Reaction vs Precaution: Karl Beckmann, J & J Electric, and the Impossible Pull

Aug 22, 2017

Karl Beckmann has been on the Contractor Solutions team for years now and has been part of many complex installations. Now, Beckmann has seen the contractors at J &J Electric go through the most complicated installation in his career and had to write in about what he saw.

J & J Electric is doing an upgrade to the electrical system at a commercial building in the Midwest. As part of this project they have several feeder runs from the electrical room up over the rooftop and back down. They were concerned that these pulls would be difficult given the length, number of elbows, vertical rise and fall, and size of copper conductors. I walked the jobsite with Tom Fanning of J & J Electric to get the details for the wire pull, then did the pull calculations based on what they knew at the time. (They did not have the last couple 90 degree elbows installed in the electrical room at the time.) The pull calculations indicated the pulling tension would not be a concern, but the sidewall pressure would have exceeded the 1000 lbs. recommended by around 250 lbs (This was for the SIMpull THHN® Copper 600V Kcmil. The SIMpull THHN® Copper 350V Kcmil was fine.) I talked to Tom Fanning and John Nall from J & J about the calculations after I emailed them, and told them that if they were able to install 90 degree elbows in the electrical room with 24” sweeps instead of standard sweeps it would eliminate the high sidewall pressure and risk of insulation damage. They measured the available space and determined they had enough room to put in elbows with a larger radius that they would bend themselves. The estimated radius on the sweeps was 23”, which would be enough to lower the sidewall pressure to a safe level.

Another challenge to this project was the location of the ends of the conduit, which would determine where we would have to feed and pull from. Russ King, Ross Sexter, and I (all from Contractor Solutions) met with J & J and walked the jobsite to determine the best way to install the feeders. Russ King sent a detailed suggestion on where to pull from, feed from, equipment needed, etc. based on the information learned on our job site visit. Included in this was a suggestion to use the SIMpull™ Cable Guide System to guide the feeders into the conduit and over the HVAC duct that was in the way of the feeding location. Complicating this was the fact that there were rooftop HVAC units in the way, the associated piping, and large HVAC ducts. Also, we had to feed from the rooftop which we did not know the allowable load, but were fairly certain was not designed to support reels of cable. Given this, Russ recommended that Kirby Risk send the wire to J & J on wood reels on A-frames with SIMpull Head® Pulling Grips installed on both ends. The A-frames with the reels were set below near the side of the building, which allowed them to pull up over a sheave wheel and onto the rooftop. J & J also had to pull off an additional 125 ft onto the rooftop and backfeed into another conduit which went to the 2nd electrical panel. (They could not pull straight through in this case because of the sidewall pressure at the last 90 degree elbow in the electrical room where they were pulling from.)

They used the 9/16” QWIKrope® pulling rope, MAXIS® XD10 EXTREME Duty Cable Puller, swivel clevis, and SLIDEit™ Wire Protectors on this job in addition to the wire guide. It was not a perfect situation for the SIMpull™ Cable Guide System, but with the challenges on the feeding end on the rooftop I estimate it saved at least two people having to stand on conduit and feed the wire into the conduit. They still had 6 guys on the rooftop to handle the wire because they had to pull it up and over a sheave wheel held in place by the forklift. The purpose of this was to lift the cable up over the HVAC ducts in the way, then lay enough slack on the rooftop so as not to create additional back tension on the pull. On the first pull they ran the MAXIS® XD10 EXTREME Duty Cable Puller in low gear, and then on the second pull they ran it in high gear. The indicated tension (estimate) was very close to the 2,000 lbs. that we calculated.

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