How To Pull Wire Through Conduit
Pulling wire or cable through conduit is a fundamental skill needed for electricians or anyone who installs wiring systems. Conduits provide protection for electrical wires, shielding them from damage and aiding with maintenance. However, the way in which you pull the wire through the conduit can be a complex process and needs to be done in an efficient and safe manner. Before you start pulling cable, you will want to consider the following: How long is the conduit run that you need to pull the wire through?
Shorter runs are generally easier to pull than longer runs. The longer the run, the more friction will be created as you pull the wire through the conduit. This friction, if high enough, can damage your wires and expose the conductor, which can cause arcs, sparks, or shorts. Additionally, your run length may limit which method can be used. Rods, for example, may not be an option for extremely long runs.
How complex is the conduit path?
Are there any obstacles in the path? How many bends are there and what are the angles of the bends? Obstacles and bends create more friction where the wire rubs against them. With bends, the larger the angle of the bend, the more friction there will be at the inside of the bend. That friction can lead to wire damage or can cause wires to get jammed. Additionally, for complex or long paths, it may be helpful to have a partner to assist you with the pull.
What type of conduit will you be pulling your wires through?
Different types of conduits have different properties that need to be considered. For example, HDPE Conduit is flexible, and could have additional twists or bends that you wouldn't get with straight EMT or PVC conduit. Straight conduit often has sharper bends than a flexible metallic or HDPE conduit. Corrugated conduit will create more friction than smooth conduit and any joints in the conduit (especially with PVC) can cause friction or jam up your wires.
What size is the conduit?
Conductors in your wire will generate heat, and if there isn't enough space in your conduit, you run the risk of exceeding the insulation heat limits, which can lead to that insulation melting and exposing your conductors. The NEC sets standards that must be followed to determine how much space in your conduit can be taken up by your wires. A single conductor can fill 53% or less of a raceway, 2 wires can fill up to 31%, and more than 2 can fill no more than 40%. Refer to our Conduit Wire Fill Charts & Tables page for more information.
How many cables are included in the wire pull?
The more wires you pull at a time, the greater the friction. Jams are typically more common when multiple wires are being pulled. If enough tension is applied, the wires could be damaged or even break, causing conductors to be exposed.
Are there existing wires or cables already in the conduit?
If existing wires will need to stay in place, they must be considered as you determine how much room is left in the raceway for your pull. If the existing wires are no longer needed, you will need to remove them, but may be able to put them to use for your run. (More on that in a bit). Along with the tools described in each of the methods, the following items can make pulling wire through conduit much easier. Once you've considered the above, you can determine what method you will use to pull the cable through the conduit. Below are some of the typical pull methods. This method involves physically pulling the cable through the conduit by hand. Best for: Advantages: Disadvantages: Process: For longer and more challenging runs, a pulling rope or string can be used. The rope is first pulled through the conduit, and then the cable is attached to the rope and pulled back through the conduit. Best for: Advantages: Disadvantages:
Process: A fish tape is a long, flexible, and narrow tool made of steel or fiberglass. The tape is inserted into the conduit, and the cable is then attached to the fish tape and pulled through the conduit by guiding the tape along the desired path. Best for: Advantages: Disadvantages: Process: This specialized tool is designed for pulling cables through conduits and ducts. Conduit rodders are particularly effective for long conduit runs, as they can cover considerable distances without requiring intermediate access points. They are also highly flexible, allowing them to navigate through bends, curves, and obstacles in the conduit easily. Best for: Advantages: Disadvantages: Process: For longer and larger-diameter conduits, a vacuum or compressed air system can be employed. A vacuum system sucks a foam or rubber carrier (called a conduit piston or conduit mouse) through the conduit, carrying the cable along with it. Similarly, compressed air can propel a carrier through the conduit. Best for: Advantages: Disadvantages: Process: A fishing weight, typically made of lead or another heavy material, is attached to the cable, providing additional weight to help guide the cable through the conduit. Best for: Advantages: Disadvantages: Process: Motorized pulling machines apply constant force to pull the cable through the conduit smoothly and efficiently. They are capable of handling heavy loads and can save time and effort compared to manual methods. Best for: Advantages: Disadvantages: Process: Other Articles You May Enjoy:
Conduit Wire Fill Charts & Tables
Formulas for Calculating Conduit & Pipe Bends
Choosing the Right Pipe for Underground Utilities ApplicationsPlanning & Considerations
Additional Cable Pulling Materials
Wire Pulling Methods
Manual Pulling
Pull String/Rope/Tape
Fish Tape
Duct Rodder
Compressed Air / Conduit Mouse
Fishing Weight
Motorized Pulling Machine