The Design and Organization of Data Centers/Electrical

Types of Service 120 V 1 phase Hot, Neutral, Ground 240 V 1 phase 2 Hots, 1 Ground 208 V 3 phase 3 Hots, 1 Neutral, 1 Ground 208 V 1 phase 2 Hots, 1 Ground 480 V 3 phase 3 Hots, 1 Neutral, 1 Ground 48 V DC Positive & Negative Uninteruptable Power Supplies Absolutely necessary Types Central UPS All equipment stays up for same length of time. Rack-mounted UPS Put batteries where they are needed most. Easy redundancy with dual power supply computers. Server-mounted battery Google servers are connected directly to the AC feed with no UPS in the middle. Instead, each server has its own 12 VDC battery, which is used to power the server during power outages."Google Unveils Custom Server/UPS/Power Supply" by Joe Polastre, April 1, 2009Slashdot: "Google Reveals "Secret" Server Designs" April 02, 2009 Brick UPS Good for smaller installations. Easy redundancy with dual power supply computers. Sizing Loads that cannot tolerate any outage shall be placed on UPS power. Critical systems, such as the air conditioning cannot tolerate a brief outage, so they should be supported from generator power. Battery run time for UPS loads are dependent upon the budget and level of reliability required. With a well designed backup generation system, UPS runtime may be minimized since the gensets will be online in 8 to 20 seconds. Power Interruption Plan for unattended shutdown and restart whenever possible. Consider remote alert of power interruption. Make sure the KVM is also on UPS. Make sure you have emergency lights and flashlights for working in the dark. Estimating remaining run time Restart of UPS after full drain Redundant UPS systems Rack-mounted - side to side redundancy. Central UPS - need two of them with separate breaker boxes/PDUs and color coded system. Generators Determine your local outage characteristics for your power supplier. Do they tend to be infrequent, but long? Common, but short? On-site vs delivery contract On site minimizes need for large UPSes Environmental issues and permit requirements for fuel storage Layout and Redundancy Look for computers with dual power supplies, or, less preferably, make sure you have redundant boxes per function. This allows for rearranging power cables and moving a box from one area to another without turning it off. Maintain side-to-side redundancy by placing power strips on separate breakers or UPSes. Remote Power Control Remote power on and off Resetting stuck machines and routers Power on sequencing Electrical Grounding/Earthing All metal server or network racks and cabinets, overhead raceways and metallic conduit must be properly grounded to each other and to ground.