Power Switches and Interlock Devices Specific Requirements

DOE-HDBK-1092-98

9.4.3 POWER SWITCHES AND INTERLOCK DEVICES SPECIFIC

REQUIREMENTS

For all electrical/electronic enclosures utilizing power switches or interlocks, the following should

apply:

1. Interlocks should be utilized where exposed voltages (50 volts or greater) are present in

equipment and access to the exposed live parts is not controlled (See Section 9.6.4).

2. Ensure all line side unprotected contacts are guarded on interlocking contactors or other

switching equipment.

3. Be suitable for the conditions, use, and location.

4. Circuit breakers used for the equipment power switch will be rated for switching under load.

5. Provide provisions for Lockout/Tagout requirements.

9.5 CHASSIS POWER DISTRIBUTION

Manufacturers are responsible for determining the safety of such chassis and/or enclosures and for

providing documentation showing how that determination was made. Unlisted commercial

equipment and in-house fabricated equipment shall be approved by the local Authority Having

Jurisdiction.

9.5.1 AC POWER DISTRIBUTION

9.5.1.1 CHASSIS BONDING AND GROUNDING

Metal chassis shall be effectively bonded to a main grounding point in the rack cabinet where

necessary to assure electrical continuity and shall have the capacity to conduct safely any fault

current likely to be imposed on it. (NEC Section 250-75)

In a chassis with ac service connected to it, the grounding terminal of its receptacle shall be internally

bonded to the chassis frame. (NEC Section 250-74)

If solder is used, the connection of the equipment grounding conductor shall not depend on solder

alone. (ANSI/ISA-S82.01-1988 - Section 9.5.4.4 and NEC Section 250-115)

The leakage current of cord connected equipment should not be more than specified in Subclause

9.11 of ANSI/ISA-S82.01-1988.

9.5.1.2 CONNECTIONS, CONNECTORS, AND COUPLINGS

Input/output ac power connections to the chassis shall comply with NEC requirements.

The exposed, noncurrent carrying, metal parts of panel mount connectors operating at 50 volts or

greater shall be bonded to the chassis.

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