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Square D I-Line Molded Case Breakers

April 9th, 2010

What is it about these breakers that people like so much? In a word, simplicity ─ they are quick and easy to work with.


Most breakers such as the Cutler Hammer EHD3100, to give one example, use “details” (mounting bus details) to attach the breaker line side to the panel board bus. Details are an additional item at a slightly greater expense and are not necessary for Square D I-Line breakers.  I-Line breakers line side connections are finger clusters which connect directly onto the panel board bus making swapping out an I-line breaker as easy as drinking a cup of coffee in the morning.


The process is pretty straight forward:


First up, de-energize the panel board and lock out and tag out the switch supplying power to the panel board. Check voltage to make sure the panel board is dead and that it is not being back fed through another source. Remove the panel board dead front. Loosen the load side lugs and remove the load side cables from the breaker. You now have access to the single mounting screw holding the I-Line breaker in place. After removing the mounting screw, place a screw driver in the prying slot on the mounting bracket on the load side of the breaker and pry the breaker horizontally away from the bus running vertically down the center of the panel board. The breaker can now be removed from the panel board. Put the new I-Line breaker in place and using a reverse prying motion, slide the breaker horizontally into position such that the line side finger clusters make complete contact with the bus. Insert the mounting screw and tighten firmly. Do not over tighten this screw as it is a sheet metal screw designed to hold the breaker in position only. Reconnect the load side cables, then go ahead and install the dead front back onto the panel board.


At this point it’s always a good idea to exercise the breakers in the panel board, working the action by opening and closing the breakers several times. With the breakers in the off position in the panel board you are now set to power back up.

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