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BS 6387:2013 category C, W and Z · 0.6/1 kV · CU / MGT / XLPE / LSZH / SWA / LSZH
BS 6387 CWZ Fire Resistant Cable SWA Armoured LSZH
Mica-tape fire barrier cable to BS 6387:2013 with category C, W and Z circuit integrity — 950 °C for 3 hours fire alone, fire with water spray and fire with mechanical shock, each tested separately — in a CU / MGT / XLPE / LSZH / SWA / LSZH construction.
950 °C / 3 h
BS 6387 category C
C · W · Z
Three separate tests
0.6/1 kV
Rated voltage
+90 °C
Max. conductor temperature
↓ Download Datasheet (PDF)
Fire resistance to BS 6387:2013
Categories C, W and Z, tested separately
Mica/glass barrier plus XLPE insulation
Halogen-free, low-smoke LSZH sheath
BS 6387:2013 CWZ · SWA ARMOURED
BS 6387:2013Circuit integrity, categories C, W and Z
950 °C / 3 hCategory C, fire alone
0.6/1 kVRated voltage (Um 1.2 kV)
90 / 250 °CContinuous / short circuit
LSZHHalogen-free, low smoke
Key Specifications
The essentials, at a glance
The five things a specifier checks on a fire resistant cable — and the one category definition that datasheets most often get wrong.
C · W · Z
Three separate BS 6387 tests
950 °C / 3 h
Category C, fire alone
650 °C + water
Category W, 15 + 15 min
950 °C + shock
Category Z, 15 min, shock every 30 s
90 / 250 °C
Continuous / short circuit
6 × D
Bending radius, fixed installation
Product Overview
What CWZ actually means, and why the usual wording is wrong
This is a mica-tape fire resistant cable: a Class 2 stranded annealed copper conductor wrapped in a mica/glass fire barrier tape, XLPE insulated, bedded in a halogen-free compound, galvanised steel wire armoured (SWA) and finished with an LSZH sheath — the construction code CU / MGT / XLPE / LSZH / SWA / LSZH. It is rated 0.6/1 kV and used where a circuit has to keep working while the building around it is on fire.
The CWZ marking is the part that gets misdescribed. BS 6387:2013 is a test method, not a product standard, and it defines three tests: C — resistance to fire alone, 950 °C for 3 hours; W — resistance to fire with water, 15 minutes at 650 °C followed by 15 minutes at 650 °C with a water spray, simulating a sprinkler; and Z — resistance to fire with mechanical shock, 15 minutes at 950 °C with the backing panel struck every 30 seconds. A cable that passes all three is marked CWZ.
The three tests are carried out separately, on separate occasions — not simultaneously. That is the mistake in almost every CWZ datasheet: writing "950 °C for 180 minutes plus water spray plus mechanical shock" as though one cable endured all of it at once. It did not, and a specification written on that basis will not match what the test house actually certifies. The other half of the same mistake is the obsolete category list: A, B, C, S, W, X, Y and Z belong to BS 6387:1994. The 2013 edition retains only C, W and Z, so a page that offers you an "A / B / C temperature grade table" is quoting a superseded edition.
Four related standards get folded into CWZ and should not be. BS 8491 covers circuit integrity for cables of more than 20 mm overall diameter — BS 6387 itself applies to cables of 20 mm or less and rated not more than 600/1000 V. BS EN 50200 is a different small-cable test whose result is a duration class — PH15, PH30, PH60 or PH120 — not a temperature letter. BS 8434-2 tests fire, water and shock at system level for BS 8519 life-safety circuits, and BS 7846 is a cable product standard in which F2 is one flame grade. A cable can carry several of these markings at once; they are not one ladder of "fire ratings".
The mechanism is worth understanding, because it explains the construction. Mica tape wound directly on the conductor sinters into a ceramic shell when the flame reaches it. Even after the XLPE insulation behind it has been destroyed, the ceramic layer keeps the conductors insulated from each other and the circuit alive. That is why the tape sits under the insulation and directly on the conductor rather than around the finished core, and why the tape overlap is the parameter that decides the outcome of the test. The SWA armour then holds the cable together through the mechanical shock element and the collapse of the supporting structure.
