Wire Pulling Cheat Sheet

Maximum pulling tension, sidewall pressure, lubricant, and basket-grip / pulling-eye practice from manufacturer installation guides (Southwire cited below). The cable manufacturer’s instructions and the pulling-device rating always control. This is not a full pull calculation (no cumulative tension around a bend series).

⚠ A pull that exceeds tension or sidewall limits can neck down a conductor, ruin insulation, or pull a termination apart inside a raceway you cannot see. Plan the route, the bends, and the set-up before you put a tugger on the rope. Keep people out of the bight of the rope.

1 · Maximum tension on the conductors

Southwire’s pulling-tension sheet and Power Cable Installation Guide use a maximum conductor stress S = 0.008 lb/CM for soft copper and S = 0.006 lb/CM for ¾-hard and AA-8000 aluminum.^[1]^[2]

For n ≤ 3 conductors: T = S × CMIL × n
For n > 3 (Southwire 2405): T = S × CMIL × n × 0.8^[2]
A much smaller EGC pulled with the phase conductors is normally ignored in that calculation.^[2]

Do not exceed the pulling-device rating (eye, bolt, swivel, or grip). Southwire also cautions that other parts of the setup (sheaves, structural supports, sidewall pressure) often limit the pull before the conductor math does, and they mention a 10,000 lb device ceiling in the install guide.^[1]^[2]

Conductor metal Size Number of conductors (phase) being pulled Pulling device Bend radius at the tightest sheave or sweep (ft), optional

Source conflict on the n > 3 factor. Southwire 2405 applies the 0.8 factor when more than three conductors are pulled. Some other industry write-ups use T = S × CMIL × n with no 0.8 factor. This calculator follows Southwire 2405. If the cable maker’s sheet for that job differs, use theirs.

2 · Sidewall pressure

Sidewall pressure is the force that crushes a cable against the inside of a bend. For a single conductor (or a multi-conductor cable under one jacket), Southwire’s basic relationship is SP = T / R, with T the tension coming out of the bend (lb) and R the bend radius in feet. Three single conductors in a cradled or triangular configuration use additional weight-correction formulas in the install guide.^[1]

Recommended maximum sidewall pressure in that guide is typically in the 300–500 lb/ft range depending on cable type; AEIC guidance cited there lists higher values for some constructions. Southwire’s 2405 sheet instead states a maximum sidewall pressure of 1,000 lb (not lb/ft) for 8 AWG and larger and 500 lb for 14–10 AWG — a different document and a different unit presentation.^[1]^[2] Treat this as a conflict: use the cable manufacturer’s number for the cable on the reel. The calculator reports SP in lb/ft from T/R so you can compare it to the 300–500 lb/ft range; it is not an approval to pull.

3 · Basket grips, eyes, and the “knot”

Pulling eye or pulling bolt on the conductors can use the full conductor tension (up to the device rating). This is the preferred high-tension method on large feeders.^[1]
Basket / cable grip over non-leaded cable: Southwire and long-standing trade practice use a conservative 1,000 lb limit on the grip, and you still must not exceed the conductor tension. The install guide notes that under specific conditions the 1,000 lb grip limit can be exceeded — only when the grip manufacturer and the cable manufacturer say so.^[1]
Fit the grip for the cable diameter, seat it fully, and use a swivel so the cable does not spin twist into the raceway. Protect the insulation at the nose of the grip with tape as the manufacturer shows.
A hand pull on small branch-circuit conductors sometimes starts with a properly dressed head (staggered conductors, taped smooth, no bare ends to hang on a coupling). That is not a substitute for a listed grip on a hard pull, and it is not a “knot” in the pulling rope around bare copper — cinching a rope knot onto the insulation can cut it. Use a grip, an eye, or a listed pulling head.

4 · Lubricant and good practice

Use a listed cable pulling lubricant compatible with the insulation (THHN, XHHW, PVC jacket, LSZH, and so on — the lube data sheet names the families). Do not use soap, dish detergent, or oil that can attack the jacket or leave a residue the manufacturer did not approve.
Pre-lube the raceway on long or high-percentage fills, and lube the cables as they enter. More fill and more bends need more lube and a slower pull.
Pull in a continuous motion once you start. Stop and reassess if tension spikes (a jam, a missed bend, or a basket that has peeled).
Leave enough slack for training and for 300.14 conductor length in boxes. Do not use the next pull to yank slack out of a termination you already made.
For fill limits see the THHN fill chart and the conduit fill calculator. High fill is legal at 40% and still a miserable, high-tension pull — plan an intermediate pull box when the math or the route looks ugly.

Sources

Southwire, Power Cable Installation Guide (conductor stress, device limits, sidewall pressure, grips) — https://www.southwire.com/medias/sys_master/installation-manuals/installation-manuals/h29/hb6/8887676141598/PowerCableInstallGuidepdf.pdf
Southwire, Maximum Pulling Tension (2405) — T = S×CMIL×n, 0.8 factor for n>3, aluminum stress, sidewall notes — https://www.southwire.com/medias/2405-Maximum-Pulling-Tension-WEB.pdf?context=bWFzdGVyfHBkZnN8MTA2NDg2MnxhcHBsaWNhdGlvbi9wZGZ8aDhiL2hiNS85MjI1NjYzNTEyNjA2LzI0MDVfTWF4aW11bV9QdWxsaW5nX1RlbnNpb25fV0VCLnBkZnw0NmU3ZDRhNmY4NDliMmRhMzc2MmI4MDNiMzYxYzM1ZTI2MzhkYzUyOTRjOWI5NjNmZDhlNTU3NGUwN2ZlMmY4

Southwire is a trademark of Southwire Company, LLC. Morningstar Electric LLC is not affiliated with or endorsed by Southwire. Polywater and other lubricant brands belong to their owners; use the lubricant the cable manufacturer accepts.

Reference only — not engineering, legal, or code-compliance advice. Results are estimates for qualified persons and must be verified against the NEC edition adopted where the work is done (your selected edition), manufacturer instructions, and the local AHJ. Use is subject to the Terms of Use & Disclaimer. — Morningstar Electric LLC