UPS and Powersupply question

[Jeff]

I just built a medium duty server in a tower case and still need to buy a
UPS/battery-backup for it. I'm not exactly certain how to determine how
large a unit I will need to power the thing for 20 minutes or so in the
event of a power failure. The PSU is 1000 watts, I'm running one dual-core
AMD processor (somewhere around 100 watts, I think - Opteron 2218) but I may
add a second processor, 4 15K SAS drives, 1 7200rpm Sata drive, adaptec
hardware raid controller PCIe, and of course 5 case fans. ...no monitor and
on-board video only. It's been awhile since I had classes in electricity,
and also I know that the drives draw most of their power on start-up, but
little at idle. So I'm not sure how to determine the rating required for
about 20 minutes. Can someone explain the math here? ...any recommendations
on a good-reliable UPS unit with replacement batteries that aren't hard to
find and reasonably priced? I've owned a 1000va APC unit for about 10 years
and 3 battery changes that has treated me well for a home machine, but I
don't know if some of the lesser priced units are as good. ...and I don't
know if the software for the automatic shutdown and monitoring for these
units works properly with W2003.

Jeff

 

[Paul]

I just built a medium duty server in a tower case and still need to buy
a UPS/battery-backup for it. I'm not exactly certain how to determine
how large a unit I will need to power the thing for 20 minutes or so in
the event of a power failure. The PSU is 1000 watts, I'm running one
dual-core AMD processor (somewhere around 100 watts, I think - Opteron
2218) but I may add a second processor, 4 15K SAS drives, 1 7200rpm Sata
drive, adaptec hardware raid controller PCIe, and of course 5 case fans.
...no monitor and on-board video only. It's been awhile since I had
classes in electricity, and also I know that the drives draw most of
their power on start-up, but little at idle. So I'm not sure how to
determine the rating required for about 20 minutes. Can someone explain
the math here? ...any recommendations on a good-reliable UPS unit with
replacement batteries that aren't hard to find and reasonably priced?
I've owned a 1000va APC unit for about 10 years and 3 battery changes
that has treated me well for a home machine, but I don't know if some of
the lesser priced units are as good. ...and I don't know if the software
for the automatic shutdown and monitoring for these units works properly
with W2003.

Jeff

The PCGuide site has some info. Your load is not the size of the
power supply, but is the sum total of the powers being drawn by
the computer components. So, your power would be 100W (processor)
+ 4*15W (disks) + 13W (sata) + ~50W (motherboard) and so on.
The 1000W power supply never draws 1000W exactly, and only draws
enough power to run the computer components. The inefficiency of
the power supply (the heat it kicks out), also has to be included
in the calculation, so there is a difference between a 68% efficient
ATX aupply and a new 80%+ efficient supply. The 80% efficient supply
means multiplying the computed internal power by 1.25x . You'll also
need to learn about VA, watts, and power factor. A power factor
corrected power supply would make this an easier exercise to understand,
as the power factor would be close to 1.0 .

http://www.pcguide.com/ref/power/ext/ups/func.htm

Runtime comes from a chart, but can also be worked out from
knowing the watt-hours stored in the battery (amp-hours * Vbattery).
The faster it is discharged, the less efficient the battery is at
returning the energy stored in it.

Paul

 

[Ed Medlin]

I just built a medium duty server in a tower case and still need to buy a
UPS/battery-backup for it. I'm not exactly certain how to determine how
large a unit I will need to power the thing for 20 minutes or so in the
event of a power failure. The PSU is 1000 watts, I'm running one dual-core
AMD processor (somewhere around 100 watts, I think - Opteron 2218) but I
may add a second processor, 4 15K SAS drives, 1 7200rpm Sata drive,
adaptec hardware raid controller PCIe, and of course 5 case fans. ...no
monitor and on-board video only. It's been awhile since I had classes in
electricity, and also I know that the drives draw most of their power on
start-up, but little at idle. So I'm not sure how to determine the rating
required for about 20 minutes. Can someone explain the math here? ...any
recommendations on a good-reliable UPS unit with replacement batteries
that aren't hard to find and reasonably priced? I've owned a 1000va APC
unit for about 10 years and 3 battery changes that has treated me well for
a home machine, but I don't know if some of the lesser priced units are as
good. ...and I don't know if the software for the automatic shutdown and
monitoring for these units works properly with W2003.