More about the manufacturer: About SORIVO →
Key Features
Eight things that decide the specification
BS 6387:2013 Category C
Resistance to fire alone — 950 °C for 3 hours with the circuit energised. This is the longest and hottest of the three tests.
Category W, Fire with Water
15 minutes at 650 °C followed by 15 minutes at 650 °C with a water spray, simulating a sprinkler operating over the cable.
Category Z, Fire with Shock
15 minutes at 950 °C with mechanical shock applied to the backing panel every 30 seconds — the test that models structural collapse.
Mica/Glass Fire Barrier
A mica tape with a glass cloth wound directly on the conductor. In the flame it sinters to a ceramic shell that holds the insulation path after the XLPE has gone.
Steel Wire Armour (SWA)
Galvanised round steel wire armour over a halogen-free bedding, holding the core together through the shock test and protecting the cable mechanically in service.
LSZH Sheath and Bedding
Halogen-free compounds in both the bedding and the outer sheath: HCl emission below 0.5% to BS EN 60754-1, and low smoke density to BS EN 61034-2.
Standard Voltage and Sizes
0.6/1 kV, matching the 600/1000 V ceiling of the BS 6387 test method, in the multicore and single-core ranges below.
Current Edition Only
We quote BS 6387:2013 and its C, W and Z categories. The A, B, S, X and Y letters belong to the 1994 edition and we do not present them as current options.
Applications
Where CWZ fire resistant cable is installed
Circuits that have to keep working during a fire and continue to be safe in the smoke — life-safety and essential services.
01
Fire Pump Feeders
The supply to the fire pump has to survive the fire it is fighting. This is the classic CWZ application, and the cable is usually run in its own protected route.
02
Emergency and Escape Lighting
Final circuit and sub-main supplies to emergency luminaires and exit signage, where the circuit must hold long enough for the building to be evacuated.
03
Smoke Extract and Pressurisation Fans
Supplies to smoke clearance and stairwell pressurisation equipment, which run during the fire and are needed for the longest part of the evacuation.
04
Tunnels and Metro Systems
Tunnel services, ventilation and lighting supplies, where a fire in a confined space and a water main break can occur in the same event.
05
Hospitals and Healthcare
Supplies to life-support, theatre and critical care circuits, where continuity is a patient-safety requirement and evacuation is gradual.
06
Data Centres and Critical Facilities
Fire suppression, control and essential cooling circuits, where downtime has a direct commercial cost and cable is in dense, congested routes.
07
High-Rise and Commercial Buildings
Life-safety and essential services risers, where the cable has to satisfy fire resistance, flame retardance and low smoke in the same specification.
08
Petrochemical and Industrial Plant
Emergency shutdown, alarm and deluge circuits in plants where hydrocarbon fires and firefighting water are both credible events.
Technical Specifications
Full specification sheet
The complete parameter set — the same data our engineers quote from.
Table 1 BS 6387:2013 test categories — each test is carried out separately
| Category | What is tested | Flame temperature | Duration | Water spray | Mechanical shock |
|---|---|---|---|---|---|
| C | Resistance to fire alone | 950 °C ± 40 °C | 3 hours | No | No |
| W | Resistance to fire with water | 650 °C ± 40 °C | 15 min fire + 15 min fire and water | Yes | No |
| Z | Resistance to fire with mechanical shock | 950 °C ± 40 °C | 15 minutes | No | Yes — every 30 seconds |
| CWZ | All three of the above, each tested on a separate occasion | 950 °C (C and Z) and 650 °C (W) | C 3 h · W 15 + 15 min · Z 15 min | Yes, in the W test only | Yes, in the Z test only |
This is a test method, not a product standard: BS 6387:2013 applies to cables of rated voltage not exceeding 600/1000 V and of overall diameter 20 mm or less — for larger cables the corresponding standard is BS 8491. The three tests are conducted separately, not simultaneously: a CWZ cable has passed C, W and Z as three independent tests, and describes it that way. The categories A, B, S, X and Y belong to BS 6387:1994 and are not part of the current edition. Note also that BS EN 50200 is a different test whose result is a duration class (PH15 / PH30 / PH60 / PH120), that BS 8434-2 tests fire, water and shock at system level, and that BS 7846 is a cable product standard with F2 as a flame grade — these are separate markings, not rungs of one scale. Confirmed sizes and the applicable categories are stated on the construction drawing and in the fire test report for the ordered cable; where the required duration or category is larger than the diameter limitation above allows, we will say so before quoting.
