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Old Work Box 1-Gang 18 cu.in.

Larger cut-in box for retrofit installations with more conductors.

18

cu.in. Volume

9

Max 14 AWG

8

Max 12 AWG

3" x 2" x 3-1/2"

Dimensions

Conductor Capacity per NEC 314.16

Maximum number of conductors that can fit in this 18 cu.in. box based on wire gauge (not accounting for devices, clamps, or grounds).

Wire GaugeVolume EachMax Conductors*
18 AWG1.5 cu.in.12
16 AWG1.75 cu.in.10
14 AWG2 cu.in.9
12 AWG2.25 cu.in.8
10 AWG2.5 cu.in.7
8 AWG3 cu.in.6
6 AWG5 cu.in.3

*Theoretical maximum for conductors only. Actual capacity will be less when including devices, clamps, and grounding conductors.

Common Applications

Complex remodel wiring
Multiple circuit retrofits

Calculate Box Fill for Old Work Box 1-Gang 18 cu.in.

Use our free calculator to verify your Old Work Box 1-Gang 18 cu.in. meets NEC 314.16 requirements.

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4-11/16" Square x 1-1/4" Deep

4-11/16" x 4-11/16" x 1-1/4" • 25.5 cu.in.

Octagon Box 1-1/2" Deep

4" Octagon x 1-1/2" • 15.5 cu.in.

About the Old Work Box 1-Gang 18 cu.in.

The Old Work Box 1-Gang 18 cu.in. provides 18 cubic inches of volume for electrical connections. This pvc box is commonly used for complex remodel wiring, multiple circuit retrofits. With dimensions of 3" x 2" x 3-1/2", it offers adequate space for most residential and light commercial applications.

Box Fill Calculation Example

For a typical installation using 14 AWG conductors:

  • Box volume: 18 cu.in.
  • 14 AWG conductor volume: 2.00 cu.in. each
  • Maximum conductors (theoretical): 9

Remember to account for devices (2× conductor volume each), internal clamps (1× conductor volume), and equipment grounding conductors (1× conductor volume for all grounds combined).

Practical Example: Receptacle Installation

Installing a duplex receptacle with two 14/2 NM cables in this box:

  • 4 × 14 AWG conductors = 4 × 2.00 = 8.00 cu.in.
  • 2 × grounds (count as 1) = 1 × 2.00 = 2.00 cu.in.
  • Internal clamps = 1 × 2.00 = 2.00 cu.in.
  • 1 × receptacle = 2 × 2.00 = 4.00 cu.in.
  • Total: 16.00 cu.in.

Result: 16.00 cu.in. ≤ 18 cu.in. = COMPLIANT

Related Resources

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