Siamese Junction Boxes

Need a code please. What prohibits the practice of combining junction boxes?

Hi Joe,
No issue here… Box extenders are not prohibited. The box attached to the top of the other one is just an extender – same kind of a box, but without a bottom. Peek inside if you want.
They are commonly used to avoid violating the box fill quota (too many conductors entering the box of too small a size), or just to make wiring easier with thicker gauge wires.

There isn’t one. Listed extension collars are permitted to increase the volume of a box. From the NEC:

Nothing prohibits that extension, that I know of…:slight_smile:

That’s a 1900 box extension.


How 'bout this one? :slight_smile:

[quote=“jfunderburk, post:6, topic:85693”]

How 'bout this one? :slight_smile:

Yeah… this one takes the cake :slight_smile:
NEC says:
NEC 110.12. Mechanical Execution of Work. “Electrical equipment shall be installed in a neat and workmanlike manner”
This one is neither neat nor workmanlike…

Thats the OCTAMOM of junction boxes and not the siamese!

lol. Nice one, Joe. I guess they had more J boxes than conduit!