Table 2 Construction and performance parameters
| General Information | |
| Product Name | BS 6387 CWZ Fire Resistant Cable SWA Armoured LSZH |
| Construction Code | CU / MGT / XLPE / LSZH / SWA / LSZH — copper conductor, mica/glass fire barrier tape, XLPE insulation, LSZH bedding, steel wire armour, LSZH outer sheath |
| Fire Resistance Standard | BS 6387:2013, Test method for resistance to fire of cables required to maintain circuit integrity under fire conditions — categories C, W and Z |
| Applicable Range of the Test Method | Rated voltage not exceeding 600/1000 V and overall diameter 20 mm or less. For cables above 20 mm overall diameter the corresponding standard is BS 8491 |
| Related Standards (distinct) | BS EN 50200 — a different circuit integrity test, classified PH15 / PH30 / PH60 / PH120. BS 8434-2 — fire, water and shock tested at system level. BS 7846 — a cable product standard, F2 being one flame grade. BS 8491 — circuit integrity for cables over 20 mm |
| Conductor Standard | BS EN 60228 / IEC 60228, Class 2 circular or compacted stranded annealed copper |
| Fire Performance | |
| Category C | Resistance to fire alone: 950 °C ± 40 °C for 3 hours |
| Category W | Resistance to fire with water: 15 minutes at 650 °C ± 40 °C, then 15 minutes at 650 °C with water spray |
| Category Z | Resistance to fire with mechanical shock: 15 minutes at 950 °C ± 40 °C with impact every 30 seconds |
| CWZ | All three tests passed, each carried out separately |
| Flame Propagation | BS EN 60332-1-2 single cable, and BS EN 60332-3-24 bunched cable (Category C) |
| Halogen-Free / Acid Gas | BS EN 60754-1 — HCl content below 0.5%. BS EN 60754-2 — pH not less than 4.3 and conductivity not more than 10 µS/mm |
| Smoke Density | BS EN 61034-2 |
| Circuit Integrity Under Test | The circuit remains energised and must not fail for the duration of each test |
| Electrical | |
| Rated Voltage | 0.6/1 kV |
| Max. Conductor Temperature | +90 °C continuous |
| Short-Circuit Temperature | +250 °C for a duration not exceeding 5 seconds |
| Operating Temperature Range | −5 °C to +90 °C |
| Conductor Resistance (Class 2, 20 °C) | 1.5 mm² = 12.1 Ω/km; 2.5 = 7.41; 4 = 4.61; 6 = 3.08; 10 = 1.83; 16 = 1.15; 25 = 0.727; 35 = 0.524; 50 = 0.387; 70 = 0.268; 95 = 0.193; 120 = 0.153 Ω/km |
| Withstand Test | Routine test on every production length, at the voltage and duration applicable to the selected construction — stated on the test certificate |
| Construction | |
| Conductor | Class 2 circular or compacted circular stranded annealed copper |
| Fire Barrier | Mica tape with a glass cloth, wound directly on the conductor. Sinters to a ceramic shell in the flame |
| Insulation | XLPE (cross-linked polyethylene) over the fire barrier tape |
| Bedding | Extruded halogen-free low-smoke (LSZH) compound |
| Armour | Galvanised round steel wire armour (SWA) |
| Outer Sheath | Halogen-free low-smoke (LSZH) compound, black |
| Core Identification | Colour-coded for small core counts (red, yellow, blue, black and green); numbered white cores for larger counts |
| Installation & Logistics | |
| Bending Radius | ≥ 6 × overall diameter for fixed installation. Confirm against the selected construction where the armour or the core count is larger |
| Current Rating | Depends on the installation method, the ambient temperature and the number of circuits in the group, and is given for the actual route rather than as a single figure |
| Single-Core Range | Available as single-core for power circuits — note that BS 6387 applies to a single insulated conductor only where the cable includes at least one other metallic element, which the armour provides |
| Multi-Core Range | Multi-core constructions for power, alarm and control circuits |
| Packaging | Wooden drum, steel drum or coil per order |
| Standard Lengths | 100 m / 500 m / 1000 m per drum; cut lengths on request |
| MOQ | 500 m — sample orders negotiable |
| Lead Time | 10–20 working days |
The BS 6387 test parameters in Table 1 — the 950 °C and 650 °C temperatures and the 3 h / 15 + 15 min / 15 min durations — are quoted from the published test descriptions of the categories, and the requirement that the three tests are carried out separately is what the standard provides. BS 6387:2013 applies to cables of rated voltage not exceeding 600/1000 V and overall diameter 20 mm or less; for larger cables the corresponding standard is BS 8491, not BS 6387. Conductor resistance values are the Class 2 maxima to IEC / BS EN 60228 at 20 °C. Bending radius and current rating are installation-dependent and are confirmed against the construction drawing for the ordered cable; the current rating is issued for the actual installation method, ambient temperature and grouping rather than as a single number. This page states that the cable is made and type-tested to BS 6387:2013 — it does not claim third-party certification, and no CE certification claim is made; the test report and any third-party certificate applicable to the selected construction are supplied with the quotation.
