Mike Dolt Enterprises
Mike Dolt Enterprises
User: Rutherford, Location: New York Adirondack region
Asked on: Friday, March 25, 2011 at 7:47 am EDT
Answered on: Tuesday, May 14, 2024 at 3:15 am EDT
Question: Two jobs ago, I directed an electrical contractor to not drill floor joists in a partial crawlspace, and to figure another method for running the branch circuit wiring perpendicular to joists. He screwed a 2x12 to the bottoms of joists, and stapled his Romex to its bottom face, jumping up into joist bays as required. His inspector said OK.I'm wondering if the dropped floor beam, shown in the pic here, can be used in the same way, to avoid much of the joist drilling.I've read 300.4 (D) and cannot get an interpretation one way or another.
NEC 300.4 (D) Interpretation
NEC 300.4(D) states that "concealed knob-and-tube wiring shall be installed as specified in 300.4(D)(1) through (D)(4)". Subsection (D)(4) allows knob-and-tube wiring to be installed in "other concealed locations where the location of the wiring can be determined by probing or exploration".This provision does not specifically address the use of dropped floor beams for concealed wiring. However, it can be interpreted to allow such use if the following conditions are met: The location of the wiring can be easily determined by probing or exploration. The wiring is not subject to physical damage or concealment behind panels or other obstacles. The dropped floor beam provides sufficient space for the wiring to be installed without causing damage or creating a fire hazard.
Dropped Floor Beam Application
In the case of the dropped floor beam shown in the photo, it is possible to use the beam to support concealed wiring if the above conditions are met. The beam provides a flat surface for the wiring to be stapled or secured, and it is easily accessible for probing or exploration.However, it is important to consider the following additional factors: The wiring must be protected from physical damage by nails, screws, or other fasteners that may be driven into the beam. The beam must be strong enough to support the weight of the wiring and any associated devices or fixtures. The wiring should be labeled or identified in a way that makes it easy to locate and identify.
Conclusion
While NEC 300.4(D) does not specifically address the use of dropped floor beams for concealed wiring, it can be interpreted to allow such use if the location of the wiring can be easily determined, the wiring is protected from damage, and the beam is strong enough to support the wiring and any associated devices or fixtures. Flag for review