Why the UK has its own codes
UK specifications for fire-resistant cables grew up around British Standards long before CPR classes existed, and they still shape tender documents for offices, hospitals, residential towers and transport buildings. Two standards come up again and again. BS 6387 is a test standard: a cable passes a set of fire tests and is given letters that record which tests it passed. BS 8519 is a code of practice for selecting and installing fire-resistant power and control cables for life safety and firefighting systems: it starts from the system the cable serves and sets categories of performance.
Neither replaces the EU CPR reaction-to-fire class, which in Great Britain is declared on the DoP with CE marking still accepted for construction products following the ministerial statement of September 2024, and UKCA marking optional. A UK fire cable therefore usually carries three separate claims: a CPR class declared on the DoP, a circuit integrity rating per test report, and a flame-retardant result to IEC 60332 per test report.
BS 6387 and the CWZ letters
BS 6387 tests the cable in three separate ways. Each test has its own letter, and the cable is described by the letters of the tests it passed. "CWZ" means it passed all three at the highest level of each.
| Letter | Test | Conditions |
|---|---|---|
| C | Resistance to fire alone | Flame at 950 degrees C for 3 hours |
| W | Resistance to fire with water | Flame at 650 degrees C with water spray, 15 minutes |
| Z | Resistance to fire with mechanical shock | Flame at 950 degrees C with impacts, 15 minutes |
In the fire alone test the letters A, B and C correspond to 650, 750 and 950 degrees C, so "C" is the most severe of the three temperature levels. The W test reflects the effect of sprinklers or firefighting water on a hot cable, and the Z test reflects falling debris. Each letter needs its own sample and its own result on the report. A cable described as CWZ should have a report, or a set of reports, that shows all three passes for that construction.
These test descriptions are taken from consistent secondary sources. For a formal specification, check the conditions against the edition of BS 6387 cited on the report with your test lab.
Partial letters are common and perfectly legitimate when the specification allows them. A cable described as "CW" passed the fire alone and water tests but was not tested, or did not pass, with shock; a cable described only as "C" passed the fire alone test. When comparing offers, check that every supplier quotes the same set of letters for the same construction, because a quote for a C-only cable will often be cheaper than one for CWZ and can look like the better deal until the reports are read side by side.
BS 8519 categories 1, 2 and 3
BS 8519 groups life safety and firefighting circuits by how long they must keep working, and points to the tests a cable must pass for each category. As commonly described:
- Category 1, 30 minutes: EN 50200 PH30 plus the water test of its Annex E.
- Category 2, 60 minutes: EN 50200 PH60 plus a test to BS 8434-2.
- Category 3, 120 minutes: EN 50200 PH120 plus the 120 minute impact and water spray test to BS 8434-2.
The category is chosen by the designer from the system: a fire alarm in a small building may need a lower category than the supply to a firefighting lift or a sprinkler pump in a tall building. The code also covers how cables are supported and installed, because a cable that survives the test but falls off failed supports does not keep the circuit working. The summary above may reflect an earlier edition of BS 8519; confirm the current requirements with the project engineer before writing them into a purchase order.
How the codes relate to IEC 60331
Export projects outside the UK often call for IEC 60331 instead, and many plants hold both kinds of reports. They are not interchangeable. An IEC 60331 report shows circuit integrity under its own flame and shock conditions; a BS 6387 CWZ report shows the three British tests; BS 8519 refers to EN 50200 and BS 8434-2. A cable that holds one report has not automatically passed the others. Our IEC 60331 guide covers the IEC route, and the fire performance classes page shows how the routes sit next to each other.
The construction behind all of them is usually similar: a mica tape fire barrier over the conductor, insulation, fillers and an LSZH sheath, as in our reference 0.6/1 kV Cu/Mica/XLPE/LSZH 4x25 mm2 on the fire-resistant cables page. Smaller fire alarm constructions follow the same idea with fewer cores and smaller conductors; the fire alarm cable guide covers them. Other UK cable types such as BS 6724 LSZH armoured cable and BS 7211 LSZH wiring cable are described in our guide to UK cable types.
Sourcing UK fire cables through the desk
UK buyers often expect an approval from a UK certification body on fire cables. Where a project requires a BASEC approval or another third-party certificate, it belongs to the partner plant for that construction, and the desk checks it in the certifier's public database per order. Only cable carrying the certifier's name under a current approval counts as approved; a report from a laboratory is not the same thing as a certificate.
- Write the requirement per circuit: BS 6387 letters, or BS 8519 category, plus the CPR class and IEC 60332 requirement.
- Match the plant: the desk shortlists partner plants that already hold the reports for the construction and size range.
- Check the documents: report laboratory, date, edition, construction and result; certificate status if one is required.
- Agree a sample or trial drum: custom constructions usually start with a paid sample of 10-50 m.
- Confirm MOQ, lead time and drums in writing: typical wording is on the MOQ and lead time page.
Send the circuit schedule through the quote form with the category for each circuit, and the desk will come back with the matching constructions and the reports that support them.