Cable Installation Best Practices

Pulling tension

Maximum pulling tension for copper is commonly taken as 50 N per mm² of conductor cross-section when pulling on the conductors themselves, and considerably less through a sheath grip. Exceeding it stretches conductors, thins insulation and degrades screens invisibly.

Use a dynamometer on any significant pull, lubricate the duct, and add intermediate pulling points on long or heavily bent routes rather than increasing force.

Bend radius

Observe the manufacturer's minimum bend radius both during the pull and in the final dressed position. As a guide, unarmoured LV power cable is typically 6× overall diameter, armoured 8×, and data cable 4× (8× while under tension).

Cable ties pulled tight enough to deform the sheath are a form of bend-radius violation and are a frequent cause of failed data channel tests.

Drums, storage and handling

Always pay off from the top of a rolling drum in the direction marked. Never lay a drum on its side and pull from the coil — that puts a twist into every metre. Keep drums off wet ground, cap the ends against moisture ingress, and store below 40 °C out of direct sunlight.

• Record the pulling tension for the handover file
• Cap and re-seal any part-used drum the same day
• Test after installation, not just after termination
• Photograph containment before ceilings and risers are closed