Overview
CLC ISO/IEC/TS 29125:2025 specifies telecommunications cabling requirements to support remote powering of terminal equipment over balanced cabling. The technical specification covers electrical and transmission parameters, installation scenarios, cabling design/configuration (as specified in EN 50173-1), and provides a mathematical model to predict temperature and performance for different bundle sizes, cable constructions and installation conditions. It targets support for SELV (max 60 V DC) and LPS applications (up to 100 W supplied within cabling).
Key scope points:
- Remote power over 4‑pair balanced cabling using currents up to 500 mA per conductor (reference EN 50173 implementations).
- Remote power over 1‑pair balanced cabling using currents up to 2 000 mA per conductor.
- Consideration of how installation (bundling, conduit, ambient temperature) affects current capacity and thermal behaviour.
Key topics and requirements
- Cabling selection and performance: minimum cabling classes and conductor characteristics needed to support remote powering while maintaining transmission performance.
- Installation conditions: ambient temperature, bundle size, proximity to equipment, and conduit vs. suspended-in-air installations - all affect temperature rise and current capacity.
- Thermal modelling: a mathematical model and coefficients to predict temperature rise from power dissipation for various cable types, bundle sizes and configurations.
- Electrical parameters: DC loop resistance limits, DC resistance unbalance (within-pair and pair-to-pair) and guidance to ensure safe and reliable power delivery.
- Connecting hardware: requirements for connectors and patching supporting remote powering.
- Mitigation and testing: recommended mitigation options (separating bundles, using different cabling classes) and detailed test protocols/procedures for measuring temperature rise and verifying installation performance (Annexes A–F).
Practical applications and users
This Technical Specification is practical for:
- Cabling designers and system integrators planning powered networked devices.
- Installers and contractors implementing balanced cabling in buildings, data centres and industrial sites.
- Network engineers and facility managers assessing power delivery capacity and thermal limits of existing cabling bundles.
- OEMs and equipment vendors designing powered terminal equipment that will draw remote power over cabling.
- Safety and compliance teams ensuring SELV/LPS constraints and national regulations are met.
Practical uses:
- Determine allowable current per conductor for a planned installation.
- Model bundle thermal behaviour to avoid overheating and ensure service continuity.
- Select cable classes and installation practices to support up to 100 W LPS or SELV deployments.
Related standards
- EN 50173 series / EN 50173‑1 (cabling design and configuration)
- ISO/IEC 11801‑1, ISO/IEC 14763‑2 (generic cabling and installation)
- ISO/IEC TR 24746 (midspan power insertion)
- Relevant IEC connector standards referenced in the technical specification
Keywords: CLC ISO/IEC/TS 29125:2025, telecommunications cabling, remote powering, balanced cabling, SELV, LPS, cable bundling, temperature rise model, DC loop resistance.