In this episode, Russ puts the size of this junction box to the test, and it fails. According to 314.28(A)(2) of the 2011 NEC, the junction box is too small for this application.
Discuss this Video 8
Russ:I enjoy your MV episodes very much,but this one is very confusing I see a 2"&1 1/2" raceway not a 3 and 4in. do we have to multiply by 2 somewhere???
You are right - in general. But, it needs to check the size and quantity of the wires that come into JB. According to 314.28(A)(3): "Smaller Dimensions. Boxes or conduit bodies of dimensions less than those required in 314.28(A)(1) and
(A)(2) shall be permitted for installations of combinations
of conductors that are less than the maximum conduit or
tubing fill (of conduits or tubing being used) permitted by
Table 1 of Chapter 9, provided the box or conduit body has
been listed for, and is permanently marked with, the maximum
number and maximum size of conductors permitted." It is common that 24" distance can be OK.
Rich,
The raceway sizes were correct. A 4 inch and a 3 inch on the right side of the box. The raceways on the other side were smaller.
Bigpower,
You make a good point, however, this J-box was not marked with any maximum conductor sizes or quantities.
By inspection, without a tape measure, this box fails. For a straight thru box, the minimum dimension is EIGHT times the largest raceway. For a turn, it is 6 times.
Russ i agree with you about the box size. It appears to me it's a strieght pull which would require 8 times the largest conduit size.
I agree with Pete it appears to be a straight pull..
You are correct in saying if it were a straight pull it would require an 8X dimension to the opposite wall.
However, when splices are made, as in this installation, the dimension is 6X plus the sum of the other raceway diameters.
in looking a the video . I am impressed with the information but immediately became aware of the presence of a metal measuring tape . when dealing and expounding safety we must also use safe materials in our presentation . what if there were live parts to touch ?
