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Old 02-22-2010, 10:25 PM
Zitibake Zitibake is offline
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Join Date: Dec 2005
Posts: 113
Default genset capacity and datacenter standards

I have seen descriptions of the Tier-3 datacenters, as having power systems which are N+1, and sized to support "90% N" (versus 100% of "N" for Tier-2).

Does anyone know how to translate that for use with "failover" designs? For example, where one "catcher" UPS provides power to the bypass input of the primary UPS; or where there are cascading transfer switches, and a "swing" genset backs-up the primary genset?

I would guess that you still wouldn't exceed 90% of one UPS. But for the generator, would you want to stay below 90% of Standby load, Prime load, or Continuous load rating? Also, it seems like generators should be sized to handle the maximum load with allowable voltage drop, rather than some percentage of a rating; but I haven't seen this mentioned in datacenter tiers, or in TIA-942.
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