On Sunday 23 March 2008, Justin Shore wrote: > There are a few things to remember. Code only permits you to load a > circuit to 80% of its maximum-rated capacity. The remaining 20% is the > safety margin required by the NEC. Knowing this that means that the > 12Kw specified above require 7x 20a 120v circuits or 5x 30a 120v circuits.
Cord connected loads can be 50A easily enough; something like a NEMA L21-60P can give you 18KW in one plug (after 80% derating); if you could use 277V the L22-60P is available to get you almost 40KW on one plug (again, after the 80% is factored in; it's almost 50KW at 100% rating). Hubbell makes 60 and 100A plugs and receptacles if 40KW isn't enough. PDU's for these are more scarce, but I'm sure Marway would build to suit. We have a few of the older Hubbell 50A twistloks here that were used for some sort of signal processing equipment back in the day. > Also remember that many of the larger servers (such as the Dell 6850s or > 6950s) are 240v and will require a pair of dedicated circuits (20a or 30a). The 6950 can run on 120VAC. That is one of the primary reasons we bought 6950's with Opterons instead of 6850's with Xeons; I only had 120VAC capable UPS's at the time. With router densities going way up, and heating going along with them, this facilities issue can even impact the network operator. > I would also recommend that you look into in-row power distribution > cabinets like the Liebert FDC. We have Liebert PPA's here. Two 125's and a 50. > Grounding is a topic that is worthy of its own book. Consult an > electrician used to working with data centers. Don't overlook this > critical thing. Ground reference grid. See Cisco's 'Building the Best Data Center for your Business' book and/or Sun's Blueprint series datacenter book for more good information. Also be thoroughly familiar with NEC Article 645. While this discussion might seem out of the ordinary for a network operator's group, it is a very good discussion. Another good resource for datacenter/commcenter information is www.datacenterknowledge.com; at least I've found it to be. -- Lamar Owen Chief Information Officer Pisgah Astronomical Research Institute 1 PARI Drive Rosman, NC 28772 (828)862-5554 www.pari.edu
