6

Working on a project where I am planning a 3-gang switch box. The box will be a plastic carlton super blue (53 in³). My fill-math works out fine, but I'm wondering about the practical reality of such a crowded box.

Box will contain:

  • 14/2 inbound power (4 in³)
  • 14/2 outbound switched-power to fixtures (4 in³)
  • 14/2 outbound switched-power to fixtures (4 in³)
  • 12/3 outbound to another switch box (6.75 in³)
  • 12/3 inbound from another switch box (6.75 in³)
  • 2 dimmer switches 14AWG (8 in³)
  • 1 4 way switch 12AWG (9 in³)

Total: 42.5 in³

If I did the math right - it seems to add up - but that's a lot of stuff - plus it seem odd to me that a dimmer that takes up a lot of volume is the same fill as a basic pole switch.

Am I going to have a hard time getting that all in and should I consider breaking up the switch boxes.

Note - that the 12 AWG is putting a 4 way into an existing branch that was wired with 12 AWG. 14 AWG is on a new circuit.

David K
  • 217
  • 1
  • 17
BlueGoldfish
  • 181
  • 7
  • 5
    Dimmers and GFCI's (and timers, and...) are bigger than "usual" but the box fill allows for them - but being anywhere near max fill tends to be tight. It's often worth a few bucks to use a larger-than-minimum box for your own sanity. **You don't appear to have counted your grounds.** They won't put you over max fill, though. (And the usual *opinion* that steel boxes are better in every way...) – Ecnerwal May 18 '22 at 10:30
  • 3
    I just did my first (very small) wiring project using Wago lever-lock connectors. Not only were they so simple that they were a joy to use, but they're physically smaller than a wire nut and will buy you back some space in the box. They won't impact the fill calculation (any more than your dimmers do), but they help with the reality. – FreeMan May 18 '22 at 12:50
  • 2
    Neatness counts for a lot in cases like this. For example, running a tidy backbone of grounds that stays back and low will help. – Aloysius Defenestrate May 18 '22 at 13:19
  • @Ecnerwal - the deep Carlton was the only 3 gang I could find with 53in capacity. Can I match that capacity in metal with some combination of box plus extension rings? I couldn’t find metal boxes that deep at my LHS. Correct on missing grounds - will add that in. – BlueGoldfish May 18 '22 at 20:46

1 Answers1

6

Dimmers do tend to be bigger than simple single pole switches. But if the fill calc is correct then it should be manageable— 53 cu in is a lot.

RibaldEddie
  • 2,072
  • 1
  • 7
  • 12