You just had to do it. Poke your wire right through the flex duct. Um… that is a no no. Let alone you now have poked a hole in you duct work you also installed the wiring in a non-compliant way.

300.22 Wiring in Ducts Not Used for Air Handling, Fabricated Ducts for Environmental Air, and Other Spaces for Environmental Air (Plenums)

The provisions of this section shall apply to the installation and uses of electrical wiring and equipment in ducts used for dust, loose stock, or vapor removal; ducts specifically fabricated for environmental air; and other spaces used for environmental air (plenums).

(B) Ducts Specifically Fabricated for Environmental Air.
Equipment, devices, and the wiring methods specified in this section shall be permitted within such ducts only if necessary for the direct action upon, or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to facilitate maintenance and repair, enclosed gasketed-type luminaires shall be permitted.

Only wiring methods consisting of Type MI cable without an overall nonmetallic covering, Type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering shall be installed in ducts specifically fabricated to transport environmental air. Flexible metal conduit shall be permitted, in lengths not to exceed 1.2 m (4 ft), to connect physically adjustable equipment and devices permitted to be in these fabricated ducts. The connectors used with flexible metal conduit shall effectively close any openings in the connection.

Exception: Wiring methods and cabling systems, listed for use in other spaces used for environ mental air (plenums), shall be permitted to be installed in ducts specifically fabricated for environmental air-handling
purposes under the following conditions:
(1) The wiring methods or cabling systems shall be permitted only if necessary to connect to equipment or devices associated with the direct action upon or sensing of the contained air, and
(2) The total length of such wiring methods or’ cabling systems shall not exceed 1.2 m (4 ft).

(C) Other Spaces Used for Environmental Air (Plenums).
This section shall apply to spaces not specifically fabricated for environmental air-handling purposes but used for air-handling purposes as a plenum. This section shall not apply to habitable rooms or areas of buildings, the prime purpose of which is not air handling.

Informational Note No. 1: The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies.

Informational Note No. 2: The phrase “Other Spaces Used for Environmental Air (Plenum)” as used in this section correlates with the use of the term “plenum” in NFPA 90A-2012, Standard for the Installation of Air-Conditioning and Ventilating Systems, and other mechanical codes where the plenum is used for return air purposes, as well as some other air-handling spaces.

Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.

From the Handbook- “This exception permits cable to pass through joist or stud spaces of a dwelling unit, where the joist space is used as a return for a forced-air central heating or air-conditioning system. As shown in Exhibit 300.20, the joist space is covered with appropriate material, and the cable passes through the space perpendicular to the vertical run. The exception does not permit equipment such as junction boxes or device enclosures within this space unless the wiring method employed and enclosure type used meet the requirements of both 300.22(C)(1) and (C)(2).”

From the Handbook- “Other spaces or plenums — such as the space or cavity between a structural floor or roof and a suspended (hung) ceiling — are used to transport environmental air and are not specifically manufactured as ducts. Many spaces above suspended ceilings are intended to transport return air. Informational Note No. 2 correlates the term other spaces used with environmental air with the term plenum as used in NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems”

This section does not apply to habitable rooms and other areas whose prime purpose is other than air handling and ordinary wiring methods are permitted in these areas. If the prime purpose of the room or space is air handling as depicted in Exhibit 300.19, the restrictions in 300.22(C) apply, whether or not electrical equipment is located in the room. Only wiring methods described in 300.22(C)(1) are permitted in such rooms or spaces.

So as you can see there are some rules when it comes to wiring in ducts and spaces for environmental air.

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If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

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NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

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