BS 5467 vs BS 6724 vs BS 6346: UK Low-Voltage Armoured Cables Compared — the Questions Engineers Ask

If you build or quote low-voltage armoured cables for the UK, Ireland, the Gulf or many Commonwealth markets, three British Standards keep appearing in specifications: BS 5467, BS 6724 and BS 6346. All three describe armoured LV power cables, all three cover the familiar 600/1000 V and 1900/3300 V ratings, and on a drawing the cables look almost the same. The differences sit in the insulation, the bedding and the oversheath — and those differences decide where each cable may be installed, how much current it carries and what it costs.

This comparison of the UK low-voltage armoured cables BS 5467, BS 6724 and BS 6346 is built around the questions design engineers and estimating teams actually ask. It summarises how the standards think; it does not replace them, and it deliberately avoids reproducing their tables.

What are BS 5467, BS 6724 and BS 6346 for?

All three standards describe complete armoured cables for fixed installations: sub-mains and distribution circuits in buildings, industrial plants, infrastructure, outdoor routes and direct burial. They fix the construction family, the permitted materials, the rated voltages and the tests that prove the cable.

• BS 5467 — armoured cables with thermosetting (XLPE) insulation and a PVC bedding and oversheath. This is the classic "XLPE/SWA/PVC" cable and the default choice for most general-purpose LV armoured circuits.
• BS 6724 — the same thermosetting insulation and armour, but with low-smoke, halogen-free bedding and oversheath. It is the "XLPE/SWA/LSZH" cable for buildings and enclosed spaces where smoke and corrosive gases would endanger people or equipment.
• BS 6346 — armoured cables with PVC insulation and PVC bedding and oversheath: the older "PVC/SWA/PVC" family.

The same logic exists one voltage class up, where BS 6622 and BS 7835 split armoured MV cables into a general-purpose and a low-smoke halogen-free family.

Does the standard tell you how to build the cable?

Largely, yes. Like IEC 60502-1, these British Standards are construction standards: they describe the layers, the materials and their minimum dimensions, and they define the core combinations in each family, from two-core power cables to multicore auxiliary cables. Conductors follow BS EN 60228 — see our explanation of why conductor size is defined by resistance.

What the standards do not decide is the installation: the current a cable may carry on a particular route (in the UK usually sized to BS 7671, elsewhere often with the IEC 60287 method), whether the armour is enough as a protective conductor, or which fire classification the building requires. Those answers come from the installation design and the project specification.

Why is BS 5467 more common than BS 6346 today?

The difference is the insulation. XLPE is a thermoset: it is crosslinked and does not soften when heated in the way PVC does. That allows a maximum continuous conductor temperature of 90 °C for XLPE, against 70 °C for PVC-insulated cables.

The practical consequences:

• For the same conductor size, a BS 5467 cable carries noticeably more current than a BS 6346 cable in the same installation.
• Or, for the same load, a BS 5467 cable can often be one conductor size smaller — less copper or aluminium, a smaller diameter, lighter drums, smaller glands.
• XLPE also tolerates short-circuit heating better, which matters for fault ratings.

This is why BS 6346 is now mostly seen in like-for-like extensions of existing installations or older specifications. For new designs, BS 5467 is usually the cheaper cable per ampere.

Can BS 6724 replace BS 5467 — and the other way round?

As with the MV pair, the answer is not symmetrical.

BS 6724 instead of BS 5467 is usually acceptable electrically: insulation and armour follow the same logic, so current ratings for the same installation are essentially the same. But it is not automatically the better offer. Halogen-free compounds are more expensive, generally less tough mechanically, and less suited to permanently wet or aggressive environments than PVC. A designer who specified BS 5467 for a buried or outdoor route may reject an LSZH alternative on durability grounds.

BS 5467 instead of BS 6724 is almost never acceptable. If the specification asks for low smoke and low acid-gas emission — public buildings, hospitals, schools, transport, data centres, high-rise residential — a PVC-sheathed cable fails the very property the purchaser cared about.

Projects often use both: BS 5467 outside and buried, BS 6724 inside the building — two cable types on what the client sees as one circuit, which the design, BOM and drum schedule must reflect.

Is a BS 6724 cable fire resistant?

No. This is the most frequent misunderstanding in LV tenders. BS 6724 cables are designed to limit flame spread, smoke and corrosive gas when they are involved in a fire. They are not designed to keep a circuit working during a fire.