Jeff

I would think that an APC model 150 D (1500) would do the trick. It's price
is not bad either. I have one and it will keep me up and going 30 mins or
more. I have a 535w (peak) 450w PSU, 5 hdds, ATI X850 PCIE video, Hitachi
LCD monitor and all the other usual things like printer etc. The last time
we had a power outage I was in the middle of a print job and it surprizingly
kept me going until finished, about 20+ mins or so with aome power to spare.
It connects via USB and gives a power estimate in the tray much like a
laptop when it is on battery power.

Ed

 

[Timothy Daniels]

I've owned a 1000va APC unit for about 10 years
and 3 battery changes [.............]

That seems a bit too frequent. I've had a 500VA APC
UPS for 8 years, and it still works fine. I keep it constantly
on and in a well-ventilated place off the floor, so there is
very little temperature and charge cycling.

*TimDaniels*

 

[John Weiss]

I just built a medium duty server in a tower case and still need to buy a
UPS/battery-backup for it. I'm not exactly certain how to determine how
large a unit I will need to power the thing for 20 minutes or so in the
event of a power failure. The PSU is 1000 watts, I'm running one dual-core
AMD processor (somewhere around 100 watts, I think - Opteron 2218) but I
may add a second processor, 4 15K SAS drives, 1 7200rpm Sata drive,
adaptec hardware raid controller PCIe, and of course 5 case fans. ...no
monitor and on-board video only.

The main problem is that there is not enough data on most home-grade UPS
boxes to give you that information. The popular VA rating (e.g., 1500 VA in
an APC 1500ES) only tells you the maximum load it can sustain -- NOT how
long the battery will last supplying that load. IF all the HDs are powered
down, a typical 1500 VA UPS MIGHT run it for 20 minutes without a monitor.
However, with all the HDs and fans running, 5-10 minutes is probably a
better guess.

The itty-bitty battery in the typical UPS only has a 5 amp-hour (or so)
capacity at 12 volts. You need a UPS that will allow more batteries to be
attached. Then you might be able to get a marine grade deep-cycle gel-cell
(70+ amp-hours) and attach it to the system. However, you'd likely have to
disconnect that battery and recharge it with a higher-capacity charger after
it is run down...

 

[Jeff]

I've owned a 1000va APC unit for about 10 years and 3 battery changes
[.............]

That seems a bit too frequent. I've had a 500VA APC
UPS for 8 years, and it still works fine. I keep it constantly
on and in a well-ventilated place off the floor, so there is
very little temperature and charge cycling.

*TimDaniels*

...now that I think about it, I overstated those battery changes. I think
that it was 3 total sets. 1 original, and two changes. ...and the last one
was fairly recently. ...so the original and one replacement lasted for
nearly 10 years.

Jeff

 

[Jeff]

I would think that an APC model 150 D (1500) would do the trick. It's
price is not bad either. I have one and it will keep me up and going 30
mins or more. I have a 535w (peak) 450w PSU, 5 hdds, ATI X850 PCIE video,
Hitachi LCD monitor and all the other usual things like printer etc. The
last time we had a power outage I was in the middle of a print job and it
surprizingly kept me going until finished, about 20+ mins or so with aome
power to spare. It connects via USB and gives a power estimate in the tray
much like a laptop when it is on battery power.

Ed

That's the one that I was looking at. ...price around $450 or so. My APC
1000 has powered my old P3 dual processor with 4 drives and a 21 CRT monitor
through several minutes of a few different power outages - one involving a
fatal car crash outside my house that involved a car into the powerline. Our
latest involved a large transformer right at the power company that
completely blew up (one of only 4 supplying 3 entire counties). ...took
about 2 days to get the power back up. There's really nothing that would
have completely powered a machine through either of those outages - the
others have been very short duration - I've never bothered to time how long
the thing would keep the machine running. I've also never bothered to use
the connection to the computer to do the auto power down thing, but since
this server will be remotely operated, I guess that I'll have to install
that and see how it works.

Thanks for the info

Jeff