How to Pull Wire Through Conduit

1. Verify conduit fill before anything else

Chapter 9, Table 1 sets the limits: 53% fill for one conductor, 31% for two, and 40% for three or more. For same-size conductors, Annex C gives the answer directly — Table C.1 allows sixteen 12 AWG THHN in 3/4" EMT, for example. For mixed sizes, work it manually with conductor areas from Chapter 9, Table 5 against raceway areas in Table 4. If the run doesn't pass on paper, stop — a jammed pull costs far more than upsizing conduit now.

When pulling exactly three conductors, check the jam ratio: if conduit ID divided by conductor OD lands roughly between 2.8 and 3.2, the conductors can wedge into a triangle at a bend. Change conduit size or configuration to get out of that window.

2. Confirm the bend count — 360° max between pull points

The raceway articles (358.26 for EMT, 344.26 for RMC, 352.26 for PVC) all cap the run at the equivalent of four quarter bends — 360° total — between pull points. That includes offsets and kicks, which crews love to forget: two 30° offsets is 120° of your budget gone.

This isn't bureaucracy — pulling tension multiplies through every bend, and sidewall pressure at the last bend is what strips insulation. If the run exceeds 360°, add a pull point; boxes for 4 AWG and larger have minimum dimensions per 314.28 (straight pulls: eight times the trade size of the largest raceway).

3. Get the pull string in: fish tape or vacuum

For short runs with few bends, a fish tape is fastest — push it through, tie on the string, pull it back. Steel tapes push farther; fiberglass is safer near anything that might be live. Past 100 feet or several bends, tapes bind and buckle.

For long commercial runs, use a conduit vacuum or blower with a foam mouse sized to the conduit. Shoot the mouse with a lightweight line attached, then work up to a rope rated for the job. The mouse also proves the run is clear — if it won't travel, find out why before committing conductors to it.

4. Stage reels and the wire cart so the wire feeds itself

Set reels on jack stands or a wire cart so each spins freely on its own spindle and pays off the top, in line with the conduit entry. Wire should travel as straight as possible from reel to raceway — every hard flip over a box edge adds friction and risks jacket damage.

One person stays at the feed end for the whole pull: keeping conductors parallel and untwisted, applying lube, and calling a stop the second something crosses or birdcages. Feeding is a full-time job.

5. Build a head that won't hang up

For branch-circuit sizes, a staggered head works: strip each conductor a few inches, stagger the attachment points so the bundle tapers instead of forming a lump, loop each conductor through the rope's eye, then tape the head smooth. The finished head should be no fatter than the bundle behind it and slide through a coupling without catching.

For feeders, use a basket grip (Kellems-style) sized to the bundle and taped at the tail, or factory-installed pulling eyes on large parallel runs. Either way, the rope must never pull on insulation — tension goes to the copper or the grip. Respect the manufacturer's maximum pulling tension and sidewall pressure; on calculated pulls those numbers, not the tugger's capacity, set the limit.

6. Lube generously and pull with communication

Use a wire-pulling lubricant compatible with the conductor jacket — never soap or grease, which can degrade insulation. Coat the head and keep applying lube as the conductors feed. Running out mid-run is how conductors get flat-spotted at the last 90.

Feed end and pull end must be able to talk instantly — radios, with agreed calls: pull, stop, slack. A steady, continuous pull beats jerking; once conductors are moving, static friction is broken and tension drops. If tension spikes, stop and find out why before the tugger shaves insulation off somewhere you'll never see until it faults.

7. Protect conductors where they land

Where 4 AWG or larger conductors enter a cabinet, box, or enclosure from a raceway, NEC 300.4(G) requires a fitting with a smoothly rounded insulating surface — in practice, an insulated throat bushing. Install it before the pull, not after, so conductors never drag across a raw metal edge.

At the pull end, don't let conductors kink in the can. Pull enough length for terminations plus dressing, then rack the conductors with gentle bends — a kinked 500 kcmil never lies flat again.

8. Support conductors in vertical runs per 300.19

In vertical raceways, conductor weight can't hang on the terminations — NEC 300.19 requires support at intervals set by Table 300.19(A). For copper: 100 ft for 18 AWG through 1/0, 80 ft for 2/0 through 4/0, 60 ft above 4/0 through 350 kcmil, 50 ft above 350 through 500 kcmil, 40 ft above 500 through 750 kcmil, and 35 ft above 750 kcmil. Aluminum, being lighter, is permitted longer intervals — check the table's aluminum column. One support is required at or near the top of the vertical run.

In the field that means split wedge supports or approved cleats in boxes at those intervals. Plan the support boxes into the layout before the conduit goes up the shaft — you can't add them after the wire is in.

What is the maximum conduit fill allowed by the NEC?

NEC Chapter 9, Table 1 allows 53% fill for one conductor, 31% for two, and 40% for three or more. For same-size conductors, the Annex C tables give the maximum count directly for each raceway type and size.

How many bends can a conduit run have between pull points?

The equivalent of four quarter bends, or 360 degrees total, between pull points. That budget includes offsets, kicks, and saddles, not just full 90s, per the raceway article such as 358.26 for EMT.

Should I use a fish tape or a vacuum to get a pull string in?

Use a fish tape for short runs with few bends. For long runs or multiple bends, blow or vacuum a foam mouse through with a line attached, then use it to pull in the string and rope. The mouse also proves the run is clear.

What kind of lubricant is okay for pulling wire?

Only a wire-pulling lubricant compatible with the conductor insulation, applied to the head and to the conductors as they feed. Never use dish soap, detergent, or grease, which can degrade the jacket.

When do I need a bushing where conductors enter a box?

NEC 300.4(G) requires an insulating fitting with a smoothly rounded surface wherever 4 AWG or larger conductors enter an enclosure from a raceway. In practice that means an insulated throat bushing installed before the pull.

How often do conductors need support in a vertical conduit run?

NEC Table 300.19(A) sets the intervals by conductor size and material. For copper, they run from 100 feet for 18 AWG through 1/0 down to 35 feet for conductors larger than 750 kcmil; aluminum is permitted longer intervals. One support is required at or near the top of the run.