HP XP20000/XP24000 HP StorageWorks XP24000/XP20000 Disk Array Site Preparation - Page 40
Frequency, Safety and dedicated ground, Grounding requirements, AC receptacle requirements
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Avoid the use of a line voltage conditioner. Make sure that a power distribution unit (if used) provides the correct voltage to support your entire system. Frequency Usually, AC line frequency is determined by your local power providers. In some cases, electrical power is supplied by generators. Shifts in AC line frequency can cause system errors. An HP representative can monitor the frequency of the input AC line power and make recommendations, if necessary. The HP system requires that the line frequency fall within these limits: 50 Hz ±3 Hz or 60 Hz ±2 Hz. Safety and dedicated ground The primary reason for earth grounding electrical systems is safety. The safety ground is required by the National Electric Code (USA) and most other local, regional, and national codes. In addition to safety ground, HP requires that a dedicated (earth reference) ground be installed as a common reference point for all system components. Consult with an HP representative and your electrician to ensure that your electrical system meets all local and national safety codes. Grounding requirements Your site's electrical subsystem must meet all of the following conditions: • Earth grounding as prescribed by your local country codes. • An insulated grounding conductor that is identical in size and insulation material and thickness to the ungrounded branch-circuit supply conductors. It should be green, with or without yellow stripes, and is to be installed as a part of the branch circuit that supplies the unit or system. This means the ground conductor must be run in the same conduit, armored cable, or other cable bundle as the phase wires. • The grounding conductor should be grounded to earth at the service equipment or other acceptable building earth ground such as the building frames (in case of a high-rise steel-frame structure). • IT-configured grounding systems are not certified for use with the HP system as these grounding systems may not have solidly conductor-connected grounded power systems and/or they may have resistive impedance inserted in ground and/or neutral lines. The HP system requires a solidly conductor-connected ground and may require a separate neutral in the case of WYE or STAR connections. For the HP system, TN grounding systems are preferred. AC receptacle requirements When receptacles are used to connect disk array components to AC power, they must include a dedicated ground connection that is insulated from the receptacle. It is important that the receptacle box be grounded with an additional ground connection that is separate from the dedicated ground. The additional ground can be hard conduit. CAUTION: When installing the receptacles, the electrician must ensure that each receptacle has its own neutral (if required) and ground. Using the same neutral/ground for more than one circuit causes voltage loss and heat problems and can create a fire hazard. A shared neutral conductor that fails open-circuit can cause over voltage damage to equipment. 40 Site requirements for the HP Disk Arrays
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