Certificates & Standards
Verify before you buy — we make it easy
BS 6387:2013 — categories C, W and Z
The test method this cable is type-tested to, quoted in its current edition and with the three categories described as the three separate tests they are. The 1994 category letters A, B, S, X and Y are not presented as current options.
Request fire test report →BS EN 60754 and BS EN 61034 performance
Halogen-free to BS EN 60754-1 with HCl content below 0.5%, acid gas to BS EN 60754-2 with pH not less than 4.3 and conductivity not more than 10 µS/mm, and smoke density to BS EN 61034-2. Flame propagation to BS EN 60332-1-2 and BS EN 60332-3-24.
Request test records →Certification — no claim without the certificate
Third-party approval depends on the exact construction, core count and cross-section, so it is confirmed against the certificate for the cable actually ordered rather than stated as a general claim. The construction drawing and the applicable test report are issued with the quotation.
Request documentation →
Transparency note: certification status and exact scope should always be confirmed against the certificate for the selected product configuration. We provide the certificate and test reports with every quotation — no blank promises.
Quality & Factory
Every length tested before the drum is released
A fire resistant cable is bought for the worst day in the building, so the release checks are recorded per production length rather than per batch.
- 1Incoming material control — conductor, mica/glass fire barrier tape, XLPE compound, armour wire and LSZH compounds are checked against specification before the line starts.
- 2In-line process monitoring — mica tape overlap, insulation thickness, bedding and sheath thickness and the armour wire lay are tracked during production — the tape overlap is the parameter that decides whether the cable survives the fire test.
- 3Electrical routine tests — conductor resistance, insulation resistance and the finished-cable withstand test are measured on every production length and recorded against the drum.
- 4Finished-cable inspection — outer diameter, core identification, armour coverage, sheath surface and the printed marking are checked against the approved construction drawing before the drum is released.
19+
countries served
60+
industrial & panel projects
100%
routine test before shipment
How to Order
From inquiry to loaded carton in 5 steps
Send Inquiry
Tell us the core count and cross-section, the fire category the specification calls for (CWZ or a subset), the voltage and the quantity.
Confirm Configuration
We confirm the construction, the fire category, the conductor size and the armour, and send the quotation within one working day.
Sample Evaluation
Sample for qualification — stocked configurations within a few working days.
Bulk Production
10–20 working days, depending on the core count and cross-section.
Delivery & Support
Drum packing, shipping documents and cut lengths on request, with the construction drawing issued for approval before the first production run.
FAQ
Questions buyers ask before ordering
BS 6387:2013 is a test method for cables that must maintain circuit integrity in a fire. It defines three tests: C — fire alone at 950 °C for 3 hours; W — fire with water, 15 minutes at 650 °C then 15 minutes at 650 °C with a water spray; and Z — fire with mechanical shock, 15 minutes at 950 °C with impact every 30 seconds. CWZ means the cable has passed all three. The important point is that the three tests are carried out separately, not at the same time — a datasheet describing CWZ as "950 °C for 180 minutes plus water plus shock" in one event is describing something the standard does not do. The letters A, B, S, X and Y come from the superseded 1994 edition and are not current categories.
