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In the Home Owner's electrical test, the term "environmental air" is used. What does this term mean, and where is it defined? and can you use a non-metallic box?

Also when reading the question do you read that the box is installed inside the duct or in the framing that the duct is in?

DMoore
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2 Answers2

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No.

Physically Constructed Ducts or Plenums

This would be the actual tube where HVAC air is moved through.

In a physically constructed duct or plenum, there is no wiring allowed unless it is necessary for the direct action upon, or sensing of, the contained air. Even then, nonmetallic boxes are not allowed.

Spaces Used for Environmental Air, Other Than Ducts and Plenums

This might be the area above a drop ceiling, or under a raised floor.

In this case, only specific things are allowed.

  • Type MI cable.
  • Type MC cable without an overall nonmetallic covering.
  • Type AC cable.
  • Factory assembled multiconductor control or power cable that is specifically listed for the use.
  • Listed prefabricated cable assemblies of metallic manufactured wiring systems without nonmetallic sheath.
  • Electrical Metallic Tubing (EMT).
  • Flexible Metallic Conduit (FMC).
  • Intermediate Metal Conduit (IMC).
  • Rigid Metal Conduit (RMC) without an overall nonmetallic covering.
  • Surface metal raceway, or metal wireway with metal covers, or solid bottom metal cable tray with solid metal covers.

Again, no nonmetallic boxes.

300.22(C)(2) Equipment

This section does not apply, since a junction box is likely not considered "Electrical Equipment" as far as this code section is concerned.

If you'd like to read the actual code verbiage, it can be found in my answer to this question.

This YouTube Video from Mike Holt on the subject, might also be worth watching.

Community
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Tester101
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"Environmental Air" seems to mean ducting/plenums for air conditioning/etc. 300.22(B) relates specifically to the ducts/plenums, while 300.22(C) is specific to the spaces around the ducts/plenums (ie ceiling spaces, wall cavities, etc).

I think you're looking for:

*300.22(C) Other Spaces Used for Environmental Air (2) Equipment. Electrical equipment with a metal enclosure, or with a nonmetallic enclosure listed for the use and having adequate fire-resistant and low-smoke-producing characteristics [...]

Also, this Q&A states in the last paragraph that:

Electrical equipment with metal enclosures is permitted to be installed in a cavity plenum space [300.22(C)(3)]. Examples of electrical equipment permitted in a cavity plenum space would be air-handlers, junction boxes, [...]

So, I revise my answer to, "Yes, provided that they have adequate fire-resistant and low-smoke-producing characteristics."

Jacob S
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