Special Considerations - hdbk10920180

DOE-HDBK-1092-98

2) When the enclosure contains more than one bay, bond all grounding or bonding busses together.

3) All mounted chassis within rack cabinets shall have a grounding or bonding conductor attached

to the common grounding or bonding bus when the chassis is not grounded or bonded through

the power cord.

4) The grounding or bonding conductor shall be permanent and continuous.

5) Subassemblies mounted in other types of enclosures should be bonded by adequate preparation

of the mounting surfaces or by the use of a bonding conductor.

6) To provide protection against grounding or bonding conductor breakage, conductors between the

common grounding or bonding bus and moveable chassis should be braided cable or stranded

wire.

All grounding or bonding points should be tight for good continuity, identified by green color,

permanently labeled, and properly prepared by cleaning metal surfaces to bare metal or by the use

of serrated bushings. Anodized aluminum must be cleaned to bare metal.

The resistance across the bonding point should not be more than 0.1 ohm. If a measurement is

required, the method of measurement is to be determined by the user. (See ANSI/ISA - S82.01 - 1988

- Section 9.5.2)

9.3.4 SPECIAL CONSIDERATIONS

Systems feeding power isolation transformers must continue the equipment grounding conductor to

the equipment or the ungrounded equipment must be guarded and labeled.

For two-wire cord connected equipment, an equipment grounding connector should be installed

according to the manufacturer's instructions.

9.4 RACK POWER DISTRIBUTION

The following guidelines will provide the necessary information to correctly install power distribution

equipment within instrumentation racks containing electrical and electronic equipment.

9.4.1 GENERAL REQUIREMENTS APPLYING TO ALL AC POWER

EQUIPMENT WITHIN OR ATTACHED TO INSTRUMENT RACKS

9.4.1.1 LOADS

Knowledge of the loads that will be connected within a rack cabinet is necessary before starting

design of a rack power distribution system. All components must be sized correctly for the loads and

should provide for expansion.

Equipment enclosures may or may not contain a power distribution unit. A rack power distribution

unit contains a main overcurrent protection device and multiple branch circuits that are individually

protected against overcurrent. Without a power distribution unit, the power wiring is considered part

of one branch circuit.

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