Bus Plugs Blog – Expert Safety and Usage Information

During an Infrared Scan, or Thermographic Scan, of the electrical distribution system of a new account, MIDWEST’s Thermographer noted in his report a strange bus plug set up. A 200 amp Cutler Hammer bus plug had a 2 inch pipe installed right in front of the cover. The pipe was 3 inches from the bus plug cover and right near the operating mechanism. The pipe was just kind of hanging there. It didn’t have much support. It went to a huge molding machine near the Square D bus duct. So you couldn’t switch this 200 amp Square D bus plug from the floor and you couldn’t open the cover of the bus plug, if you had to, because of the pipe.  Who in their right mind would do this?  As it turns out, they had an emergency and had to get a temporary line to the molding machine as fast as possible. Apparently the line carried plastic used in the molding machine and this machine was their main money maker. So they just installed pipe temporarily as quickly as possible. And six years later, the temporary pipe was still there. It more or less had become permanent.  Temporary installations evolving into permanent, is not an unusual occurrence. In the real world, production rules.  And like it or not, the same rules that caused a temporary pipe installation, also prevent the permanent installation. In the electrical equipment world, this is somewhat self correcting when the equipment gets unhappy with a bang.  Bus plugs do fail if they are ignored too long.  Whether a GE General Electric, Square D or Cutler Hammer bus plug, it will eventually fail if ignored long enough. When these things happen, those temporary fixes come back to bite you.  

Here’s another odd but very dangerous circumstance that MIDWEST ran into during the field data collection for an Arc Flash Hazard analysis.  The customer had an old Square D bus duct run in the oldest part of their plant. It was actually a complex made up of several buildings, the oldest being a wood structure going back seventy years.  They had mostly Square D and General Electric bus duct and bus plugs, and a small run of ITE.  The old part of the plant was used for storage.  All the manufacturing equipment had long ago been removed. There were very few Square D bus plugs still being used in the bus duct in this area. There were maybe a dozen bus plugs that were still installed but no longer in use. In most cases, the pipe and wire feeder had been removed. But we found one 100 amp bus plug, no longer used, had a conduit going into a small room full of junk. We had been told the bus plug was off and the fuses probably removed. They didn’t know where the conduit went. When we checked, and we always check, we found the bus plug closed and hot, the feeder energized. The electrician was pretty surprised. We traced the conduit to a back small storage area, dark, no lighting, where it terminated in a 6 by 6 junction box on the wall right next to the door. This circuit was “deadly hot” because the cover was missing and the conductors were sticking out of the box, wrapped with the frayed remains of old cloth type tape. This was a deadly accident just waiting to happen.  When MIDWEST recommended turning off the old bus plug; removing the fuses; and removing the conductors and conduit from the bus plug, they balked. Thought just turning it off was okay. But, since this was an abandoned circuit, not to be used again, we always recommend removing it. We consider this a safe work practice that eliminates the possibility of something “deadly hot” injuring or killing someone in the future.