Trunking sized too small for the cable bundle it’s meant to carry is a common and avoidable installation problem — cables end up jammed in, the lid won’t close properly, and future cable additions become impossible. Sizing trunking correctly from the start avoids a costly re-run.
What trunking size does a typical run need?
Mini trunking (16x16mm to 40x40mm) suits single or light domestic cable runs; midi and maxi sizes handle multiple office circuits; heavy-duty industrial trunking is needed for bundled multi-core factory cable runs.
- Mini trunking — 1-2 cables, domestic and light residential use
- Midi/maxi trunking — multiple office circuits, light commercial installations
- Heavy-duty/industrial trunking — bundled cable runs, factory floors, plant rooms
How much spare capacity should be built into a trunking size?
As a working rule, trunking should be sized to run no more than roughly 45% full at installation, leaving room for future cable additions without needing a full trunking replacement.
This is the same principle as leaving spare ways on a distribution board — undersizing to save a small amount on the initial order almost always costs more later when additional circuits need to be added.
Frequently Asked Questions
Should power and data cables share the same trunking compartment?
No — trunking carrying both should have segregated compartments, which is standard on midi and maxi sizes, to comply with wiring regulations separating power and data cabling.
Does Fembosco supply trunking fittings, not just straight lengths?
Yes — internal and external angle pieces, tees, couplers, and end caps are stocked alongside straight lengths so an installation isn’t held up waiting on fittings separately.
Conclusion
Size trunking for the cable bundle plus spare capacity, not just what’s needed on day one — and keep power and data segregated in separate compartments on any run carrying both.