ECN Forum Forums Photo Discussion Forums Photos for General Discussion Box Fill? ... This Box is Full!

Box Fill?
Just for fun I figured it.
(guessing from the pic)
4 x 1 1/2sq box = 21 cubic in.
10 #14's (10x2) = 20
2 #12's (2x2.25) = 4.5
2 #16gnd's (1x1.75) = 1.75
2 devices (4x2.25) = 9
Total = 35.25
Slightly overfilled!
BTW I see 2 wirenuts, that make 8 or 9 counting all of us critiquing this box.

lwinter31,

As one wirenut to the rest. . . . . ., remember, the box was calculated (if it actually was) when devices only counted as one conductor. Deduct 4.5 in³.

The reduced ground was manufactured for compliance with the '62 NEC grounding of all receptacles, but ground wires weren't added to the volume calculation until the '68 NEC was adapted (which is also the same time that the ground wire went full sized). Deduct 1.75 in³.

The cable and BX clamps, together, count as one conductor. Add 2.25 in³.

Adjusted wire space needed: 31.25 in³.

Box capacity is adjusted be (1.) the raised cover that we don't see (in the photo above) adding an additional 7.3 in³ (from Raco catalog).

And, (2.) another interesting twist, 2002 NEC Table 314.16(A), or its equivalent, was not introduced in the NEC until '68, in a totally reworked Table 370-6(a-1). In the '62 NEC, 4" X 1½" box could hold 11 #14 conductors, implying a volume of 22 in³, see '62 NEC Table 370-6(a-1). Therefore, I suggest adding another 1.0 in³ to the box capacity.

Total box capacity = 29.3 in³.

By my calc, the box is overstuffed by 1.95 in³.

Al

Edited for '62 NEC Table 370-6(a-1)

[This message has been edited by ElectricAL (edited 01-15-2003).]

Thanks Al
I gotta find some of the 60's & 70's codes.

I smooth forgot to calc the raised cover.

I thought the connectors were not counted if the "clamp" was outside the box. Was this different in past codes also?

Larry

I they didn't want you to put in so many wires, they wouldn't make em' with so many knockouts!

Yep, it had the raised cover.

Thanks for the info on the smaller ground conductor--I recall reading about that in Old Electrical Wiring Maintenance and Retrofit by David E. Shapiro.

This seems a good example of how the NEC has evolved from the 60s through the current edition.

ElectricAL: you get first prize for all of the calculations and references to the '60s codes.

Question about counting the clamps in the box fill:

Are you saying that the BX clamps and the two Romex clamps on the bottom, in toto equal one conductor? I know that such is the case relative to ground conductors.

Also, were the burial depth requirements for UF any different in the mid 60s?

Do any of you try to re-use the armored cable in such situations? (If that is permitted per NEC, that is.)

This reminds me of those "guess how many marbles are in the jar" contests.

P. S. lwinter31 is the runner-up, for now. I will need to count conductors out and double-check the AWG to verify

Larry

Thanks, the clamp outside the box doesn't count. So the space required for the conductors drops by 2.25 in³ to the new adjusted total of 29.0 in³. Can ya dig it! The box has 29.3 in³ capacity . . .it's "not over filled"!!!

Al

I still wrap conductors around the terminals without cutting them in the case of multiple devices in a box. One less splice, one less wirenut to contend with. (Mine don't come loose, though).
I used to keep track of the # of wires I'd seen in boxes. The record was 32-#12 in a 4Sx1-1/2, with a blank "sort of" on it.(not installed by me of course) I quit ordering 4S-Spl boxes for the crews because of their tendency to pervert them.

electure:

That box with 32 #12s in it should have had a warning about the cover flying off when opened

Are 4-square extension boxes OK to be "stacked"?

Code aside, I don't see a problem with wrapping a conductor around the terminal screw uncut, and continuing to another device. The terminal was designed to securely clamp a single conductor, and that's all it's doing.

The extra black wire that somebody's tried to add is a definite no-no, however.