I am doing preliminary design of the wiring for a shop to be built next year. The floor will have a concrete slab. I want to use the Leviton FBBOX system to put some outlets in the center of the shop to power a Table Saw and possibly other tools. My question : the FBBOX has a divider in the center. Per code, can I have 2 different circuits in the single FBBOX? I want to have a 120V 20A receptacle controlled by a 20A GFCI breaker in one half and a 240V 20A receptacle controlled by a 20A 2 pole breaker on the other half. This is all in conduit and will be connected by separate 12 ga THHN wires. Thanks!

  • 2
    If it's all 120/240 you don't even need a divider. A divider is needed when you have low voltage (network/TV/phone) sharing with line voltage. Unrelated, other than you haven't poured the concrete yet, do a concrete-encased electrode or Ufer ground when you do the concrete work. – Ecnerwal Jan 22 at 4:03
  • Thanks for the idea about the Ufer. I think I need 20' long rebar and I will have that. – Mike F Jan 22 at 5:50

For line voltage (120/240 - all 120V to ground, so basically the same voltage from a code perspective) you don't need a divider. A divider is needed when you have low voltage (network/TV/phone) sharing with line voltage.

Unless you are sticking in a 240/120 receptacle (like an L14-20) you'll only have one neutral, so @manassehkatz-Moving 2 Codidact's concern about keeping neutrals straight does not apply, but you will want to either use different hot colors or apply tape, paint, or heat-shrink (if using only one color) to keep the hots correctly grouped. You could use black & white for the 120V and red for both 240's (they don't need to be different from each other) or you could use 3 different hot colors and white (or gray) for the neutral. Or red-taped black for the 240.


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