BBTRZ-0.6/1kV
BBTRZ Flexible Mica Insulated Fire Resistant Cable
Fire performance that clears BS 6387 C, W and Z without the handling penalty of a rigid copper tube.
Being precise about terminology helps specifiers: BBTRZ carries no magnesium oxide and no metal tube, so it is not mineral insulated in the BTTZ sense. Its barrier is a synthetic phlogopite mica and glass-fibre composite wrapped over a flexible Class 5 conductor, backed by a ceramic-forming compound and a halogen-free sheath. What decides the purchase is the test outcome, and this construction passes BS 6387 category C at 950 °C, W with water spray and Z with mechanical shock.
Because there is no tube to draw, BBTRZ is produced in continuous lengths and handled like a flexible power cable: it bends to 6 × OD, pulls through long conduit runs and can be re-routed during commissioning without work-hardening a sheath. Voltcore builds it at 0.6/1 kV from 1.5 mm² to 300 mm² in one to five cores, with 6/10 kV and 8.7/15 kV versions where a medium-voltage feeder also has to survive a fire.
Specification
| Item | Value |
|---|---|
| Rated voltage U0/U | 0.6/1 kV (6/10 kV and 8.7/15 kV on request) |
| Conductor | Flexible plain copper, Class 5, IEC 60228 |
| Fire barrier | Two layers synthetic phlogopite mica tape on glass-fibre cloth, minimum 30% overlap |
| Insulation | Ceramifiable cross-linked polyolefin, 90 °C continuous |
| Filler and binder | Glass-fibre and magnesium hydroxide mineral fill, closed with a glass-fibre tape |
| Sheath | LSZH thermoplastic polyolefin, black or orange, UV stabilised |
| Circuit integrity | BS 6387 C (950 °C, 180 min), W (650 °C plus water), Z (950 °C plus shock); BS 8491 |
| Conductor temperature | 90 °C continuous, 250 °C short-circuit for up to 5 s |
| Min bending radius | 6 × OD during installation |
| Cross-section range | 1.5 – 300 mm² multi-core; 1.5 – 630 mm² single-core |
| Smoke and acidity | IEC 61034-2 ≥ 60% transmittance; IEC 60754-1 ≤ 5 mg/g; IEC 60754-2 pH ≥ 4.3 |
Layer-by-layer construction
Listed from the conductor outward. Read this alongside the specification table — the two together tell you whether the cable will survive its installation method.
- 1. ConductorClass 5 flexible stranded plain copper, IEC 60228
- 2. Fire barrierTwo layers synthetic phlogopite mica tape on glass-fibre cloth backing, minimum 30% overlap
- 3. InsulationCeramifiable cross-linked polyolefin, colour-coded, 90 °C rating
- 4. Mineral fill and binderGlass-fibre and magnesium hydroxide fill over the laid-up cores, closed with a glass-fibre tape
- 5. Outer sheathLSZH thermoplastic polyolefin, black or orange, UV stabilised
Reference dimensions and weights
| Nominal cross-section (mm²) | Conductor structure (n × mm) | Insulation thickness (mm) | Approx. overall diameter (mm) | Approx. weight (kg/km) | Max. DC resistance at 20 °C (Ω/km) |
|---|---|---|---|---|---|
| 5 × 4 | 56 / 0.30 | 0.7 | 16.6 | 430 | 4.95 |
| 5 × 6 | 84 / 0.30 | 0.7 | 18.0 | 555 | 3.30 |
| 5 × 10 | 84 / 0.40 | 0.7 | 21.4 | 850 | 1.91 |
| 5 × 16 | 126 / 0.40 | 0.7 | 24.6 | 1250 | 1.21 |
| 5 × 25 | 196 / 0.40 | 0.9 | 29.4 | 1900 | 0.780 |
| 5 × 35 | 276 / 0.40 | 0.9 | 32.8 | 2520 | 0.554 |
| 5 × 50 | 396 / 0.40 | 1.0 | 37.8 | 3420 | 0.386 |
| 5 × 70 | 360 / 0.50 | 1.1 | 42.6 | 4620 | 0.272 |
Reference figures for preliminary sizing and drum planning. Overall diameter and weight vary with strand construction and sheath thickness tolerance; certified drawings are issued with each quotation.
