BS 5467 vs BS 6724: PVC or LSZH, and the CPR Class It Sets

01Two standards, one cable: what actually changes

When a specification asks for "BS 5467 or BS 6724", it is not asking for two different products. It is asking which of two fire behaviours the installation needs. Reading the construction from the conductor outward, the two standards share every layer except two.

• Conductor — plain annealed copper, Class 1 solid or Class 2 stranded, circular up to roughly 25–35 mm² and shaped (sectoral) above that; solid aluminium Class 1 as an alternative.
• Insulation — cross-linked polyethylene, type GP8 to BS 7655 in the common build, giving 90 °C continuous and a 250 °C short-circuit allowance.
• Bedding (inner sheath) — this is the first changed layer. PVC under BS 5467, an LSZH compound under BS 6724. Its job is to keep the laid-up cores circular and to stop the armour damaging the insulation.
• Armour — a single layer of galvanised round steel wire on multicore cables, plain aluminium wire on single-core. Same in both standards.
• Oversheath — the second changed layer. PVC again under BS 5467; LSZH again under BS 6724.

That is the whole difference. Both are rated for indoor, outdoor, tray, duct and direct-burial installation in free-draining soil, and both are properly described as "armoured mains" or "booklet armoured" cable in the UK market. The trap is treating the two type strings as interchangeable when the project's fire strategy has already picked one of them.

02BS 5467: the PVC-sheathed armoured family

BS 5467 is Electric cables — Thermosetting insulated, armoured cables of rated voltages of 600/1 000 V and 1 900/3 300 V for fixed installations. Its scope covers construction, testing and performance requirements for armoured cables with thermosetting insulation, for fixed installation in industrial areas, buildings and similar applications. The current edition is BS 5467:2016, which came into effect on 30 April 2016 and incorporates a corrigendum; the previous edition, BS 5467:1997+A3:2008, was withdrawn on the same date. A datasheet that still cites the 1997 edition is quoting a document that has not been current for a decade.

The standard fixes the family rather than a single product. It specifies the number of cores — single, two, three, four and five-core power cables, plus auxiliary multicore cables at 7, 12, 19, 27, 37 and 48 cores — the type of conductor (plain annealed stranded copper, or solid aluminium), and colour-coded or number-coded core identification. Core colours follow the familiar sequence: brown or blue on single-core; brown and blue on two-core; brown, black and grey on three core; brown, black, grey and blue on four core; green/yellow plus brown, black, grey and blue on five core; white cores with printed numbers at six cores and above.

Two construction rules matter when a datasheet is checked against the standard. The first is the armour split: multicore cables use steel wire armour (SWA), single-core cables use aluminium wire armour (AWA). The second is that the bedding under the armour is a PVC layer, and the oversheath above it is PVC again. That is the construction the UK market writes as CU/XLPE/SWA/PVC for multicore and CU/XLPE/AWA/PVC for single-core.

03BS 6724: the same cable in a low-smoke sheath

BS 6724 is the low-emission member of the family: Electric cables — Thermosetting insulated, armoured cables of rated voltages of 600/1 000 V and 1 900/3 300 V for fixed installations, having low emission of smoke and corrosive gases when affected by fire. The construction recipe is the one described above, with the bedding and the oversheath both extruded in a low-smoke halogen-free compound instead of PVC. The cable is designed to have improved fire performance when installed in air, and is expected to be used primarily in such locations, though it remains suitable for direct burial in free-draining soil — but not in waterlogged ground or ground subject to flooding.

Because the scope is written around a fire property, BS 6724 also has to bound the product more tightly than BS 5467 does. The published range is explicit:

Scope-level range as published by the standard's scope summary. Individual manufacturers publish their own section ranges and approvals; the library holds no BS 6724 text, so no clause number or standard table value is quoted here.

The material change buys three measurable properties. The compound is halogen-free, so it does not release hydrogen chloride; the hydrogen chloride emission is quoted at not more than 0.5 %. It is low-smoke, with a light transmittance of at least 60 % under the 3-metre cube smoke test, against the dense black smoke of a burning PVC. And it passes a bunched flame test in addition to the single-cable vertical test that BS 5467 carries — the difference between "this one cable will not sustain a flame" and "a tray full of these cables will not propagate one". That is the entire reason a designer reaches for BS 6724: not a better cable, a better fire outcome in an enclosed or public space.

04The side-by-side comparison

Read this as two descriptions of one cable. Every row except the bedding, the sheath and the fire behaviour is common to both standards.

Compiled from the published scope of both standards and two independent supplier references. The IEC naming row reflects the naming convention used internationally for the same constructions; it is not a clause of either British standard. No standard table value or clause number is quoted.

05The published dimensional and ampacity range

Because the two builds share the conductor, the insulation thickness and the armour, a 4-core cable of a given cross-section comes out at essentially the same size and carries the same current whichever sheath it has. The table below is one manufacturer's published data for both versions, so the two can be compared directly.

