Fire resistant cables

Fire resistant cables are used in fire safety, fire detection and fire alarm systems and other applications where specifications require cables with specific performance in the event of a fire.

 

BS 5839-1:2013 Fire detection and fire alarm systems for buildings. Code of practice for system design, installation, commissioning and maintenance

BS 5839-1:2013 includes requirements for fire resistant cables for fire detection and alarm systems. It calls for ‘Standard’ and ‘Enhanced’ fire resistant cables and defines the requirements for these in Clause 26.2. These cables have to comply with EN 60702-1 (with a polymeric sheath), BS 7629-1 or BS 7846.

‘Standard’ fire resisting cables also have to:
a) achieve at least Class PH30 when tested in accordance with EN 50200:2006.
and
b) maintain circuit integrity when exposed to a special flame / mechanical shock / water spray sequence equivalent to achieving a duration of 30 minutes when tested in accordance with EN 50200:2006 Annex E.

‘Enhanced’ fire resisting cables also have to:
a) achieve a 120 minute survival when tested in accordance with EN 50200:2006,
and
b) maintain circuit integrity when exposed to a special flame / mechanical shock / water spray sequence equivalent to achieving a duration of 120 minutes when tested in accordance with BS 8434-2:2003+A2:2009.

Only cables complying with these requirements are listed as ‘Standard’ or ‘Enhanced’ under BS 5839-1, Clause 26.2.

BS 8519:2010 Selection and installation of fire-resistant power and control cable systems for life safety and fire-fighting applications - Code of practice

BS 8519:2010 gives guidance and recommendations on the selection and installation of power and control cable systems which are required to maintain their circuit integrity for life safety and fire-fighting applications. It also gives specific recommendations for electrical system design for such applications, and recommended limits for survival times.

Category 1: means of escape (30 min fire survival time).
• power cables of 20 mm overall diameter and above meeting the 30 min survival time when tested in accordance with BS 8491, or
• control cables meeting the PH30 classification when tested in accordance with EN 50200:2006, and the 30 min survival time when tested in accordance with Annex E of that standard

Category 2: means of escape (60 min fire survival time).
• power cables of 20 mm overall diameter and above meeting the 60 min survival time when tested in accordance with BS 8491 or
• control cables meeting the PH60 classification when tested in accordance with EN 50200:2006, and the 120 min survival time when tested in accordance with BS 8434-2:2003+A2:2009

Category 3: fire-fighting (120 min fire survival time).
• power cables of 20 mm overall diameter and above meeting the 120 min survival time when tested in accordance with BS 8491, or
• control cables meeting the PH120 classification when tested in accordance with EN 50200:2006, and the 120 min survival time when tested in accordance with BS 8519 Annex B.

Building Regulations 2010 - Fire Safety - Approved Document B
The Building Regulations 2010 - Fire Safety - Approved Document B - Volume 2 - Buildings other than dwelling houses defines a protected power circuit to be able to continue to function during a fire. A protected circuit for operation of equipment in the event of fire should consist of a cable meeting at least the requirements of PH30 when tested in accordance with EN 50200. Larger or complex buildings may require fire protection systems to operate for extended periods during fire and guidance on such systems is given in BS 5839-1, BS 5266-1 and BS 8491 (BS 7346-6).

Other Standards Used
The other standards and test methods currently used for certification are listed below. This list includes some "withdrawn" standards. Where possible, these will be replaced by the superseding standards when certificates are renewed. However, where withdrawn standards are called up by current standards, certification to the withdrawn standard may need to be maintained until the calling standard is amended to remove the reference:

