Maintenance of Your Bus Duct Distribution System
Square D Bus Plug
It is always a good idea to de-energize bus duct before you install or remove a bus plug. If the plug is heavy it can be difficult to engage or disengage across all three phases at the same time. The result is you could partially engage one or more of the phases and twist or bend the connection point. This could result in subsequent hot spots which could lead to failure.
You also have to consider that this failure would occur on the line side of the bus plug where the current and hazards are much greater rather than the load side, where the amperage would be much lower. Want easy proof? Consider 200 amp bus duct with ten, 30 amp bus plugs (each fused at 20 amps). The problem on the line side of any one of the ten, 30 amp bus plugs is really a problem on a 200 amp piece of equipment. The same goes for removing a plug with the bus hot. The plug may be dirty or greasy and harder to control as you try to close it in or withdraw it from energized bus. Better to move the plug with the bus turned off.