Design and Construction as an Integral Part of Equipment

DOE-HDBK-1092-2004

R&D work may require the use of wiring methods that are not anticipated in the NEC. These

methods may not be consistent with normal commercial and industrial wiring methods, and

should be reviewed by the AHJ for approval.

10.9.1.2 DESIGN AND CONSTRUCTION

10.9.1.2.1 DESIGN AND CONSTRUCTION AS AN INTEGRAL PART OF EQUIPMENT

If the AHJ determines that wiring is an integral part of an apparatus (e.g., instrumentation

interconnections), then the wiring methods used should be evaluated by the AHJ as

providing safe operating conditions. This evaluation may be based on a combination of

standards and engineering documentation where appropriate. Such an evaluation should

consist of an analysis of all stresses imposed on any electrical conductive elements,

including, but not limited to electrical, magnetic, heating, and physical damage potential.

The wiring methods selected must mitigate to the greatest practical extent any undesired

effects of a failure sequence.

If cable trays are used as mechanical support for experimental circuits, they should be solely

dedicated to this use and appropriately labeled. Any such use must be analyzed for detrimental

heating effects of the proposed configuration.

10.9.1.2.2 POWER SUPPLY INTERFACE BETWEEN UTILITY SYSTEMS AND R&D

EQUIPMENT

Utility supply voltages should be brought as near to the utilization equipment as possible using

NEC-compliant wiring methods.

Any temporary wiring methods used (e.g., extension cords) should be approved by the AHJ for

a specified limited time.

Flexible cords and cables should be routed in a manner to minimize tripping hazards.

The conventional use of cable trays is defined in NEC Article 392. If power cables are placed in

a cable tray used for control and signal cables, separation is advised but not always required.

According to NEC Article 392.6(E), multiconductor cables rated at 600 volts or less are

permitted to be installed in the same cable tray. This presumes the cables are listed, having a

minimum rating of 300 volts. However, cables rated over 600 volts require separation from

those rated at 600 volts or less, per Article 392.6(F). Communications cables are required to be

separated from light or power conductors by at least 2 inches, in accordance with NEC Article

800.52(A)(2).

Certain experimental configurations or physical constraints may require the unconventional

application of cable trays. Only the AHJ may approve these unconventional applications. If

deemed necessary, enhanced fire protection or other safety measures shall be used to ensure

safety to personnel and equipment.

For coaxial, heliax, and specialty cables used for experimental R&D equipment, where NEC

tray-rated cable types are not available which meet the technical requirements of the

installation, the non-tray-rated cables shall be permitted with the approval of the AHJ. If deemed

necessary, enhanced fire protection or other safety measures shall be used to ensure safety to

personnel and equipment.

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