No two electrical installations are alike, especially when pulling cable through conduit is involved. Architects often require electricians to place conduit in difficult places and cramped work areas using various electrical tools. Conduit access points frequently vary from ceiling height to just above the floor or even below grade. And then there are jobsite conditions like temperature, moisture and humidity or even a cable’s insulation texture that can cause pulling tension to change significantly sometimes during the same shift.
Uncontrolled jobsite factors that affect productivity can also become safety concerns. Contractors typically think of the physical work involved with pulling even small wire as minimal. But OSHA experts disagree. Their safety specialists regard pulling electrical cable as a serious health exposure for electricians.
When cable pulling is performed manually, electricians are often forced to give that extra hard tug, assume awkward postures, and perform repetitive motions to move past an obstruction. Then there’s the reaching, bending, and climbing electricians endure to position pulling ropes and cables. These tasks expose them to muscle strains and even long-term muscular illness.
Contractors need an electrical tool that makes cable pulling a safe and efficient operation in all conditions. The right pulling tools can minimize the risk of insulation damage and increase productivity. The old saying sums it up perfectly. Damaged insulation is the same as no insulation.
But recently, equipment manufacturers have made great strides in semi-automating cable pulling while making the puller’s duties more ergonomically friendly. Contractors can now choose pulling equipment that does an excellent job faster, easier and safer – and that adds up to a project where call backs are less likely. And it’s a trend that OSHA recommends. Using the current generation of mechanical wire puller reduces the risk of jobsite injuries and prevents cumulative trauma disorders.
Knowing Your Cable Tension
The key to an efficient pulling operation is properly matching the equipment needed to the proper pulling tension. Too much pulling pressure can cause risk to the insulation and to the conduit, while too little may stretch the wire.
“It’s a matter of getting it right” says Brian Kester, Director of Training for Greenlee.
Fortunately, the National Electrical Code offers contractors guidance on how to calculate the potential pulling tension. Kester’s associates at Greenlee have simplified the NEC data with its PF8 Cable Puller Estimator. The Excel-based calculator, which works with Windows 7, Vista, X P and Mac, provides electricians an approximation of the pull force required to install electrical cordage into a conduit. It’s an approximation because of jobsite variables including the amount of lubrication, the cable’s surface texture and even the cable’s lay not being uniform along the length of a conduit run.
Contractors enter data from each leg of the run including length of run, elevation change and degree of each bend. The final input is the weight of the cable and an estimation of the coefficient of friction. Contractors can download the program for free at https://www.greenlee.com/software/PF8download.html
Matching Puller To Tension
A puller manufacturer like Greenlee offers contractors a range of pullers and related products that can be matched to each conduit pulling application. When pulling tension is in the less than 1000 pressure range (which is common in residential and light commercial applications) the electrical tool of choice is the G3 TUGGER™ Cable Puller.
The Greenlee UT10-22 is a good match for larger projects requiring heavier cable and greater pulling tensions. This recently released semiautomatic unit is the only two-speed puller on the market right now. Operators can shift from high speed/low load pulling to low speed/high load pulling with a simple double-tap motion on the unit’s control switch located on the foot pedal.
Pullers like this are designed for commercial projects with several conduit sizes and pull lengths. The UT10-22 increases productivity for all applications featuring a no-load high speed of 16 ft./min. and is best suited for loads up to 4,000 lbs. where the speed will be 12 ft./min. If greater tension pulling is needed, the machine also has a setting with no-load low speed rated at 9 ft./min. suitable for loads up to 8,000 lbs. where the speed will be 6 ft./min., or a momentary peak capacity of 10,000 lbs.
Making Pullers Safer
After choosing the proper puller based on anticipated tension, contractors can make their task easier by turning their attention to the puller’s anchorage to the conduit inlet. Most pullers can be chained directly to the conduit or anchored on to slabs, but mounting pullers on adjustable frames is a growing trend.
When pullers are mounted on adjustable frames, they can be positioned to feed cable directly into the inlet at the same proper elevation and angle. Frames offer more protection for operators by allowing them to stand out of the pulling rope’s direct line. Many pullers also offer a foot switch that accomplishes the same goal of avoiding the pulling rope’s line.
