7.1 Cable Pulling Setup, Pull String, and Tension Control

Fundamentals of Pull Setup

Cable pulling setup is everything that happens before tension is applied to the conductor. A BICSI Installer 2 Copper technician who rushes setup risks exceeding the 25 lbf (110 N) maximum pulling tension on 4-pair cable, damaging the jacket at conduit throats, or snapping a pull line mid-run. Setup includes inspecting the pathway, positioning personnel, selecting pulling hardware, and establishing how the team will communicate during the pull.

Pre-Pull Pathway Inspection

Walk the entire pull route before rigging. Confirm:

• Conduit ends have bushings or bell mouths—sharp EMT edges cut jackets under tension
• Pull boxes are accessible and covers are removed
• Total degrees of bend between pull points do not exceed 270 degrees (NEC and BICSI best practice); ideally keep bends to 180 degrees or less for long horizontal runs
• Conduit fill from existing cables leaves room for the new pull (maximum 40% cross-sectional fill for three or more conductors per NEC)
• No water, sharp debris, or abandoned wire obstructs the duct

For empty conduit, verify a mandrel test (passing a rubber or foam test plug sized to ~90% of conduit diameter) was completed during construction. A failed mandrel test means the installer discovers a crushed duct or misplaced joint only after the cable is halfway through.

Pull String and Mule Tape Installation

Empty conduit must contain a pull string or mule tape (also called pull tape or fish tape when used in shorter sections) before the cable is attached. Install the line using one of these methods:

Mule tape is preferred for commercial copper pulls because it is flat, low-friction, and printed with sequential footage marks. Select tape rated for the anticipated pull tension—typically 1,100 lbf (5 kN) or greater for backbone pulls. Never use undersized mason's line or utility twine; breakage inside a filled conduit is expensive to recover from.

Attach the cable to the pull line with a swivel between the grip and the tape. The swivel prevents twist from transferring into the cable pairs as the grip rotates through bends. Use a mesh pulling grip sized to the cable OD for backbone pulls; for 4-pair horizontal cable, a non-conductive pulling sock or taped breakout method that grips the jacket evenly is standard.

Leaving Pull String for Future Use

BICSI best practice: after the cable pull, leave a new pull string in the conduit for future additions. Tie the replacement string to the end of the cable before pulling so it trails through behind the cable. This costs nothing during the initial pull and saves a complete re-stringing operation later.

Lubrication

Cable-pulling lubricant reduces sidewall friction where cable slides against conduit walls, especially on long runs, multiple 90-degree bends, or vertical risers. Apply lubricant generously to the cable jacket as it enters the conduit and at each pull-box entry.

Lubricant selection rules:

• Use lubricant compatible with the cable jacket (PVC, FEP, LSZH)—verify with the cable manufacturer
• Water-based polymer lubricants are common and clean up easily
• Never use petroleum-based grease on plenum or low-smoke cables—it can chemically attack the jacket
• Apply continuously during the pull at box openings, not only at the start

Lubricant can lower pulling tension by 30–50% on difficult runs. Even with lubricant, monitor tension—lubricant does not override the 25 lbf limit on 4-pair cable.

Bend Limits and Tension Control

Bend Accumulation Between Pull Points

The NEC limits conduit bends to 360 degrees total between pull points (some jurisdictions allow 270 degrees per BICSI/TDMM guidance for communications pulls). Excessive bends increase friction exponentially. If a route requires more bends than permitted, install an additional pull box or conduit body to break the pull into segments.

At each bend, pulling tension spikes on the cable's outer wall. This is where jacket thinning and pair deformation occur. Slow the pull through bends and ensure personnel on the feed end are not pushing cable into the conduit—pushing compounds tension at snag points.

Maximum Pulling Tension

Measure tension with an inline dynamometer (tension meter) on critical pulls. If no meter is available, communicate constantly— the pulling end should feel steady resistance, never jerking. Stop immediately if the cable binds.

Figure-8 for Large Cables

When pulling large-diameter backbone cables or long horizontal runs from a stationary reel, use the figure-8 technique instead of pulling directly off the reel through a 90-degree bend at the reel hub. The figure-8 method:

1. Position the reel so cable pays off the top
2. Run cable back and forth on the floor in a figure-8 pattern (typically 10–15 feet per loop)
3. Pull from the crossover point of the figure-8 into the conduit

This eliminates the sharp bend at the reel flange, which is a common source of jacket damage and pair deformation on Category-rated and multi-pair cables. For 4-pair horizontal pulls from a box reel, use a reel jack or axle stand so the reel spins freely—never pull cable off a reel lying flat on its side.

Communication Between Pullers

Copper pulls require at least two people on runs longer than a single room: one at the pulling end (tension side) and one at the feeding end (payout side). On long or riser pulls, station an intermediate person at each pull box.

Establish signals before starting:

• "Pull" — apply steady tension
• "Stop" — freeze immediately
• "Ease" — reduce tension; cable is binding
• "Feed" — payout more cable from the reel

Use two-way radios on large sites where line-of-sight is impossible. The feeding end controls how fast cable enters the conduit; the pulling end controls tension. If communication fails, stop the pull.

Protecting Cable Ends

The cable end is the most vulnerable point during a pull. Protect it by:

• Installing a pulling eye or taped cone over the end to prevent pairs from catching on conduit joints
• Leaving the end sealed with the factory cap until termination—if the cap is removed for grip attachment, re-tape immediately
• Never letting the bare end drag on the floor or through dirty pull boxes
• Keeping the end above standing water in underground pulls

If pairs become exposed or untwisted during grip attachment, cut back to a clean section before termination. A damaged end cannot be terminated to Category 6A standards.

Reel Handling

Proper reel handling prevents twists and sidewall compression:

• Mount the reel on a shaft with a brake to prevent overrun
• Pull from the top of the reel in the direction of the payout (check manufacturer arrow if marked)
• Never drop reels—impact can deform the cable stack inside
• Store reels indoors; UV and moisture degrade jacket material before installation
• Rotate stock—use oldest reels first

For box-pack cable, pull from the center core without kinking the inner wraps. If the cable locks up inside the box, do not yank—open the box and re-stage the cable.

Setup Summary

A disciplined pull setup—inspected pathway, rated pull line, swivel and grip, compatible lubricant, tension monitoring, figure-8 payout for large cable, protected ends, and clear team communication—delivers copper cable that certifies on the first test. Skipping any of these steps invites hidden damage that no amount of termination skill can fix.