What size are deep boxes?

[EmagSamurai]

The electrical is almost done in my house, and I wanted to double check that they actually installed the "deep" wall boxes. However, I'm not really sure what size they should be. Some of the larger 3 and 4 gang boxes are 3-1/2" deep. The single gang boxes look like they are all 3" deep, I believe. So I'm wondering if the "deep" boxes should all be 3-1/2", or if they're different depending on whether it's a 1, 2, 3, or 4 gang box.

 

[standon]

They measure them in cubic inches. I think that old work single gang is 20 cubic inches while there are deeper 22 cubic in boxes for single gang - which is probably the 3 1/2" depth you are referring to while the 3" deep boxes are "Old Work" 20 cubic inches. The cubic inches are less when its multi-gang even though it will be 3 1/2" deep still. For example, one gang, two gang, three gang, four gang all have the 3 1/2'" deep dimension if the site is accurate. I think most electricians install old work when you ask for deeper boxes - mine did anyway.

 

[EmagSamurai]

It's been recommended on several occasions that putting in "deep" boxes is a good idea when building to make it easier to install automated switches later. What depth box does everyone have in mind with that statement? Is 3" enough, or should it be 3-1/2"?

Thanks!

 

[wuench]

3" is fine.

 

[Mr Spock]

FYI there are also "super deep" boxes available. Carlon makes them, its their Super Blue series. A 2 gang box is 35 cubic inches with a 3.5 inch depth. I used these 2 and 4 gang boxes recently when I installed LED lighting in my kitchen, which needed 24VDC. I got some switching power supplies from DigiKey and had enough room to fit the power supply in the back of the box and the Insteon switches in the front. Worked great.

But to answer your question 3" is enough in typical HA applications.

 

[EmagSamurai]

Thanks for the replies everyone! Looks like I've got boxes that range from just under 3" for single gang boxes to 3.5" for multi-gang boxes. So it looks like I'm good!