Date: Wed, 11 Aug 2010 14:25:57 -0500 From: Ryan Coleman <ryan.coleman@cwis.biz> To: Chuck Swiger <cswiger@mac.com> Cc: User Questions <freebsd-questions@freebsd.org> Subject: Re: UPS question Message-ID: <5304A319-0406-4510-B6B2-8FD609239FF9@cwis.biz> In-Reply-To: <3135A83C-6FD9-4C3B-958F-11EE85221061@mac.com> References: <E1B44814-1433-4FBE-902B-BCC1944FBFCD@cwis.biz> <3135A83C-6FD9-4C3B-958F-11EE85221061@mac.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Thanks, Chuck. I talked with a former colleague that has a lot of experience in specing = out UPS requirements (between battery-ready and generator-ready backups = at the office they have up to 5 minutes of battery backup before the gas = generator is needed with a 128-hour recharge time just to support their = servers and wiring racks in the office). He thinks that at 500W needed it would give me about 12 minutes on a = 1400VA. My consideration is, then, give the server 2 minutes on battery. = If full power has not been returned, shut down the server but leave the = modem (w/ wireless) and switch running with power for up to 6 hours. Now I need to build a server (looking at RAID5 8x2TB) for less than = $1600 w/o a CPU if I can... a local custom builder quoted me $4000 today = for a full system inc. CPU, RAM and DVD. -- Ryan On Aug 11, 2010, at 11:44 AM, Chuck Swiger wrote: > Hi, Ryan-- >=20 > On Aug 11, 2010, at 8:51 AM, Ryan Coleman wrote: >> Total: 495W >>=20 >> According to a calculator if I enter all that information: >> http://www.csgnetwork.com/upssizecalc.html >> It says that it will use 693VA. >=20 > That sounds reasonable. The better PSUs have "80 Plus" certification = for efficiency, and that's better than the typical wall warts used for = modems and switches and the like commonly manage. (The efficiency = they're assuming is a bit over 70%; using 80% would be around 600VA.) >=20 >> Enter that into http://www.csgnetwork.com/batterylifecalc.html >> It requires Amps... 495W / 120 voltage =3D 4.125 amps... doesn't = seem right but... >> 192 hours... that's not right, right? >=20 > Assume for discussion their number was right. In order to get 495W of = output load, the UPS needs to provide 693 volt-amps of juice to your = equipment. After the inverter and 10:1 stepup transformer used to = convert 12VDC or whatever the UPS batteries are charged to up to 120VAC, = the current needed would be 5.77 amps. However, the 12VDC battery = source itself would be getting a draw of 57 amps (ideally; again, the = inverter+transformer themselves might only rate about 90% efficiency for = very good quality UPS, so would be drawing more like 60 or 65 amps). >=20 > A standard APC/Tripplite/whatever 700VA UPS tend so have a lead-acid = battery reasonably similar to a car battery, and typically will have = around 100 amp-hours of charge; they'd probably give you 90 minutes of = backup time. But you can look up the detailed specs of specific models = and work from their amp-hour (or watt-hour) ratings-- actually, I think = I'm guestimating more from what a 1200VA unit might provide, and a 700VA = model is probably going to provide more like 40-60 minutes of power... >=20 > Regards, > --=20 > -Chuck >=20 > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to = "freebsd-questions-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?5304A319-0406-4510-B6B2-8FD609239FF9>