Date: Sat, 15 Nov 1997 22:41:04 -0600 (CST) From: Chris Dillon <cdillon@tri-lakes.net> To: Dev Chanchani <dev@wopr.inetu.net> Cc: freebsd-isp@FreeBSD.ORG Subject: RE: Power Message-ID: <XFMail.971115225541.cdillon@tri-lakes.net> In-Reply-To: <Pine.BSF.3.95q.971115130536.14527A-100000@wopr.inetu.net>
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On 15-Nov-97 Dev Chanchani wrote: > >We had an extended power outage last night. After realizing that our >UPS's >would not keep our network up for the black-out, I ran to sears with a >credit card and bought a Craftsman generator. > >My lesson in power began :) > >I was wondering if anyone has been through this and could help me on a >couple of points: > >We have our servers, switches and routers plugged into APS UPS's (600's >and 650's). The UPS's are plugged into surge protectors. The surge >protectors are plugged into 15 AMP 12 guage 100 ft extension coards. We >ran the extension cords (took them out of the wall) and plugged them into >the generator. The 650 UPS could not take it, it was flipping between >generator power and UPS power every second. So... my questions are as >follows: Extension cords are usually not a good idea if high currents are being drawn. If they must be used, use very heavy-duty extension cords. 12 gauge might just barely be enough for that kind of distance. >1. Can you plug a UPS -> Surge protector -> generator >2. Are there any specifics I should look for when planning the power >setup >of new servers and racks. >3. How much output does a genarator need per server (as a rule of thumb)? >4. Was the UPS switching from internal power to external power because >the >generator power was fluctuating, not enough power, etc? If you have a multimiter, or even better an O-scope, or even better a power analyzer, plug it in and start watching at various points along the power line. The UPS probably would never try to switch back to line at all if the power isn't clean, so apparently it thought everything was hunky-dory. What probably happened is that when the UPS moved the load from the internal power source back to the mains, the generator couldn't keep up with the quick surge in current, causing output voltage to drop too far, causing the UPS to switch back to internal power.. Of course this would continue forever. One way I can think of doing this is to use a TRUE UPS (i.e. Online UPS), which aren't as picky about their input power, usually. Another way might be to get a much larger generator than is required (one that can take a sudden increase in load without dropping supply voltage). >If anyone has experience with this type of stuff, any help and >information >would be greatly appreciated. > >Thanks in advance! > >PS: To anyone who does not have experience in this, you might want to >take >a look, because its not fun to learn these things in total darkness in a >ice storm.. ;) Speaking of ice storms, its about that time of year. I think I need to go visit Sears and find a good generator to use here at home. :-) --- Chris Dillon --- cdillon@tri-lakes.net --- Powered by FreeBSD, the best operating system on the planet. ---- (http://www.freebsd.org)
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