The emergency shutdown switch should be within arm's reach of the operator, be easily identifiable, deenergize all power to all equipment associated with the system, be separate from the routine on/ off switch, and be located to protect the employee from moving parts. However, the emergency shutdown switch should not disconnect auxiliary circuits necessary for safety (such as cooling).

9.7.3 SPECIAL CONSIDERATIONS

The disconnecting means should interrupt the source voltage for thyristor controlled equipment. Do not rely on disconnecting the control voltage.

9.8 MARKING AND LABELING REQUIREMENTS

9.8.1 GENERAL MARKING REQUIREMENTS

For all chassis and rack cabinets (electrical, computer, power distribution, etc.), the manufacturer's name, trademark, or other descriptive marking of the organization responsible for the product should be identified.

Other markings for power requirements are:

1. Voltage.

2. Maximum rated current in amperes. 3. Wattage.

4. Frequency (computer only).

5. Other ratings as specified in the NEC.

(See ANSUISA-S82.01-1988 Section 5.3.4 and NEC Section 110-21)

9.8.2 HAZARD MARKING REQUIREMENTS

All enclosures containing exposed energized circuits over 600 volts nominal should be marked "Danger High Voltage Keep Out" with a label that is permanent. These areas shall be accessible to authorized personnel only. The label shall be placed in a noticeable location on the access panel to the enclosure. Mark all other hazards that are associated with the equipment.

9.8.3 OTHER REQUIREMENTS

All equipment markings shall be of sufficient durability to withstand the environment involved and should be large enough to read.

To obtain the correct chassis load requirements for marking and labeling, monitor individual chassis while under load. Many chassis have components that are not energized except under certain conditions.

A normal current draw may be a few amperes, but when the chassis is sourcing current to a load, the current draw may be much higher. Individual loads, internal and external, may be tabulated and added to determine the chassis current labeling requirements.

For rack cabinets with power distribution units, the outside of the rack cabinet should be labeled with the input parameters of the power distribution system installed within it.

For rack cabinets without power distribution units the outside of the rack cabinet should be labeled with the total current on the combined systems installed within it.

Clear working space and headroom shall meet the NEC requirements (see Figs. 9-4 and 9-5). The clear working space and passageways to this space should not be used for storage. At least one 24 inch wide (minimum) passageway should be provided for travel to and from the clear working space.

While maintenance, repair or calibration are being performed, personnel should identify clear working spaces via suitable means such as "Danger" or "Caution" barrier tape, or barricades to keep other personnel from entering the clear working spaces. (See Section 2.9.)