Question 1. Are listed enclosures/ boxes required to house low-voltage equipment and devices in exterior locations, exposed to the weather? The project was designed and is being constructed under the 1993 NEC (1995 California Electric Code).

Background. A low-voltage personal alarm system is being installed. The system involves radio FM frequency locators and low-voltage repeater devices installed outside, exposed to the weather, in nonmetallic enclosures/boxes, and infrared transmitter devices installed in metal enclosures/boxes. The design calls for all the low-voltage interior and exterior wiring to be installed in conduit except where protected plenum wiring is applicable.

The “Personal Alarm System” is a security system which uses infrared (IR) and FM radio frequency (RF) reception and repeater equipment. The IRs are hard-wired. Most of the RFs are hard-wired, but some are powered by photovoltaics. The repeaters are hard-wired and relay signals to the control system. The system has been identified as Class 2 wiring under Article 725. We understand that Class 2 wiring is of such low voltage that it is exempt from Article 300, Wiring Methods; however, the project design requires (for protection from abuse, vandalism, weather and ultraviolet degradation) that the wiring and equipment be installed in conduit, boxes and enclosures. Even though Class 2 may be exempt, do Code requirements for listing apply to conduit, boxes and enclosures if they are used?

The manufacturer of the low-voltage equipment has provided unlisted nonmetallic and metal enclosures for their devices. The enclosures have been cited by the inspection agency as needing to be listed, with reference to NEC 110-3, Examination, Identification, Installation and Use of Equipment, and to 370-15, Damp, Wet or Hazardous Locations.

The manufacturer and designer have responded that listed enclosures are not required by the Code. They have cited 300-1(a), Exception No. 2, which states, “Only those sections referenced in Article 725 shall apply to Class 1, Class 2, and Class 3 circuits.”

 Article 725 includes Class 2 low-voltage wiring circuitry, and appears silent on conduit and enclosure requirements. The manufacturer and designer’s conclusion is that if not specifically addressed in Article 725, the requirements of Article 300, including 300-15, Boxes or Fittings – Where Required, do not apply. Therefore they maintain that Article 370 does not apply since 370-1, Scope, refers to 300-15. — M.M.

Answer 1.  According to the 1993, 1996, 1999, and 2002 NEC, 90-3, Code Arrangement, “...Chapters 1 through 4 apply except as amended by Chapters 5, 6 and 7 for particular conditions.”

Section 300-1(a), All Wiring Installations. This article covers wiring methods for all wiring installations.

Exception No. 2 states:  “Only those sections referenced in Article 725 shall apply to Class 1, Class 2 and Class 3 circuits.”  This exception was deleted in the 1999 and 2002 NEC.

Therefore 370-15 of the 1993 and 1996 NEC do not apply, but do apply in the 1999 NEC and under 314.15 of the 2002 NEC.

Since the project design requires more than the minimum code as stated, the authority having jurisdiction may exercise his authority under 90.4, Enforcement, by requiring 110.3, Examination, Identification, Installation, and Use of Equipment, to be followed. —Larry Chan, CMP-16

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Question 2. I am trying to find information regarding telecommunications conduit placement within a telecommunications room with regards to the placement of the electrical conduit within that same room. Does the NEC address this situation similar to what is found in NEC 800.10(A)(1)? For example: electrical conduit associated/not associated passing through a telecom room, is our conduit required to be below the electrical conduit? — S. W.

Answer 2.  The 2002 NEC does not address the situation given. No specific distances are required between the electrical and the telecommunications conduits — associated or not associated. A room housing telecommunications equipment and wiring is a building design issue. — Larry Chan, CMP-16

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