Engineering characteristics
- Passes BS 6387 C at 950 °C for 180 minutes, W with water spray and Z with mechanical shock despite having no metal tube.
- Class 5 conductor and 6 × OD bending radius let a single length run from board to load through conduit a rigid MI cable could not enter.
- Ceramifiable insulation compound converts to a hard ceramic at flame temperature, holding conductor spacing after the polymer has gone.
- Halogen-free sheath measured to IEC 60754-1 at not more than 5 mg/g acid gas, IEC 60754-2 pH not below 4.3, IEC 61034-2 transmittance not below 60%.
- No copper tube means no pot seals, no moisture-sensitive powder and no dedicated terminating tools.
- 90 °C continuous and 250 °C short-circuit ratings for 5 s, so ampacity follows standard XLPE tables.
- Supplied in long drum lengths, 500 m and above in smaller sizes, which removes joints from a vertical riser.
Typical applications
- Fire pump, smoke control and evacuation lift circuits in towers with congested pulling routes
- Emergency lighting and fire alarm risers in hospitals, airports and metro stations
- Retrofit of fire circuits in existing buildings where conduit cannot accept rigid MI cable
- Tunnel and underground station services needing survival of fire plus water spray
- Data centre and telecom essential-power feeders
- Industrial emergency shutdown and deluge valve circuits
Ordering options
- WDZAN-BBTRZ — halogen-free flame-retardant class A sheath for tunnel and metro specifications
- Copper-braid screened version for variable-speed drives feeding fire pump motors
- 6/10 kV and 8.7/15 kV constructions with conductor and insulation screens
- Orange or red sheath printed FIRE ALARM or EMERGENCY to match identification schedules
- Pre-terminated sets with lugs, glands and heat-shrink cut to floor-by-floor lengths
Standards manufactured to
- BS 6387 (C/W/Z)
- BS 8491
- GB/T 19216.21
- IEC 60331-21
- IEC 60502-1
- IEC 60754-1
- IEC 60754-2
- IEC 61034-2
- IEC 60332-3-24
Manufactured to other standards on request. Send the standard number with your RFQ and we will quote against it rather than against a near-equivalent.
Price and availability for BBTRZ Flexible Mineral Insulated Fire Resistant Cable
Include cross-section, core count, voltage grade, route length and installation method — those five determine price more than anything else on the page.
- Engineer-reviewed before pricing
- Reference drawings issued with the quotation
- Free sample up to free sample up to 5 m
BBTRZ Flexible Mineral Insulated Fire Resistant Cable — frequently asked questions
If BBTRZ has no magnesium oxide, why is it called mineral insulated?
The name is a market convention rather than a construction statement. BBTRZ uses mica and glass-fibre mineral tapes with a magnesium hydroxide fill — inorganic materials, but not the compressed MgO powder of true MI cable. It reaches the same BS 6387 categories, so it substitutes where a specification is performance-based, not where the drawing explicitly names MgO insulation.
Does BBTRZ need the same termination kit as BTTZ?
No. BBTRZ terminates with standard compression lugs, cable glands and heat-shrink: there is no pot seal, no hygroscopic powder and no brass gland kit. Gland bores follow normal flexible-cable sizes, so an installation crew needs no tooling beyond what it already carries for XLPE cable, and a damaged end does not spoil the whole length.
Can BBTRZ be installed outdoors or buried directly?
The standard LSZH sheath is UV stabilised and handles outdoor exposure on trays and in ducts, but direct burial needs mechanical protection. Voltcore supplies a steel-tape-armoured variant for that duty. For permanently wet locations specify the armoured version with sealed glands, because while the fill is not hygroscopic, standing water inside a termination is still a fault risk.
Which test certificate should I ask a supplier for?
Ask for the full BS 6387 report naming the categories achieved — C at 950 °C for 180 minutes, W with water spray, Z with shock — plus BS 8491 for tunnel work. Voltcore issues the report with the quotation together with the sample size tested, because some approvals accept only the cross-sections actually tested and not an extrapolation across the range.