Bus Plugs Blog – Expert Safety and Usage Information

MIDWEST frequently is asked how we can tell if an overheating problem in an electrical bus plug, found using Infrared Thermography, is a connection problem or a load problem. Especially when the bus plug cover can not safely be opened.  Overheating from a load problem usually displays a paintbrush effect on the bus plug enclosure. Large and continuous areas may display a higher temperature pattern. Looking at the electrical bus plug from different angles may still display a wide pattern of overheating and no indication of a spot source. This is difficult, even for an experienced Thermographer. MIDWEST’s Thermographers have the advantage of extensive training and experience reconditioning, maintaining, repairing and testing bus plugs in our switchgear shop. With this experience, they know the location of the internal components of the various bus plugs, whether Square D, Cutler Hammer, GE General Electric, Westinghouse, ITE Bulldog, or Federal Pacific. The combination of this knowledge and experience and their understanding of Infrared Thermography, gives them the tools they need to best differentiate between overheating due to load and overheating due to a poor connection or contact.

A connection problem may display a more localized heat pattern that sometimes can be confirmed by Infrared Scanning the bus plug from different angles.  The heat pattern at each angle may confirm the heat is coming from the same somewhat specific location.  With the cover closed, it is very difficult to identify the exact location. It might be the fuse clip or the lug for a feeder cable or the switch or breaker contact.

Finally, when possible, measuring the load on the bus plug feeder, when safe, and comparing it to the bus plug rating can help validate whether the problem is load or connection. Only when safe, the bus plug cover may be opened and an accurate scan of the inside of the bus plug performed.  It is not always possible to determine the exact cause of overheating in a bus plug, but these are some of the tools that increase our success.

We were looking for bus plugs and met Orville and Wilber Wright.  Well, sort of.  MIDWEST was in Dayton, Ohio, looking at old used bus plugs in a former manufacturing facility.  A big place.  A thousand bus plugs.  They had used Square D, ITE, and ITE Bull Dog bus plugs. They had used bus duct and bus plugs throughout the entire facility. We found bus plugs in all the manufacturing areas and above the ceilings in the offices, even the executive office. The facility had evolved and expanded over ten decades. There was a century of history in this manufacturing plant.  We found electrical infrastructure every where, behind walls that had been added or moved, above ceilings that had been remodeled many times, hidden in closets, and secreted away in basements long forgotten.  We were especially surprised to find a solemn plaque in front of a very old building, a hundred years old that had been beautifully remodeled inside as executive offices.  We were looking at old electrical bus plugs and transformers in an area of the building, walked out the front door to find the plaque that read, in part, “…these buildings were constructed in 1910 and 1911 to house the factory of Wilbur and Orville Wright’s first airplane company, The Wright Company.”  Now that’s a paradigm shift.  One moment it’s just an old building.  A second later it’s the Beginning of Manned Flight.  Today we have “Human Spaceflight.”  But we also still have bus plugs, some new and some old and some no longer used.