By connecting a puller to Greenlee’s Mobile VersiBoom™ II, operators can quickly set up an ergonomically friendly pull in about two-minutes for any pulling situation. This combination of speed and versatility has been shown to increase productivity by delivering more pulls per day with the same crew size. These stands allow variable height settings and up-load feeds with a few easy adjustments.
Three Ways To Increase Puller Productivity
Along with properly sizing the puller to the task, Kester offers three suggestions to make the task safer and more efficient.
First, be sure to work within the puller’s design parameters.
“Never alter the cable puller,” says Kester.
Careful pre-pull management can improve planning and timelines. One new electrical tool that recently entered the design process is Greenlee’s BendWorks. This software application helps designers make sure all conduit runs are error-free by incorporating them into several BIM design tools. Contractors can expect less surprises for installation and pulling by using these systems and Greenlee electrical tools.
Second, Kester suggests always choosing the right rope for the pull. It’s tempting to grab spare ropes that are lying around to use for your next pull. But the size of a rope must have a corresponding capacity for allowable pulling tension. As an example, using a ¼-in. rope to install four 600kcmil conductors in a 400-ft raceway is just not practical. Even when the rope is applied correctly to a calculated pulling tension, checking the rope’s condition should be an every-day task. It has to be clean and dry, no kinks, knots, nicks or frays and should be stored where these conditions don’t occur.
And finally, make sure all accessories are rated equal or greater than the strength of the puller. Don’t forget that tapes often increase the diameter of the splice entering the raceway and create a less flexible section of the pull assembly through the raceway. The inflexibility caused by excessive tape use only makes cable passing through the raceway bends more difficult. Various cable clamping fingers (e.g., beckets, pull socks) are available on the market to secure cable to pulling rope – and that rope requires a perfect eye knot. The combination of eye knot and proper cable grip device (along with an approved and rated shackle) is ideal. Using this type of arrangement nearly eliminates tape use. The best way make sure you’ll be successful pulling cable is see that all accessories are matched for the task at hand.
As an example, for a 4,000 lb. cable tension installation, the puller choice would be ”G6 Cable Puller – rated for 4K – 6K lbs. The rope would need a tension rating of 6000 lbs. or more. And the grips must be rated equal to or greater than the strength of the puller. This example is the typical practice of “doing it right”, said Kester
A Word About Alignment & Electrical Tools
Always use rollers that allow spools to rotate in place and release wire smoothly for small cables. Jack-stands and cable reel arbors are typically used for large diameter cable installations and must have an adequate base dimension for stability. Jack-stand height should be enough to avoid the cable reel dragging on the ground. But be careful not to go overboard on height. Excessive jack-stand elevation will make the reel assembly top heavy and unstable.
Arranging multiple cable reels in-line or side-by-side for a single cable pull is a matter of personal preference or a consideration of site conditions. There are also electrical tools available for all multiple conductor pulls that dress and feed multiple conductors into a raceway without entanglement or crossing.
According to OSHA, more than 31,000 construction workers seek medical attention every year for sprains and strains suffered on the job. Pain from these injuries can last a lifetime and affect construction workers’ lives at work and at home. But these injuries are preventable.
OSHA has created a video on the benefits of using ergonomic practices while wire pulling to help electrical contractors make sure their crews don’t fall victim to this growing trend.
This video tells the story of an experienced commercial electrician who was wiring a newly built commercial building. He had been doing this kind of work for years, but after several days on the job, stress on his arms, neck, back and shoulders while using non-ergonomic techniques became too much for him to keep working at peak efficiency. In the video, safety experts offer their insights on events leading up to these injuries, and offer suggestions on how they could have been prevented.
Check out these links for more information on cable pulling:
To view the video, visit
An OSHA website, Ergonomics eTool for Electrical Contractors, has information on protecting electricians from injury – especially during installation. One sections shares insights on cable pulling tasks like Pulling Force, Frequency of Pulling and Feeding, and Overhead Reaching.
Take advantage of these resources by visiting: