NEC Requirements for 240/208 Volt Products

• Starting January 1, 1996, the NEC required that new construction (including remodeling) utilizes 4-conductor connections to 120/240 or 120/208 volt electric ranges, wall ovens, cooktops and dryers. Builders, remodelers, etc., cannot use 3-conductor power connections. 
• These 3-wire connections ground the frame of the appliance to the neutral conductor by means of a grounding strap (ground link) between the chassis and the neutral terminal at the wiring connection point. With the 1996 change, a separate ground wire from the junction box is required to ground the frame of the appliances. For installations with pig tails, it means the power cords have to have 4-pronged plugs.