Thinkgood both items you show are good for surface installations.

For recessed or flush installations

30 amp we use a 4"sq Deep box with a two gang "plaster ring" that makes a 4" sq box have the front dimensions of a two gang box but leaves more volume for conductors in the rear.

50 amp we use a 4 11/16" sq Deep box with a two gang "plaster ring" that makes a 4 11/16" sq box have the front dimensions of a two gang box but leaves even more volume for the larger 50 amp conductors in the rear.

This may seem like overkill but when putting in the devices it goes much quicker and there is no question of having the required conductor space.

Do not forget that 300.14 requires 6" free conductor and on a box of this size 3" outside the box, using 6 AWG on the 50 amp outlet makes getting this much conductor in the box a bit tough.

99% of our work is commercial, the only boxes we use are 4" deep and 4 11/16" deep boxes.

To that we add plaster rings single, double, round etc.

The boxes have no mounting bracket we use Caddy H-23s
[Linked Image from erico.com]
The one on the right is as close as I could find to how we do it, plaster ring / Caddy bracket / 4" sq box

Caddy

Bob


[This message has been edited by iwire (edited 08-16-2003).]

Bob Badger
Construction & Maintenance Electrician
Massachusetts