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Home > NEC > Code Basics > Sizing Junction Boxes

Sizing Junction Boxes

Learn how to perform this task quickly and correctly - every time

Oct. 1, 2008 Mike Holt | Electrical Construction and Maintenance
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Comments 4
The sizing requirements for pull boxes, junction boxes, handhole enclosures, and conduit bodies exist to prevent conductor insulation damage. Those requirements are in 314.28, and they apply to all conductors 4 AWG and larger (Fig. 1). To illustrate how these requirements prevent conductor insulation damage, let's consider two extremes in a straight pull situation. Suppose you have a 2-inch raceway
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Discuss this Article 4

mohammad (not verified)
on Jan 28, 2013

Best explantion I have been completey confused with these calculation .thanks I wish you could explain some other complicated parts of NEC .thanks

  • reply
Anonymous (not verified)
on Apr 24, 2013

What size box would I need if I have (3) 4" conduits coming in the back of the box and (3) coming out of the top of the box. Each conduit has (4) 500 MCM that will be spliced in the box. Is 36"x36"x24" adequate?

  • reply
Anonymous (not verified)
on Jun 14, 2013

what size juction box do i need ?
2-4 inch on top
4-4 inch on side
with 4- 4/0 in each conduit

  • reply
emjae (not verified)
on Jun 17, 2013

very clear explanation. thank you

  • reply
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