Box Size for a 3-way switch

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  #1  
Old 04-11-16, 08:08 PM
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Box Size for a 3-way switch

Iím trying to determine the right size box for a 3 way switch.

The two boxes will be on either side of an existing 2x4 drywall wall. Power feed will be from a light and 14 AWG, NMD-90 wire will be used.

The light is currently controlled by a single-pole, single-throw switch. This box will be abandoned as the box is in an inconvenient location on the wall. The current box is only 30 inches from the ground, and off to the side. A new more appropriately located box will be placed into the wall, and the existing 14/2 NM wire used for the new box. The other 3-way switch to be placed on the other side of the wall is new.
Here is the Box Fill calculation Iíve come up with for one of the boxes:
[TABLE="class: grid, width: 691"]
[TR]
[TD]#[/TD]
[TD]Item[/TD]
[TD]Allowance[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]1[/TD]
[TD]1 - 14/3 NM wire[/TD]
[TD]3 - 14 AWG[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]2[/TD]
[TD]1 - 14/2 NM wire[/TD]
[TD]2 - 14 AWG[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]3[/TD]
[TD]3 Ground[/TD]
[TD]1 - 14 AWG[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]2 cable clamp[/TD]
[TD]1 - 14 AWG[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]5[/TD]
[TD]Switch[/TD]
[TD]2 - 14 AWG[/TD]
[TD][/TD]
[/TR]
[TR]
[TD][/TD]
[TD]Total[/TD]
[TD]9 - 14 AWG[/TD]
[TD][/TD]
[/TR]
[/TABLE]

Volume Allowance: 9 x 2 cu in (14 AWG) = 18 cu in

Is the minimum size box that will be needed 18 cu in?
 
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  #2  
Old 04-12-16, 09:07 AM
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Your figures look accurate.
 
  #3  
Old 04-12-16, 09:23 AM
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When you do electrical work.... try to go with the largest (deepest) box you can fit. I specifically use deep cut-in metal gems and plastic boxes unless the wall is shallow and there is an issue.
 
  #4  
Old 04-12-16, 02:52 PM
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Boxes

Stagger the boxes on each side of the wall so the boxes will not be back-to-back. This will allow you to use a deeper box.
 
  #5  
Old 04-13-16, 02:56 PM
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thank you, much appreciated
 
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