoured LSZH cables are not just mechanically robust — they’re tested against rigorous electrical and fire safety standards:

📌 Industry Standards Include:

• BS 6724 — primary standard for LSZH armoured cables
• BS EN 50267 / IEC 60754-1 — halogen gas emission tests
• BS EN 50268 / IEC 61034 — smoke emission tests
• IEC 60332 — flame propagation tests
• Construction Products Regulation (CPR) compliance (minimum classes apply)

These standards ensure the cable doesn’t just physically withstand fire — it performs safely under fire conditions with controlled smoke and gas outputs.

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🏭 Where BS 6724 LSZH Armoured Cables Are Used

Due to their safety and performance features, these cables are preferred in sectors like:

🏢 Commercial and Institutional Buildings

Power distribution in multi-story offices, auditoriums, and public venues.

🏥 Healthcare and Educational Facilities

Reduced toxic smoke protects vulnerable populations and critical equipment.

🚇 Transport Infrastructure

Stations, tunnels, and terminals where fire safety regulations are strict.

⚙️ Industrial and Utility Installations

Manufacturing plants, refineries, and utility installations that require durable and compliant cable runs.

🌳 Underground and External Installations

BS 6724 cables can be directly buried or installed in ducts where mechanical risk or fire threats exist.

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🤔 BS 6724 vs Other Armoured Cable Standards

Comparing BS 6724 to other cable types highlights its strengths:

📌 BS 6724 vs BS 5467 (PVC Sheath)

• BS 6724 LSZH emits minimal smoke & no halogen gases.
• BS 5467 (PVC) emits thick smoke and toxic gases in fires.
• BS6724 is often a direct safe replacement for BS 5467 where fire safety is required.

📌 LSZH vs PVC

• LSZH is safer in life-critical environments, while PVC may be cheaper but less safe under fire conditions.

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💡 Installation & Best Practices

Proper installation adds safety and longevity:

✔ Ensure correct cable glands for armoured cables
✔ Follow manufacturer bending radius guidelines — typically 6 to 8× overall diameter depending on core size.
✔ Use in accordance with electrical wiring regulations (e.g., BS 7671 in UK)
✔ Ensure jointing and terminations are compatible with LSZH and armour type

Always rely on certified electricians to install these cables safely and legally.

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📈 Benefits of Choosing BS 6724 LSZH Armoured Cables

🔹 Enhanced Safety

Minimises smoke and toxic gases — crucial in fire emergencies.

🔹 Reliable Mechanical Protection

Armoured design withstands impact, crushing, rodents, and ground conditions.

🔹 Versatile Applications

Suitable indoors, outdoors, and underground.

🔹 Regulatory Compliance

Meets British Standards and international safety test requirements.

🔹 Long-Term Performance

XLPE insulation provides thermal stability and electrical strength.

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🛒 Final Thoughts

The BS 6724 (LSZH Armoured) cable is not just another power cable — it’s a safety-driven, compliant, and durable solution for modern electrical infrastructure. Whether you’re upgrading installations or planning new builds, understanding and choosing BS 6724 ensures that safety and performance are built into your project from the ground up.

For engineers, contractors, and specifiers, this cable represents best-practice compliance with modern electrical safety standards — safeguarding life, property, and critical systems in both everyday operations and emergency conditions.

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