IEC 61156-1-4:2018

Overview - IEC 61156-1-4:2018 (conductor heating in bundled cables)

IEC 61156-1-4:2018 provides a method to assess conductor heating in bundled multicore and symmetrical pair/quad cables used for digital communications when remote powering (e.g., PoE/PoEP) is deployed. It specifies how to measure temperature rise on cable sheaths in reference environmental conditions and defined test arrangements (free air, cable tray, conduit, sealed conduit). The document is guidance for thermal assessment of cable bundles - not a prescriptive test method - and replaces IEC PAS 61156-1-4 (2010) with revised mathematical modelling and multiple test arrangements.

Key topics and technical requirements

• Purpose: determine temperature rise of cable bundles under specified remote powering currents to evaluate expected performance and insulation suitability.
• Test arrangements covered: free air, cable tray (open tray), conduit, and sealed conduit.
• Bundle geometry: uses dense hexagonal packing for repeatable heat dissipation; example bundle sizes include 1, 7, 19, 37, 61, 91 cables.
• Measurement approach:
  • Thermocouples placed on the outer sheath at the centre of the bundle and at defined positions to capture temperature distribution.
  • Recommended bundle length ≈ 4 m; centre cable length 70–80% of surrounding layer lengths to reduce end effects.
  • Current applied in a balanced configuration with conductors connected in series so the same current flows through the setup.
  • Assessment includes concatenated loop resistance, ambient conditions, and expression of steady-state temperature rise.
• Modelling: Annex A provides a cable heating model and data-evaluation guidance; the standard revised the mathematical approach from the PAS edition.

Practical applications

• Assessing the thermal impact of remote powering (PoE / PoEP) on multicore four‑pair data cables.
• Predicting current carrying capacity (ampacity) of data cables in bundled installations and avoiding insulation degradation or safety hazards.
• Informing installation decisions for cable trays, conduits, and sealed ducts where bundled cables may overheat.
• Supporting product specifications, performance risk assessments, and comparative laboratory evaluations of cable designs.

Who should use this standard

• Cable manufacturers and R&D teams evaluating cable construction and thermal behavior.
• Test laboratories and compliance engineers doing thermal assessments of data cabling under remote powering.
• System integrators, installers and specifiers who design cable routes and containment for PoE deployments.
• Standards bodies and technical committees aligning installation guidance and safety limits.

Related standards

• IEC 61156-1 (Multicore and symmetrical pair/quad cables - Generic specification) and other parts of the IEC 61156 series.
  For authoritative copies and the latest edition, consult the IEC webstore.