IEC 60332-3-21:2018

Overview

IEC 60332-3-21:2018 specifies a test method for assessing vertical flame spread of vertically-mounted bunched wires or cables - designated Category A F/R - under defined fire conditions. Intended primarily for type approval testing, this edition clarifies mounting details to improve repeatability and extends applicability to optical fibre cables as well as metallic conductor power cables. The procedure is targeted at special cable designs and is not intended for general use.

Key topics and technical requirements

• Scope: Applies to power cables with conductor cross-sectional area > 35 mm² mounted in a spaced configuration on a standard test ladder, with cables arranged on both front and rear faces.
• Non-metallic volume: Test sample assembled to achieve a nominal total volume of 7 l/m of non-metallic material.
• Flame application time: 40 minutes flame exposure using the ribbon-type propane burner specified in IEC 60332-3-10.
• Test sample: Individual test pieces from the same production length, each at least 3.5 m long; number of pieces chosen to reach 7 l/m non-metallic volume.
• Mounting: Detailed ladder mounting and spacing requirements are defined to improve repeatability and reproducibility of results.
• Measurement: Flame spread is evaluated by measuring the extent of damage (char and burned length) to the bunched cables.
• Annexes:
  • Annex A (normative): Guidance on cable selection for type approval testing.
  • Annex B (informative): Recommended performance requirements.
• Status: Classified as a group safety publication (IEC Guide 104).

Practical applications

• Demonstrating a cable’s ability to limit vertical flame spread in installation-specific configurations where spaced, large cross-section power cables or optical fibre cables are installed on ladders.
• Use cases include verification of special cable constructions required by project specifications for industrial, utility or infrastructure installations where vertical bunching may occur.
• The method supports type approval, product specification, regulatory evidence and safety assessments.

Who should use IEC 60332-3-21

• Cable manufacturers and R&D teams validating fire performance of new cable designs.
• Accredited test laboratories performing standardized vertical flame spread tests.
• Specifiers, safety engineers and procurement teams preparing cable performance requirements.
• Certification bodies evaluating compliance for type approval and product certification.

Related standards

• IEC 60332 series (tests on electric and optical fibre cables under fire conditions)
• IEC 60332-3-10 (apparatus for vertically-mounted bunched cables)
• IEC 60332-3-22 / 3-23 / 3-24 / 3-25 (other category test methods)
• IEC Guide 104 (status as a group safety publication)

Keywords: IEC 60332-3-21, vertical flame spread, Category A F/R, cables under fire conditions, optical fibre cable testing, type approval testing, test ladder, non-metallic volume.