CW means the cable has passed category C (fire alone, 950 °C / 3 h) and category W (fire with water spray, 650 °C, 15 + 15 min). Adding Z adds the mechanical shock test — a further 15 minutes at 950 °C with the cable struck every 30 seconds. Z is the one that models a collapsing structure or falling debris landing on the cable, so CWZ is the appropriate marking where the cable is fixed to a structure that may itself be damaged during the fire. If the project only requires CW, say so: specifying Z when it is not required adds cost without adding protection.
They are different tests, and the results are not interchangeable. BS 6387 gives a temperature letter plus a water and a shock category — C, W and Z — and its categories are the ones with the 950 °C and 3 hour figures. BS EN 50200 applies its own flame and shock condition and reports a duration class: PH15, PH30, PH60 or PH120, in minutes. A cable can be marked to both, and it is common in the UK for a life-safety specification to call for BS 6387 C, W and Z and BS EN 50200 PH120 side by side, with BS 8434-2 for the system-level fire, water and shock test. Tell us which of them the specification actually requires and we quote to that.
Yes — a fire pump supply is one of the standard applications, because the circuit has to keep working while the fire is being fought. Two practical points. First, BS 6387 applies to cables of overall diameter 20 mm or less at up to 600/1000 V, so a large single-core pump feeder may exceed that diameter and falls under BS 8491 instead; the applicable standard is decided by the diameter, not by preference. Second, the fire test covers the cable, not the termination — glands, joints and the support system have to be part of the fire-rated assembly, and the circuit has to be protected against the fire it is feeding into. Tell us the load and the route and we will confirm which standard and which construction applies.
The steel wire armour must be connected to the protective earth at the supply end, and at both ends where the installation is covered by the usual metallic-sheath earthing rules — this is an electrical safety requirement, not a fire performance one, and it is also what lets the armour carry fault current. Use a proper armoured cable gland with an earth tag, and keep the gland and the termination inside the fire-rated assembly. The armour is not a substitute for the circuit protective conductor where the standard requires a separate CPC; in the multi-core construction a green/yellow core can be included in place of relying on the armour.
Because that is what makes the cable survive. The mica/glass tape is wound directly on the conductor, under the XLPE insulation. When the flame reaches it the mica sinters into a ceramic shell. The XLPE insulation behind it will have been destroyed by then, but the ceramic layer keeps the conductors insulated from one another and the circuit live. Putting the tape around the finished core instead would leave the conductor unprotected once the insulation is consumed. This is also why the tape overlap is the critical in-process parameter on this cable — it is tracked during production and checked before the drum is released.
Yes. Both the bedding and the outer sheath are halogen-free low-smoke compounds. To BS EN 60754-1 the HCl content is below 0.5%; to BS EN 60754-2 the pH is not less than 4.3 and the conductivity not more than 10 µS/mm; and smoke density is tested to BS EN 61034-2. Flame propagation is to BS EN 60332-1-2 for a single cable and BS EN 60332-3-24 for bunched cable. Fire resistance, flame retardance and low smoke are three separate requirements, and a life-safety specification usually names all three — this construction answers all three.
MOQ 500 m, with sample orders negotiable. Lead time is 10–20 working days depending on core count and cross-section. Standard delivery is 100 m, 500 m or 1000 m per wooden or steel drum, or in coils, with cut lengths to order. A construction drawing stating core count, cross-section, fire barrier, insulation, armour and outer diameter is issued for approval before the first production run, and conductor resistance, insulation resistance and the routine withstand test result are recorded per production length.
Need CWZ fire resistant cable for a life-safety circuit?
Tell us the cores, cross-section, fire category and quantity — we reply within one working day.
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Send your fire resistant cable requirement
The more detail you give, the faster and more accurate our quotation. Our engineers reply within one working day.
- Core count and cross-section, or the cable schedule reference
- The fire category the specification names — CWZ in full, or a subset such as CW
- Whether BS EN 50200 PH120, BS 8434-2 or BS 7846 F2 is also called for
- Voltage, and whether a separate circuit protective conductor is required
- Whether the installation is a tunnel, a shaft, a riser or a buried duct
- Length per drum or cut lengths, and the quantity for the first order
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