Floor trunking and floor boxes — cable channels under the floor
Floor trunking and floor boxes — cable channels under the floor
The guide on reference methods for current-carrying capacity covers how the physical installation method of a cable is translated into a reference method (A1 through F) from IEC 60364-5-52. Floor trunking and floor boxes — cable channels installed under, flush with, or on top of the finished floor — are a category for which IEC 61084-2-2 sets additional construction requirements, alongside the general reference-method classification.
What IEC 61084-2-2 adds
IEC 61084-2-2 is a part standard within the IEC 61084 series for cable trunking and ducting systems, specifically aimed at systems installed in or on the floor — often referred to as underfloor (below the finished floor surface), flushfloor (level with the floor surface), or onfloor (on top of the floor, for example in open-plan offices). This standard sets additional requirements on mechanical load-bearing capacity (foot traffic, rolling loads from office chairs or light transport equipment), fire behaviour, and the accessibility of junction/outlet boxes, in addition to the general requirements from the IEC 61084 series for trunking systems.
Why this is a separate category
A cable channel in the floor is exposed to mechanical loads that a wall or ceiling trunking system does not experience: static load from furniture, dynamic load from rolling office furniture, and sometimes point loads from high heels or transport carts. The standard therefore distinguishes load classes, comparable to how wall-mounted trunking is classified by load-bearing capacity, but tailored to floor loading.
Practical relevance
In office renovations where data and power cabling is installed under a raised floor or in floor boxes, the chosen IEC 61084-2-2 load class partly determines which type of channel is suitable for the expected floor loading — a lightweight plastic floor trunking that suffices in an archive room is not automatically suitable under a corridor with regular rolling traffic. In addition, the regular reference-method classification (for example method B or C, depending on the exact configuration) remains relevant for the current-carrying-capacity calculation of the cables themselves.
Common mistakes
- Checking only the reference method for current-carrying capacity and overlooking the mechanical/fire-safety requirements of IEC 61084-2-2 — a floor channel must satisfy both types of requirements.
- Choosing a floor trunking system based on price or availability without weighing the expected floor loading (pedestrians, office chairs, light transport equipment) against the specified load class.
- Making junction boxes in the floor inaccessible by placing fixed floor covering (carpet tiles, laminate) directly over the lid — periodic maintenance and re-cabling require reachable access points.
- Treating floor channels as equivalent to wall trunking when choosing the installation method — the thermal and mechanical conditions under a floor differ from those against a wall, which can affect both the reference method and the load class.
Related
Further reading
- NEN-EN-IEC 61537Cable support systems — cable trays and cable ladders (NEN-EN-IEC 61537)
- NEN-EN 1366-3Fire-resistant cable penetrations — NEN-EN 1366-3
- IEC 61442Cable joints — underground cable connections and repairs (IEC 61442)
- §522.8Underground cables — burial depth and mechanical protection (§522.8)
- §526.3 / IEC 60998Terminal connections compared — spring terminal versus screw terminal, and the accessibility requirement for junction boxes
- IEC 60364-5-52 Bijlage B (Cg)Grouping factor Cg — why bundled cables may carry less than separated cables