Is my junction box overloaded?

Question

What to do when the wires barely fit in the box? We got them to fit with a lot of fusing, but I'm not sure if that's okay or not. Lots of smushing down and the outlet covers don't fit flush on some. My concern is twofold - that getting all the wiring in there as fiddly and bent to make it fit will somehow make a dangerous situation. And if we just did it outright wrong and that's why it's not fitting.

Part of the problem: using GFCI outlets, surface mounted PVC and plastic boxes because this is in a wet location and I couldn't find any other boxes that were appropriate. 20amp circuit, so the wiring was fairly stiff.

Specifics: Big project this weekend to wire a fish room. As it is to be around water, went with pvc and plastic gang boxes and gfi on each outlet (at a wince-worthy expense) With the help of a friend who is not an electrician but has done a lot of cabling and electrical work, we installed 2 20amp circuit breakers in an empty panel, and 11 boxes with 22 GFI outlets using romex 12 gauge. I think this was the first time he worked with 12 gauge wiring though. We were actually able to make most of them fit, but there is a lot of wire in each box, and some of the outlets are sitting at odd angles because of the way the wire was put in there.

It might be fine, and with some more finessing get the ones at angles in there the rest of the way. But I want to verify it's okay, and if its not, figure out where and how to get deeper boxes to be used in a wet area. (I did see plenty of deeper boxes but not in an area that was meant to be surface mounted and weather resistant).

Answer 1

One option is to use a single gang mud ring for double gang box. you can get metal or plastic ones.

Answer 2

You can definitely get deeper boxes, and you can also get box extenders, but at some point you'll be limited by the depth of your walls and you'll need to use double-gang boxes to get more room.

Since you commented that you're using a separate GFCI for each fish tank, I presume that you're pigtailing the wires through the boxes, and not feeding downstream GFCI's through the upstream GFCI's?

Somebody else already mentioned the box fill chart in a comment. You can also find handy little box fill calculators on the web.

EDIT: The answer that suggests using a single gang mud ring for a double gang box is spot on, that's what I meant by going to double-gang boxes, and you can certainly get the mud rings in metal or plastic.

You can also get single-gang boxes with a behind the wall cavity to one side:

Are your walls open so that you could replace the boxes (relatively) easily with double-bang boxes? If you've already put the sheetrock up but haven't taped it yet, you could unscrew it and replace the boxes. If you use double-gang boxes with mud rings, just fill the gaps beside the boxes (where you cut the holes in the sheetrock bigger) with joint compound and tape over them.