I've always enforced the need for a properly sized J-box for splicing fixture wires to the branch circuit conductors and not permitted the installer to rely on the canopy for this purpose. Am I wrong?

Up to 4 #14 or smaller fixture wires aren't counted in box fill anyway, so a box that is properly sized for the branch circuit conductors is sufficient. See 314.16 (B)(1) Exception.

410.10 Space for Conductors
Canopies and oulet boxes taken together shall provide adequate space so that luminaire (fixture) conductors and their connecting devices can be properly installed.
The italics are mine.

Thanks for your insight. I guess I'll will take a different view of this subject thanks for the code reference. I still am kinda nervous about allowing someone to install a 3" pan box with two 14/2 w/g for connection of a luminaire. I think I'll ask him for some specs on the proposed fixture, I'm sorry, luminaire.

George

The exception that Scott (electure) posted above applies to the fixture wires not the branch circuit conductors. Using a 3/0 pancake box with even one 14-2 NM cable is a violation unless the box is extended with an extension ring or canopy that is marked with its cubic inch capacity. I have never seen a fixture canopy that has been marked with its capacity. A single 14-2 NM cable would require a minimum of 6 cubic inches if an external clamp is used or 8 cubic inches if an internal clamp is used. A 3/0 pancake has a 4 cubic inch capacity. Two 14-2 NM cables would require 10 cubic inches with internal clamps or 12 cubic inches with internal clamps.

Curt

When I inspect I allow (1) 14-2 NM cable in a 3-0 pancake box. I realize that it is not permitted, but I also realize that sometimes that is the only way you can go about the installation. I will not, however, allow (2) 14-2's or (1) 12-2.

Actually, electure, those four fixture wires you refer to have to be SMALLER than #14 (not "14 or smaller") in order to avoid using them in fill calculations. See: 314.16(B)(1)

Ryan,

Why don't they use 4" pancake boxes instead of the 3". I have only seen the 3" on very old work like K&T. Is this a regional thing?

Hi Jim. I wish I could answer your question, but I'm afraid that it is a question I also ask. I can't figure it out. :0

If the installation of a 4 inch canopy on a 3 inch box is performed where the surface is combustible, it is a violation of 410.13.

Pierre

Triple,
Thank You! Sometimes I suffer from "Hoof in Mouth" disease.

Smaller than #14...S