One manufacturer's published datasheet range for 4-core copper Class 2 cable at 0.6/1 kV, bending factor 8×OD, operating range −20 to +90 °C. The two versions are printed side by side where both are published; larger PVC sizes are shown alone because the LSZH range in this dataset stops at 120 mm². These are one manufacturer's values, not standard table values — treat them as indicative and verify against the datasheet for the exact build you are buying.

06The CPR class, and why the standard name does not set it

For cables used in fixed installations in buildings, the fire question a European buyer actually asks is not "PVC or LSZH" but "what class is it?". That question is answered by the Construction Products Regulation and its classification standard, not by BS 5467 or BS 6724. A cable is tested as a finished product and declared in one of the reaction-to-fire classes runs from Aca down to Fca, with additional sub-classes for smoke production (s1–s3), flaming droplets (d0–d2) and acidity (a1–a3).

Because the sheath is what burns, the two builds tend to land in different classes. In the manufacturer range held for this page, every 4-core PVC cable is declared Eca and every LSZH cable Dca-s1,d2,a1 — same conductor, same insulation, same armour, one class apart on the fire ladder and with the smoke, droplet and acidity sub-classes declared only on the LSZH product.

07Mapping to GB/T 12706.1 and IEC 60502-1

The same physical cable appears under a third naming system in China. GB/T 12706.1-2020 is the Chinese standard for extruded-insulation power cables at 1 kV (Um = 1.2 kV) and 3 kV (Um = 3.6 kV), and its relationship to the international document is fixed on its own cover: it is modified from IEC 60502-1:2004 — the adoption code is MOD, not IDT. So the Chinese standard, the IEC standard and the two British standards describe one product family on the same conductor and insulation basis, while remaining four separate documents.

The Chinese designation encodes the same layers in a compact string. YJ is the cross-linked polyethylene insulation; the letter after it is the oversheath (V for PVC, Y for polyethylene); L marks an aluminium conductor and is omitted for copper; and the trailing digits give the armour — 22 for double steel tape, 32 for fine round steel wire, 42 for coarse round steel wire. A halogen-free armoured variant takes the WDZ- prefix ahead of the same layer letters and armour digits.

That mapping is where a buyer has to be careful, because the armour types do not line up one to one:

The Chinese type codes follow the product-designation logic in the GB/T 12706.1 annex; the armour digit meanings (22 / 32 / 42) are as published on our YJV product page. The library holds the GB/T 12706.1 cover, contents and scope but not its numeric tables, so no clause number or standard table value is quoted.

08Four things that do not translate

1. The two standards are not interchangeable approvals

BS 5467 and BS 6724 describe comparable constructions, but they are separate documents with separate scopes. A cable made and tested to one is not thereby made and tested to the other, and changing a PVC sheath to LSZH moves the product into different testing territory — bunched flame, halogen and smoke tests that the PVC build is not required to pass. If the project names BS 6724, evidence against BS 5467 does not answer it.

2. Steel armour on a single-core AC cable is a design error

Single-core cables in both standards use aluminium wire armour, for the magnetic reason set out above. A datasheet offering a single-core steel-wire-armoured construction without addressing induced heating is describing a cable that will derate or overheat. Note also that "AWA" is sometimes mis-expanded as "single wire armour" — it stands for aluminium wire armour, and the mix-up hides which conductor-material family the armour belongs to.

3. The CPR class is a property of the tested product

Neither standard number carries a CPR class. The class comes from testing the finished cable, and it can differ between two builds that both claim the same standard number, and between two manufacturers building to the same standard. A declaration of performance is the document that names it.

4. The minimum installation temperature is not common across datasheets

Sources for the LSZH build disagree here, and it is worth knowing before a winter installation is planned. One standard scope summary quotes a minimum installation temperature of −15 °C for BS 6724; the manufacturer datasheets held for this page quote 0 °C for both the PVC and the LSZH build at the same cross-sections. The two figures are not reconciled in this article — use the value on the datasheet for the exact cable you are installing, and re-check it against the site condition.

09What this page publishes, and what it will not

The layer table, the scope ranges and the dimensional data above come from the published scope of both standards and from named manufacturer datasheets, all listed in Sources. Where a document was not available, the page stops at the standard name: neither British standard's numeric tables are quoted, no clause number is given, and the CPR classes are presented as one manufacturer's declarations rather than as a property of the standard. The minimum installation temperature is shown as a live disagreement rather than resolved to one figure.

What this page does not do is decide a project. It will not tell you that a particular cable satisfies BS 6724 for your installation — that depends on the exact build, the declaration of performance and the accepting authority. Bring us the two specifications and the installation conditions, and we will work the comparison against a construction we actually build.