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# # of wires in j-box

#1
07-05-05, 12:28 PM
Member
Join Date: Oct 2004
Location: Derry, New Hampshire
Posts: 291
# of wires in j-box

Hi, I have a 4" x 4" j-box that has 10 #12 wires in it, (not counting grounds). This circuit is only used for bedroom receptacles and an adjoining study light fixture. Any problems with the amount of wires in the j box?
Thanks.

#2
07-05-05, 12:58 PM
Member
Join Date: Feb 2005
Location: Harrisonburg
Posts: 744
Bob,

We would need to know the depth of the 4 x 4 box. In other words here are the number counts for listed boxes.

1.) 4 x 1 1/4 - 8 Conductors
2.) 4 x 1 1/2 - 9 Conductors
3.) 4 x 2 1/8 - 13 Conductors

If none listed....look inside the box and it should be stamped with the total cubic inch.....now.....if it states the cubic inches...here is how you do the math yourself..

# 12 AWG equals 2.25 cubic inch per conductor entering the box.

(1) Conductor Fill . Each conductor that orginates outside the box and terminates or is spliced within the box shall be counted once, and each conductor that passes through the box without splice or termination shall be counted once.

Now....if you have a connector clamp inside the box it you will count as (1) # 12 AWG as listed above ( 2.25 cu in )....if they are outside connectors do not count them.

Since you state it is only a junction we wont go into yokes and hickeys and so on........

Solution for you...if you find the box is not large enough for the wires you have...simply add a box extention onto the box to give you more cubic inches....

But so you know what I mean......the (10 ) # 12 AWG wires have a CU rating using the table on 370-16(b) of 22.5 CU IN....and now you need to add (1) 2.25 cu in for the ground wires...they only count as one for calculations...so you over all have a volume of 24.75 CU IN of wires...( provided no connectors inside the box or clamps )......if you do you need to add another 2.25 to the math......

Again it is based on the Cubic Inch of the box itself....but extention boxes can help get around that issue....but never overfill.

#3
07-05-05, 01:17 PM
Member
Join Date: Oct 2004
Location: Derry, New Hampshire
Posts: 291
Thank you....the box is 2 1/8" deep. My clamps are on the outside, so I guess I am good.

thanks.

#4
07-05-05, 01:35 PM
Member
Join Date: Feb 2005
Location: Harrisonburg
Posts: 744
Bob,

Yeppers....if it is 2 1/8 then you are good to go........P.S. Don't forget to put a blank cover on the box....

And keep it accessible at all times.....and well you know the deal....

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