Power source

These guidelines help to ensure that your data center has a quality power source.

The primary power source is normally a Wye-type or Delta-type, three-phase service coming from a service entrance or a separately derived source with appropriate overcurrent protection and suitable ground (service entrance or building ground). A three-phase, five-wire power distribution system should be provided for flexibility in your data processing installation. However, depending on the type of equipment installed, a single-phase distribution system might be sufficient. The five wire system enables you to provide power for three-phase line-to-line, single phase line-to-line, and single phase line-to- Neutral. The five wires consist of three phase conductors, one neutral conductor, and one insulated equipment grounding conductor (green, or green with yellow trace).

Conduit must not be used as the only grounding means.

Power panel feeders

Ensure that the feeder wires to the branch-circuit distribution panel (shown in Power quality) are large enough to handle the total server power load. It is recommended that these feeders service no other loads.

Branch circuits

The computer branch circuit panel should be in an unobstructed, well-lighted area in the computer room.

The individual branch circuits on the panel should be protected by suitable circuit breakers properly rated according to manufacturer specifications and applicable codes. Each circuit breaker should be labeled to identify the branch circuit it is controlling. The receptacle should also be labeled.

Where a branch circuit and receptacle are installed to service your server, it is recommended that the grounding conductor of the branch circuit be insulated and equal in size to the phase conductors. The grounding conductor is an insulated, dedicated-equipment-grounding conductor, not the neutral.

Branch circuit receptacles installed under a raised floor should be within 0.9 m (3 ft) of the server that they supply power to. If the branch circuits are contained in a metallic conduit, either rigid or nonrigid, the conduit system should be grounded. This is accomplished by bonding the conduit to the power distribution panel, which in turn, is tied to the building or transformer ground.

Phase rotation

The three-phase power receptacles for some equipment, such as printers, must be wired for correct phase rotation. When looking at the face of the receptacle and counting clockwise from the ground pin, the sequence is phase 1, phase 2, and phase 3.

Emergency power control

A disconnecting means should be provided to disconnect the power from all electronic equipment in the computer room. This disconnecting means should be controlled from locations readily accessible to the operator at the principal exit doors. A similar disconnecting means to disconnect the air conditioning system serving this area should be available. Consult the local and national codes to determine the requirements for your installation. National Electric Code (NFPA 70) article 645 provides the requirements for this room EPO.

Convenience outlets

A suitable number of convenience outlets should be installed in the computer room and the Service Representative area for use by building maintenance personnel and service representatives. Convenience outlets should be on the lighting or other building circuits, not on the computer power panel or feeder. Under no circumstances are the service convenience outlets on your servers to be used for any purpose other than normal servicing.