Enclosed Electrical/Electronic Equipment

DOE-HDBK-1092-98

9.0 ENCLOSED ELECTRICAL/ELECTRONIC EQUIPMENT

9.1 PURPOSE

This section provides guidelines to

1. complement existing electrical codes and recommend industry standards,

2. improve electrical safety in the work environment for personnel within the DOE complex.

3. eliminate the ambiguity and misunderstanding in design, construction and implementation

requirements for electrical/electronic equipment, and

4. assist the Authority Having Jurisdiction in providing information for acceptance of equipment

within the scope of this document.

9.2 SCOPE

This section addresses enclosed electrical/electronic equipment electrical safety guidelines which

are not specifically addressed elsewhere in the Electrical Safety Handbook.

These types of equipment include: instrumentation and test consoles; enclosed electrical/electronic

equipment; other laboratory diagnostic electrical/electronic equipment (stationary or mobile)

mounted in or on an enclosure or chassis; and special electrical/electronic equipment facility

requirements.

9.3 GROUNDING AND BONDING

Many ground system types exist within electrical equipment. All metal parts of electrical equipment

enclosures and chassis shall be bonded and grounded as per the NEC. The methods chosen to avoid

ground loops and reduce noise shall meet the requirements of the NEC (See Section 4).

9.3.1 OBJECTIONAL CURRENT OVER GROUNDING CONDUCTORS

Enclosed Electrical/Electronic equipment has both power and signal conductors entering and leaving

these enclosures. Objectional currents and noise may be the result of the design or installation of

conductors and equipment and their grounding locations. NEC Section 250-21 addresses these

objectional currents and noise (See Section 10.9.2.1).

NEC Section 250-21 must be used with care because it seems to give blanket authority to do whatever

is necessary to stop objectionable currents from flowing in the grounding system. This is not the

intent. This article specifically excludes modifying grounding systems in order to overcome noise

that may be causing problems in sensitive electronic equipment.

This NEC Section principally deals with objectionable currents that can flow over grounding

conductors due to severely unbalanced loads or improper installation practices. Because of the

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