Pulling cable through conduit is a fundamental task in electrical installations. Whether you’re wiring a home, commercial space, or industrial facility, it’s essential to do it correctly to avoid damaging the cables. Damaged insulation can lead to short circuits, poor performance, or even fire hazards. The process requires planning, proper tools, and careful execution.
Here’s a step-by-step guide to help you pull cable through conduit safely and effectively.
1. Choose the Right Conduit Size
Start by selecting a conduit that’s large enough for the number and size of cables you need to install. Overcrowding a conduit increases friction, which can damage the insulation during pulling.
Use conduit fill tables (available in the National Electrical Code or online) to determine how many cables of a specific size can be safely installed in a given conduit diameter.
Example: For three 12 AWG wires, a ½” EMT conduit is usually sufficient.
2. Plan the Route Carefully
Before pulling cable, examine the full run of conduit. Take note of:
- Total length
- Number of bends
- Type of bends (90°, 45°, etc.)
- Junction boxes or pull points
If the run includes more than four 90° bends, or exceeds 100 feet without a box, it’s best to break it up with intermediate pull boxes. Too many bends make pulling difficult and increase the risk of damage.
3. Use a Fish Tape or Pull String
To guide the cable through the conduit, you’ll need a fish tape (a flat spring-steel wire tool) or a pull string:
- Insert the fish tape into the conduit from one end and push it through until it exits at the other end.
- Attach the cable(s) to the fish tape using electrical tape, ensuring a smooth, tapered connection.
- If using a pull string (common in new conduit runs), make sure it’s rated for the expected pulling force.
4. Prepare the Cable Ends Properly
Before pulling, strip any sharp edges or burrs from the cable ends and:
- Stagger the cable ends if pulling multiple wires, so they taper gradually.
- Tape the heads tightly and smoothly to avoid snagging.
- Use a pulling grip or mesh sock for longer or heavier pulls.
Smooth taping and secure fastening reduce the chances of the cable catching or tearing insulation inside the conduit.
5. Lubricate if Necessary
For longer runs or conduits with tight bends, use a cable pulling lubricant (also called wire lube or soap). This reduces friction and helps the cable slide smoothly through the conduit.
Apply the lubricant liberally to the cable before and during the pull, especially where resistance is highest.
6. Pull Gently and Steadily
When pulling the cable:
- Work with a partner: one to feed the cable and another to pull.
- Pull slowly, steadily, and avoid jerking or yanking.
- If you feel strong resistance, stop immediately. Forcing the cable can cause insulation damage or stretch the wire.
- Reposition or re-lubricate if needed.
If you’re using a power puller or winch for long runs, ensure the pulling tension stays within cable manufacturer limits.
7. Avoid Twisting and Kinking
Keep the cable straight and untwisted during feeding. Twisting or kinking can damage the internal structure of the wire and make the pull harder.
Use a spool rack or cable reel stand to help unroll the wire smoothly as it’s being fed.
8. Inspect After Pulling
Once the cable is through:
- Check for visible damage to insulation.
- Ensure the cable is not nicked, crushed, or stretched.
- Label the wires as required and secure them properly in boxes or panels.
Conclusion
Pulling cable through conduit without damage requires planning, patience, and the right tools. Always size the conduit appropriately, avoid excessive bends, use smooth and tapered connections, and apply lubricant when necessary. Working methodically and carefully will save time, reduce rework, and ensure a safe and reliable electrical installation.
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