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Long and short Madison Bars with old work metal outlet boxes

Installing An Electrical Outlet Box Using Madison Bars

Dear Mr. Electrician: How do I install an electrical receptacle box in a wall using Madison Bars?  I want to install an electrical outlet on a dedicated circuit for my window air conditioner and someone told me to use Madison Bars to mount the outlet box. Answer: Madison Bars are a simple method for installing a gangable metal outlet box in a wall.  They are also known as Old Work Box Mounts, Support Clips, F Clips, Madison Clips, and Madison Straps.  The photo above shows Madison Bars that are two different lengths.  The longer ones are for working in walls that have double drywall or a finished surface such as tile or paneling that makes the wall board thicker. In addition screw clips are shown that can also be used to attach metal outlet boxes to wall board.  They just clip on with a little force.  Once the box is in the wall, you tighten the screw and the clips wedge themselves between the box and the inside of the wall.  You can also buy some outlet boxes with the clips built-in. In the example below the hole was made using a Compass saw.  The metal outlet box was held against the wall and a pencil line was traced onto the surface.  Note the notches on the upper right and lower left corners.  They are to allow for the protruding screws on each side that all gangable metal receptacle boxes of this type have.  NOTE: Text links below go to applicable products on Amazon.com The boxes are gangable by removing one or both sides and screwing the boxes together with additional boxes to make a multi-gang switch or outlet box.  You can add as many gangs as needed, however the more gangs, the more difficult it will be to find wall plates to cover the finished work.  You can special order larger wall plates from an electrical supply company, but you may be limited in the choice of colors and styles. For the hole above I held the face of the electrical box against the wall and penciled an outline to follow with my Compass Saw. Installing an Electrical Receptacle Outlet Box using Madison Bars The ground wire above is attached to the box using a separate 10-32 ground screw.  Consult Article 314 in the National Electrical Code for the correct size electrical box needed for the amount of wires and devices that will be contained within. It is important to have the hole cut exactly right.  If the hole is too big the ears on the electrical box will not hold against the wall as the Madison Bars will pull the box inward. The ideal location for the new outlet box is next to a wood wall stud.  In that scenario I will drill a 3/16" hole about midway back on the side of the outlet box that will be against the wood stud.  After I install the Madison Bars securely I will screw a #8 x 1 1/4" sheet metal screw into the wood stud.  Do...