Fire-resistant and fire alarm cable for detection, alarm, emergency lighting, public address and evacuation systems. The grade is chosen by the fire strategy, not by preference — so this page is about how to specify it correctly.
It gets hot. Something falls on it. Then a sprinkler or a hose soaks it while it is still hot. A cable can survive any one of those and fail the moment the other two arrive, which is exactly why the test protocols combine them.
That is what the letters after BS 6387 mean. C is flame alone at 950 °C for three hours. W adds water spray. Z adds mechanical shock at 950 °C. A cable specified as CWZ has passed all three.
The PH number from EN 50200 is simply minutes of survival under flame plus shock — PH30 is thirty minutes, PH120 is two hours.
A cable printed with a standard number has not necessarily been certified to it by a third-party body. Certification by an accredited scheme means the product was tested, the factory is audited, and the certificate can be produced on demand.
On fire cable we quote the certification body and the certificate, not just the standard number. If a cheaper line is marked but not certified, it is offered as exactly that — marked, not certified — so the decision is yours and it is on the paperwork.
In a BS 5839-1 designed system the fire strategy decides which grade applies. Enhanced is not simply "better" — it is required in specific building types, and using standard grade there is a non-compliance.
The highest circuit-integrity classification: 930 °C for 120 minutes under simultaneous flame, mechanical impact and water spray. Specified where evacuation is phased or prolonged — high-rise towers, hospitals, unsprinklered buildings and critical government facilities.
Circuit integrity under flame and mechanical shock for the design evacuation period. The usual choice for fire detection and alarm, emergency lighting, public address and voice evacuation in buildings with a simultaneous evacuation strategy.
Multicore fire-resistant cable with aluminium or polyester tape screen and drain wire, for addressable loops and data-carrying life-safety circuits where the screen is needed against interference as well as fire.
Power-limited fire alarm cable to the North American convention, riser rated — flame height not exceeding 3.66 metres after thirty minutes of vertical burn. Supplied where the design follows NFPA rather than BS.
Every grade above is available in LSZH construction. In an enclosed escape route the smoke and acid gas from burning cable can incapacitate people well before the fire reaches them, which is why LSZH is mandatory in most public buildings.
Where a fire-rated circuit runs through plant rooms, risers or external routes and needs mechanical protection as well as circuit integrity. Available in solid and stranded conductor, screened or unscreened.
Useful when a specification cites one standard and a supplier offers another. These are not interchangeable.
| Standard | What it applies | Duration |
|---|---|---|
BS 6387 C |
Flame at 950 °C, circuit must stay energised | 3 hours |
BS 6387 W |
Flame with water spray applied during the burn | 15 minutes water |
BS 6387 Z |
Flame at 950 °C with repeated mechanical shock | 15 minutes |
EN 50200 |
Flame at 830 °C with mechanical shock every 5 minutes; classified PH15 to PH120 | 15–120 minutes |
EN 50200 Annex E |
As above, with water spray added | Per PH class |
BS 8434-2 |
930 °C with shock and water spray together — the enhanced-grade test | 120 minutes |
IEC 60331-21 |
Flame at 750 °C, circuit integrity maintained | 90 minutes minimum |
UL 1666 |
Vertical riser burn; flame height must not exceed 3.66 m | 30 minutes |
IEC 60754-1/-2 |
Halogen acid gas emitted by the burning sheath | Measured, not timed |
IEC 61034-2 |
Smoke density — light transmittance through smoke in a test chamber | Measured, not timed |
Solid conductors terminate cleanly and hold well in screw terminals, which suits fixed detection loops. Stranded handles repeated flexing and tight containment bends better. Both are supplied in the same grades, so the choice is about installation rather than performance.
Screening matters on addressable loops running near power cable or variable speed drives. An unscreened loop in a noisy riser will work on commissioning day and produce intermittent faults for years afterwards.
| Conductor | Bare copper, solid and stranded |
|---|---|
| Cross-section | 1.0 mm² to 4.0 mm² |
| Cores | 2, 3 and 4 core |
| Screening | Aluminium tape or polyester tape, with drain wire |
| Alarm cable sizes | 14 AWG and 16 AWG, 2-core, screened or unscreened |
| Sheath | Low smoke, zero halogen throughout |
| Variants | Unscreened, screened and armoured — each in solid or stranded |
