According to the National Electrical Code (NEC), the minimum box size required for receptacles in a kitchen depends on the number of conductors and devices in the box. The NEC provides guidelines to ensure proper spacing, wire bending space, and heat dissipation. Here's a general guideline for the box size based on the number of circuits and devices:
Single Circuit (20A): For a single 20A circuit, a standard 2-gang box with a minimum size of 4" x 4" x 2 1/8" (21 cubic inches) should be sufficient to accommodate the receptacle and its associated wiring.
Two Circuits (40A): If you have two separate 20A circuits in a single kitchen receptacle box, you would need a larger box to accommodate the additional wiring. In this case, a 3-gang box with a minimum size of 4" x 6" x 2 1/8" (30 cubic inches) or larger would be appropriate. This size provides enough space for the two receptacles and their associated wiring.
It's important to note that these are minimum size requirements. It's generally a good idea to choose a box size slightly larger than the minimum to allow for easier installation and future modifications if needed. Additionally, local electrical codes may have specific requirements or variations, so it's advisable to consult your local building department or a qualified electrician for the specific regulations and best practices in your area.