Pull Tension
Excess tension stretches the conductors and changes the pair geometry the cable was built with. The damage is invisible and permanent, and it shows up as a return loss failure at certification.
Use a pulling eye or a proper grip rather than wrapping the cable round a hand, and pull steadily rather than in jerks. If a run needs more force than one person can comfortably apply, change the route or add a mid-point.
Bend Radius
A tight bend deforms the pairs against each other and changes impedance at that point. The usual guidance is a minimum bend radius of four times the cable diameter for unshielded cable and eight times for shielded.
The place this is most often violated is the last 300 mm at the patch panel, where the installer is trying to dress a full bundle into a tight space.
Untwist Length At The Termination
The twist is what rejects noise. Every millimetre of untwisted conductor at a termination is a millimetre of unprotected cable, and on CAT6 the tolerance is around 13 mm.
This is the single most common cause of a field-terminated link that fails certification while a factory-terminated cord on the same run passes.
Separation From Power
- Maintain the separation distance your local installation standard specifies
- Cross power cable at right angles rather than running parallel
- Where a long parallel run is unavoidable, use screened cable and bond it
- Keep data cable out of the same compartment as unscreened power in trunking
Before You Close The Ceiling
- Certify every link, not a sample
- Record drum numbers against link IDs for future traceability
- Label both ends before the cable leaves the ladder
- Photograph the containment route before it is boarded over
Applying this to a live project? Send the specification and we will tell you how it lands for your case — ethernet cable installation — avoiding the common failures is exactly the kind of question we answer whether or not there is an order attached.
