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Long and short Madison Bars with old work metal outlet boxes

Installing An Electrical Receptacle Box Using Madison Bars

Dear Mr. Electrician: How do I go about installing an electrical receptacle box 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: Installing an electrical receptacle box using Madison Bars is a simple method for mounting certain types of metal electrical outlet boxes in a wall.  They are also known as Old Work Box Mounts, Support Clips, F Clips, Madison Clips, and Madison Straps. NOTE: Some text links below go to applicable products on Amazon or eBay.  As an Amazon Associate, I earn from qualifying purchases. The photo above shows Madison Bars, which are two different lengths.  The longer ones work in walls with double drywall or a finished surface such as tile or paneling that makes the wallboard thicker. In addition, screw clips are shown that can also be used to attach metal outlet boxes to the wallboard.  They 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. 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 multiple-gang wall plates from an electrical supply company, but you may be limited in choosing colors and styles.  I have found it best to limit your gangs to four when possible to find wall plates easily.  Over four gangs usually must be specially ordered. Decora style switches, outlets, and combination devices have the same style outlet cover, making it much easier to find wall plates that fit. 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 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 number of wires and devices contained within. It is important to have the hole cut exactly right when installing an electrical outlet box using Madison Bars.  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...