4 How To Inspect Electrical Conduits and Boxes


In Article " Conduit Fill Calculations ", I explained the following items:

  • Conduit Sizes Designations,
  • Tables used for Conduit Fill Calculations.

Also, In Article Electrical Boxes Volume and Fill Calculations ", I explained the following items:


  • NEC 314.16 Part (A): Box Volume Calculations,
  • NEC 314.16 Part (B): Box Fill Calculations,
  • NEC 314.16 Part (C): Conduit Bodies.



Today, I will explain How to Inspect Electrical Conduits and Boxes as follows.



You can review the following articles in the same course for more information:







Area Classification Requirements



  • As an Electrical Inspector, you must verify that all electrical equipment located in the classified areas meet the requirements of the NEC for use in that particular hazardous location.

  • Rigid metal conduit and type MI (mineral-insulated) cable are used in Class I, Division 1 locations.  Thread all conduits.  Termination fittings must meet approval if used with Type MI cable.  All boxes and fittings must be explosion-proof and have threaded openings.

  • Lighting fixtures used in these locations must meet approval for use by one of the approved testing laboratories.  Mounting boxes must be explosion-proof and approved for hanging and mounting fixtures.  Pendant fixture wiring must be in metal conduit and suspended from the ceiling.






Flame-Proof Junction Boxes


  • Seal conduit systems in Class I, Division 1 and 2 locations if sparks, arcs, or high temperatures could be present in enclosures containing electrical equipment.  The seals will minimize the spread of gases, vapors, and prevent the passage of flames from one part of the electrical system to another.  They will also prevent an explosion in the enclosure from traveling through the conduit or cables to other locations, causing additional fires or explosions.  If vapors in the conduit can condense into a liquid, provide drainage.









How to Inspect Conduit



Use this work Procedure as a guide to help you inspect conduit as follows:





  • Verify the fill percentage.
  • Verify that the conduit is properly supported.
  • Verify PVC coating, threaded lubricant is applied.  PVC patching compound must be on sleeves. 
  • Verify that the conduit connections are wrench tight.  Use a strap wrench for PVC-coated conduit.
  • Verify that the expansion joints are installed and bonded where needed
  • Verify that locknuts are installed and installed correctly.
  • Verify the installation of weatherproof hubs on outside installations.
  •  Verify that bushings are installed at boxes.
  • Verify that there is no more than 360 degrees of bend between pull points.
  • Verify that conduit is buried at the proper depth in underground installations.
  • Verify that conduit was reamed after cutting.
  • Verify that conduit threads are properly cut.
  • Verify that conduits are fireproofed where needed.
  • Verify that conduit bodies containing splices are completed in accordance with the NEC, Article 314-16(c).









How to Inspect Junction Boxes and Pull Boxes



Use this Work Procedure as a guide to help you inspect junction boxes and pull boxes as follows:





  • Knockout seals must close all unused openings in boxes or fittings.
  • All metal boxes are usually required to be grounded.
  • At least 6 inches of free conductors must be left at each outlet box. Three inches must extend from the edge of a box less than 8 inches in any dimension.
  • Conduits must not be connected to the sides of round boxes, only to square smooth sides.
  • Boxes may be recessed 1/4 inch or less for noncombustible material.
  • Each outlet box must have a cover, faceplate, or fixture canopy to complete installation.
  • Volume of original box may be increased by the cubic inches marked on the plaster ring.
  • All boxes used to install lighting fixtures must be designed so that a lighting fixture may be attached.
  • Boxes must be rigidly fastened to the surface upon which they are mounted.
  • Boxes shall not use suspended ceiling wire as a sole supporting means unless associated with electrical equipment designed for suspended ceilings.
  • Boxes mounted in a wall of combustible material must be flush with surface or project from it.
  • Junction boxes must be accessible without it being necessary to remove or disturb any part of the building. However, lift-out panels in suspended ceilings are considered accessible.







In the next Article, I will make a Review for Course WR-2: Inspect conduits, junction boxes, and pull boxes . Please, keep following.







4 comments:

  1. Flameproof Junction Box
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    Electrical Engineering Consultant

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