Circuit integrity is a separate property with separate test methods. For armoured LV cables in the UK it is covered by BS 7846, which CablePLM also supports. If a tender lists fire pumps, smoke extraction, sprinklers or other life-safety circuits, the cable for those circuits needs a fire-resistance requirement in its own right; "LSZH" in the specification does not answer it. Our comparison of PVC, XLPE, EPR and LSZH explains why the materials behave so differently in fire.

Which tests prove the difference?

All three share the usual structure of routine, sample and type tests covering conductor resistance, voltage withstand, dimensions and material properties.

BS 6724 adds the fire-behaviour evidence: flame propagation, smoke density and the acidity and corrosivity of combustion gases, assessed with the familiar IEC/EN test families (IEC 60332, IEC 61034 and IEC 60754 and their EN equivalents). For a manufacturer the consequence is simple: changing the bedding or oversheath compound, or its supplier, can invalidate existing fire-test evidence even when nothing electrical has changed.

For cables permanently installed in UK and EU buildings, the project may also require a reaction-to-fire classification under the construction products regime — a separate layer of evidence on top of the product standard.

Insight: armour type follows the number of cores

The physics is the same as for MV cables:

• Multicore cables are normally armoured with galvanised steel wire (SWA). The magnetic fields of the cores largely cancel, so steel armour causes no significant losses.
• Single-core cables for AC circuits use non-magnetic aluminium wire armour (AWA). Steel around a single AC conductor would heat up through induced currents and magnetic losses and reduce the current rating.

A tender line that says "single-core SWA" for an AC sub-main is almost always an error worth querying before pricing.

Insight: the armour is often the protective conductor

In UK practice the steel wire armour of BS 5467 and BS 6724 cables is frequently used as the circuit protective conductor. Whether that is acceptable depends on the armour cross-section, the fault current and the disconnection time of the protective device — an installation calculation, not a property of the standard. Where the armour is not enough, the designer adds a separate earth conductor or chooses a cable with an extra core. Either way, the decision changes the construction and the price, so it should be settled at tender stage.

How do the three standards compare?

Typical tender mistakes

1. Treating BS 6724 as "BS 5467 with a different sheath" and pricing it the same.
2. Offering BS 6346 where BS 5467 is specified, or sizing a BS 5467 alternative with PVC ratings.
3. Confusing LSZH with fire resistant on life-safety circuits.
4. Steel wire armour on single-core AC cables.
5. Assuming the armour is adequate as the protective conductor without checking the fault data.
6. Missing the reaction-to-fire classification or other project additions such as UV resistance, anti-termite sheaths or specific sheath colours and marking.

Tender checklist for BS 5467, BS 6724 and BS 6346 cables

Before designing, confirm:

1. Which standard applies to which part of the installation, and whether alternatives are accepted.
2. Rated voltage: 600/1000 V or 1900/3300 V.
3. Conductor material, size and number of cores, including any separate earth core.
4. Single-core or multicore, and the armour type that goes with it.
5. Whether the armour is used as the protective conductor, and the fault data to check it.
6. Fire requirements: low smoke and acid gas, a reaction-to-fire class, or circuit integrity to BS 7846.
7. Installation conditions for the current rating: method, grouping, ambient and ground temperature.
8. Sheath additions, colour and marking.
9. Which existing type tests, including fire tests, cover the offered design.

How CablePLM handles BS 5467, BS 6724 and BS 6346

In CablePLM, BS 5467, BS 6724 and BS 6346 are separate calculation methods in the standards library, alongside BS 7846, BS 7889 and IEC 60502-1. You choose the core group, conductor, insulation, armour and sheath; CablePLM builds the cable layer by layer — see our layer-by-layer anatomy of a power cable — and generates the bill of materials, IEC 60287 current ratings, short-circuit capability of conductor and armour, and both the engineering and customer versions of the datasheet. Every value is marked as standard data or as an estimate, so reviewers can see where a number comes from.

For tenders that mix several standards on one project, the Tenders & Projects add-on keeps each cable type linked to its specification clause, Cable Selection & Optimization helps compare XLPE and PVC options for the same load, and Qualification & Quality shows which designs are already covered by your electrical and fire type tests.

Want to see your UK LV armoured cable range designed this way? Book a demo.