- BS 6387:1994 Performance requirements for cables required to maintain circuit integrity under fire conditions
- BS 7629-1:1997 Thermosetting insulated cables with limited circuit integrity when affected by fire. Part 1: Multicore cables
- BS 7629-1:1997 (Incorporating Amendment Nos.1 and 2) Thermosetting insulated cables with limited circuit integrity when affected by fire. Part 1: Multicore cables (The provisions introduced by amendment No.1: 2004 are effective from 1st April 2004)
- BS 7629-1:2008 Electric cables - Specification for 300/500 V fire resistant screened cables having low emission of smoke and corrosive gases when affected by fire - Part 1: Multicore and multipair cables
- BS 7846:2000 Electric cables 600/1000V armoured fire-resistant cables having thermosetting insulation and low emission of smoke and corrosive gases when affected by fire
- BS 7846:2009 Electric cables - Thermosetting insulated, armoured, fire - resistant cables of rated voltage 600/1 000 V, having low emission of smoke and corrosive gases when affected by fire - Specification
- BS 8434-2:2003+A2:2009 Method of test for assessment of the fire integrity of electric cables - Part 2: test for unprotected small cables for use in emergency circuits- EN 50200 with a 930°C flame and with water spray
- BS 8491:2008 Method for assessment of fire integrity of large diameter power cables for use as components for smoke and heat control systems and other certain active fire safety systems
- BS 8519:2010 Selection and installation of fire-resistant power and control cable systems for life safety and fire-fighting applications - Code of practice
- EN 50200:2006 Method of test for resistance to fire of unprotected small cables for use in emergency circuits
- EN 50267-2-1:1999 Common test method for cables under fire conditions- tests on gases evolved during combustion of materials from cables - procedures - Determination of the amount of halogen acid gas
- EN 50267-2-3:1999 Common test methods for cables under fire conditions - Tests on gases evolved during combustion of materials from cables - Procedure 2-3: Procedures - Determination of degree of acidity of gases for cables by determination of the weighted average of pH and conductivity
- EN 60332-3:2009 Tests on electric and optical fibre cables under fire conditions - Part 3: Test for vertical flame spread of vertically mounted bunched wires or cables
- EN 60702-1:2002 Mineral insulated cables and their terminations with rated voltage not exceeding 750V - Part 1: Cables
- EN 61034-2:2005 Measurement of smoke density of cables burning under defined conditions - Part 2: Test procedure and requirements (IEC 61034-2)
- EN 61034-2: 2005 Measurement of smoke density of cables burning under defined conditions
- IEC 60331-1:2009 - Tests for electric cables under fire conditions - Circuit integrity - Part 1: Test method for fire with shock at a temperature of at least 830°C for cables of rated voltage up to and including 0,6/1,0kV and with an overall diameter exceeding 20mm.
- IEC 60331-2:2009 - Tests for electric cables under fire conditions - Circuit integrity - Part 2: Test method for fire with shock at a temperature of at least 830°C for cables of rated voltage up to and including 0,6/1,0kV and with an overall diameter not exceeding 20mm.
- IEC 60331-21:1999 Tests for electric cables under fire conditions - Circuit integrity - Part 21 Procedure and requirements - Cables of rated voltage up to and including 0,6/1,0kV
- IEC 60332-3:2009 Tests on electric cables under fire conditions - Part 3: Tests on bunched wires or cables
- IEC 60754-1:2011 Tests on gases evolved during combustion of materials from cables - Part 1: Determination of the amount of halogen acid gas
- IEC 60754-2:2011 Tests on gases evolved during combustion of materials from cables - Part 2: Determination of acidity (by pH measurement) and conductivity
- IEC 61034-2:2005 Measurement of smoke density of cables burning under defined conditions

Notes:
1) The rated voltages Uo/U recognised for BS 6387:1994 are, 300/500V and 450/750V, and for BS 7629-1 are 300/500V, where Uo is the power-frequency voltage to earth and U is the power-frequency voltage between conductors.
2) Testing of single core cable to BS 6387:1994 is not recognised by the standard. This is because it requires the cable to have at least two metallic elements. Therefore LPCB approval of single core cable is based on the cable being tested in a stainless steel conduit.
3) All BS 6387 approvals must include EN 50267-2-1 (acid gas) and EN 61034-2 (smoke density) testing
4) MICC Cables approved to BS 5839-1:2002+A2:2008 Clause 26.2 must be sheathed with an overall polymeric covering.
5) EN 50200:2006 Annex E and BS 8434-2:2003+A2:2009 provide methods of test that meet the requirements for a special flame / mechanical shock / water spray sequences described in BS 5839-1:2013, Clause 26.2 d) and e), respectively.
6) BS 8491 does not cover cables with a voltage rating that exceeds 600/1000V or where the external cable diameter is less than 20mm.
7) BS 8519 standard covers both Power and Control cables; different test methods apply to each cable type. Control cables up to & including 4.0mm2 can be approved to BS 8519.

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