Box fill question

Reply

  #1  
Old 09-10-09, 06:21 AM
J
Member
Thread Starter
Join Date: Sep 2005
Location: Just outside of Phila
Posts: 350
Received 0 Votes on 0 Posts
Box fill question

I have a 21 cubic inch box that has 3 12/2 ga cables in it. The cables are wire nutted together with a pigtail to a receptacle. Do the pigtails need to be added as part of the total volume? If so is my math correct? With the pigtails = 21.25 cubic inch Without the pigtails = 14.5 cubic inch Will I need a new box or am I ok? Thanks, John
 
Sponsored Links
  #2  
Old 09-10-09, 07:03 AM
I
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,944
Received 43 Votes on 41 Posts
Pigtails don't count in box fill. The fill should be:

Count the fill units: 6 conductors + 1 grounds + 2 receptacle = 9 fill units

Multiply by 2.25 cu in for #12 wire: 9 * 2.25 = 20.25

The minimum box size is 20.25 cubic inches.
 
  #3  
Old 09-10-09, 07:22 AM
J
Member
Thread Starter
Join Date: Sep 2005
Location: Just outside of Phila
Posts: 350
Received 0 Votes on 0 Posts
ibpooks, thanks for the reply. I just learned something new. I understand the 6 conductors and adding 1 for all the grounds but I wasn't sure about the pigtails. I also didn't realize that you had to add the recep to the fill count. So I'm assuming that if it were a simplex recep that the fill count would be 8, correct? And if it were a light switch it would also count as 1? I have the 2005 NEC but couldn't find that info anywhere.

Thank you
John
 
  #4  
Old 09-10-09, 07:40 AM
I
Forum Topic Moderator
Join Date: Feb 2005
Location: Near Lansing, Michigan
Posts: 10,944
Received 43 Votes on 41 Posts
Any device (GFCI, receptacle, switch, etc) counts as 2 units. NEC Article 314.16 covers box fill; there are several sub sections which list the details of the calculation.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: