This box fail to pass inspection

Discussion in 'Electrical Forum discussion & Blog' started by Ford2001, Sep 11, 2009.

  1. Ford2001

    Ford2001 New Member

    Messages:
    44
    Location:
    Manchester, Vermont
    Electrical inspector said that the 4"Sq. x 2-1/8 deep junction box what
    to small for the number of conductor inside it.

    Before I rip this box apart and replace it with a 4-11/16"sq. x 2-1/8 deep,
    why can't I just add 4"Sq. x 1-1/2" box exteneion ring?

    You should also know, that I plan to use a 4"Sq. box cover, 2-gang,
    raise 1".

    There is no local code in my area, all inspection are done by the State.
    The State used the NEC code 2008 editiion, with do not have a copy
    of at this time.

    Thanks
  2. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    996
    Location:
    NY State, USA
    Who said you can't? :confused:
  3. Jim Port

    Jim Port Electrical Contractor

    Messages:
    156
    Location:
    Maryland
    How many and what size conductors are in the box?

    Did the inspector also add the volume of the raised ring?
  4. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    If the inspector told you you needed a larger box then add the box extention...

    BTW...how many wires are in the box?
  5. Jim Port

    Jim Port Electrical Contractor

    Messages:
    156
    Location:
    Maryland
    The volume allowance is for a device, not an outlet. See the NEC definition of an outlet. The correct volume is for 2x the wire gauge attached to the device, ie 2 #14 = 4.

    Regardless of being insulated or not the ground still only counts as 1 volume allowance.
  6. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    996
    Location:
    NY State, USA
    All guesses, some wrong, and mostly erroneous.

    This part is mostly true.


    Ian, PLEASE try to refrain from posting stuff like this if you are not sure if what you are saying is correct.
  7. Ian Gills

    Ian Gills Senior Robin Hood Guy

    Messages:
    2,777
    Location:
    USA
    Sorry Petey I got carried away and made some awful and dangerous assumptions. Thank you for calling me out.

    I just checked some of my boxes and thanks for the ground wire clarification.

    But the whole process can be summarized this way, I think. But again, I don't really know what I am talking about and I am not an electrician.

    1. If conductors are the same size, add them together and size the box using the AWG size columns of Table 314.16(A). Your conductor equivalents will all be the same size as the conductors.

    2. If the box contains different sizes of conductors, use Table 314.16(B) to find the area of each conductor, add them up, and size the box from Table 314.16(A) using the cubic inch column.

    But please remember:

    1. Calculating box volume is a matter of adding up individual volumes of assembled parts [314.16(A)].

    2. Calculating conductor volume is a matter of adding up individual conductor equivalent volumes and there are five of these: 314.16(B)(1) through (5) [conductor volumes, cable clamp volumes, supporting fixture volumes, device yolk volumes and equipment grounding conductor volumes].


    If box fill exceeds box volume, then you need to reduce the number of conductors or use a larger box. You can add to the box volume the sum of individual volumes of assembled parts, such as plaster rings, extension rings, etc. You should however only include only those parts that are marked with their volumes in cubic inches [314.16(A)] or included in NEC Table 314.16(A).

    Keep in mind that these are minimum requirements. There's no penalty for using a box that's too big, other than the additional cost of that box versus a smaller one.
    Last edited: Sep 11, 2009
  8. Ford2001

    Ford2001 New Member

    Messages:
    44
    Location:
    Manchester, Vermont
    4" Sq. ext. box over a 4"Sq x 2-1/8 outlet box

    Your guys are great.

    I just got over a cold.

    But I want to give a big thanks to all, who took the time to reply to
    my Thread.

    Now I just new to replace all the brain cells I burn out when I was
    down with the cold. But your answer have really help me out. (humor)
    Last edited: Sep 20, 2009
Similar Threads: fail pass
Forum Title Date
Electrical Forum discussion & Blog Light Bulbs Failing Simultaneously Friday at 6:49 AM
Electrical Forum discussion & Blog Solenoid Failure? Nov 16, 2011
Electrical Forum discussion & Blog Submersible pump motor keeps failing Apr 12, 2011
Electrical Forum discussion & Blog 3 Way Switch power fails at Light Jul 9, 2008
Electrical Forum discussion & Blog Two F4T5/CW bulbs failed Jan 19, 2008

Share This Page