I usually use plastic electrical boxes but I was looking at square metal boxes today and was wondering why they come in two sizes, 4 inch and 4 11/16 in. Why are there two sizes and when would you want to use one over the other?

 

Cubic capacity—where if you need more room, then go with the larger and deeper size box. Depending on the manufacture. The box could be made in China, New Mexico, or USA.

 

Thanks. I noticed one thing though. A standard wall plate won't cover a 4 11/16 box. I guess the oversized ones would.

 

They do sell mud rings for them. So you can attach a mud ring and install a device, with a standard device face plate. I never see the rings at the big box stores, but based on my search, they have them. I would only use them for junction boxes only. But, that’s me.

 

example [Note: You have to scroll down to see the picture on the link]:
Product Datasheet -- 837

 

Thanks, yes I did see some 4 11/16 mud rings on the Lowes and HD websites. I haven't looked in the stores yet.

 

I've found the same variety of mud rings manufactured for 4 sq. vs. 4-11/16 boxes. However the big boxes do not stock many for 4-11/16, whereas an electrical supply house should have everything from flat to maybe a 1-1/2" tile ring.

I use a lot of 4-11/16, but they typically are a bit more work to mount because they don't have the same bracket options as the widely-stocked 4 sq. boxes.

 

That's why both B-Line and Caddy make a complete line of accessories for electrical installations such as for mounting boxes, but I doubt you'll find them at a big box store.

H23 and MEB1