Replacement Bus Plugs Properly Installed
Previously MIDWEST discussed the problem of making certain the disconnect fingers lineup properly when you replace a bus plug. We really didn’t answer the question of how to make sure replacement bus plugs are connected properly. Here are a couple suggestions. Put a very thin film of proper contact lubricant on the contact surface of the old bus plug disconnect fingers. Install the bus plug on to the bus duct. Note the position of the replaced bus plug and how it went into place. Then remove the bus plug and closely inspect the contact surface of the disconnect fingers. The film of contact lubricant should reveal that the disconnect fingers properly slid, ie wiped, on to the bus bar in the bus duct. Remove any excess lubricant. In addition, one can inspect the bus bars of the bus duct and see visible evidence that the disconnect fingers of the replacement bus plug actually wiped the surfaces of the bus bars correctly. After having verified the bus plug had been properly installed, install it again in the same manner as the first time. All this should not be necessary, but sometimes old or obsolete bus plugs are difficult to tell if they connected properly. It can be especially difficult when installing some large bus plugs. The physical effort to get them in place impedes the ability to sense if they went into place properly. Follow the manufacturer’s instructions on the possible use of contact lubricant. Regardless, too much lubricant is a mistake because it collects dust. Also, if new, reconditioned or repaired bus plugs are installed in a previously empty space on the bus duct, you should be able to see the contact wipe marks on the bus bar the first time the bus plug is installed or see new wipe marks on the disconnect fingers of the bus plug itself. All this is a simple way to give greater confidence the bus plug is installed properly. For safety reasons, MIDWEST strongly recommends this only be done on de-energized bus duct.