How to Install Dimmer Switches . Installing a dimmer switch? The National Electrical Code now requires larger box sizes to accommodate bulky devices like dimmer switches and ground fault circuit interrupters (GFCIs). If your home was built before the early 1990s, you may need to install a larger box when you replace a standard switch with a dimmer. This article explains capacity requirements, and shows how to remove an old electrical box and install a larger one without damaging the wall. www2.familyhandyman.com
