About UPS

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Ricky Romaya

Would a 600VA UPS supports a 500W PC power supply plus a 17" monitor? What
is the guidelines in choosing UPS' VA in relation to PC power supply
wattage plus monitor?

TIA
 
Would a 600VA UPS supports a 500W PC power supply plus a 17" monitor? What
is the guidelines in choosing UPS' VA in relation to PC power supply
wattage plus monitor?

TIA
Click to expand...

Consider actual power usage. 500W power supply speaks
nothing of how much power system uses. 17" monitor doesn't
consider whether it's CRT.

Determine the current needed to maintain system running,
then factor for how long you need it to run.

"In general" a 600VA UPS is sufficient for a single PC plus
17" monitor, but most PCs don't use 500W power supply.
 
Would a 600VA UPS supports a 500W PC power supply plus a 17" monitor? What
is the guidelines in choosing UPS' VA in relation to PC power supply
wattage plus monitor?

TIA
Click to expand...


Go to APC.com; they have a rudimentary UPS calculator on the site.
My experience says yes, it will for about 7-11 minutes which is more
than enough time to shut down safely.
 
Would a 600VA UPS supports a 500W PC power supply plus a 17" monitor?
Click to expand...

Sure. The only question is how long? Surely at least a few seconds. :)

I have a AMD 3500+ CPU with 1GB memory and 3 hard drives with 380 watt Antec
PSU. Plus 19 inch LCD monitor and also maybe 20 watts of fax machine and
network hub and router powered by UPS. An APC SU700NET UPS says this load is
40% of its 700VA rating. My batteries are old, but its calibration test keeps
it up 9 minutes before UPS shutdown. I think new batteries may help, but I
configure it as 2 minutes plus shutdown, to be certain it is usable.

Older AMD 1.1GHz CPU, 640MB, 2 drives, with 19 inch CRT monitor (and same
external load) was 5 minutes (instead of 9 minutes). Same UPS says this load
was 56% of its 700VA. The UPS was less usable with it, really wasnt enough to
do more than an immediate shutdown.

I really dont think the computer difference was much of a factor.
But an LCD display is like 40 watts instead of 120 watts for a CRT.
 
Consider actual power usage. 500W power supply speaks
nothing of how much power system uses. 17" monitor doesn't
consider whether it's CRT.
Click to expand...

That depends on whether the power supply is well-suited to the
system.

Seems to me that using the power supply wattage and monitor wattage
would be good indicators.

I would like to know what is the power rating for backup battery
supplies? Let's say the UPS will run a given system for 15 minutes.
How can I tell whether the same UPS will run a much more powerful
system for any time at all? What is the specification that indicates
maximum power flow from the UPS? Is it the volt/amp rating?

I'd like to be able to compare UPS models by maximum power output,
not necessarily battery size.

Partly curious.
 
Wayne said:
Sure. The only question is how long? Surely at least a few seconds. :)

I have a AMD 3500+ CPU with 1GB memory and 3 hard drives with 380 watt Antec
PSU. Plus 19 inch LCD monitor and also maybe 20 watts of fax machine and
network hub and router powered by UPS. An APC SU700NET UPS says this load is
40% of its 700VA rating. My batteries are old, but its calibration test keeps
it up 9 minutes before UPS shutdown. I think new batteries may help, but I
configure it as 2 minutes plus shutdown, to be certain it is usable.

Older AMD 1.1GHz CPU, 640MB, 2 drives, with 19 inch CRT monitor (and same
external load) was 5 minutes (instead of 9 minutes). Same UPS says this load
was 56% of its 700VA. The UPS was less usable with it, really wasnt enough to
do more than an immediate shutdown.

I really dont think the computer difference was much of a factor.
But an LCD display is like 40 watts instead of 120 watts for a CRT.
Click to expand...
May be some batteries that hold a larger number of Amp Hours that will
last a little longer. More powerful batteries are really the most
expensive part. There may also be some UPS systems that can signal the
PC so it knows to shutdown. Tube monitors probably pull more watts than
a PC. A PC with one large hard drive may last longer than one with 2
smaller hard drives. Fewer Drives means longer life.
 
Ricky said:
Would a 600VA UPS supports a 500W PC power supply plus a 17" monitor? What
is the guidelines in choosing UPS' VA in relation to PC power supply
wattage plus monitor?

TIA
Click to expand...

Power supplies are about 2/3 efficient nowadays, so when your power
supply is putting out 500W (the max for your PS apparently), it is
consuming about 750W. Not many computers need 500W though. As
suggested by other replies, add up the power requirements (in watts) of
the individual components of your system. Then multiply by 3/2 to
determine your minimum UPS rating. Unless I am wrong, volt-amps (VA)
are in this context equivalent to watts (W).
 
I really dont think the computer difference was much of a factor.
But an LCD display is like 40 watts instead of 120 watts for a CRT.
Click to expand...

Agreed. I am in the market for a UPS after a recent outage that
scrambled my OS partition, and I've learned I can get a smaller UPS
unit simply because I run an LCD instead of a CRT.

I also have one of those "Eliminator" style portable inverter/battery
units...if all is dead but the phone line, I can fire up the entire
rig, DSL and accessories for a couple of hours.

I actually bought it for the sailboat, but ain't technology grand.

R.
 
Ricky said:
Would a 600VA UPS supports a 500W PC power supply plus a 17" monitor? What
is the guidelines in choosing UPS' VA in relation to PC power supply
wattage plus monitor?

TIA
Click to expand...

My APC 650VA UPS supports my two PCs (380W and 300W) and 19inch CRT
monitor as well as two routers and an ADSL modem. During the last power
outage I was able to shut down all of these components without rushing
before turning off the UPS until power was restored.

Ari

--
spammage trappage: replace fishies_ with yahoo

I'm going to die rather sooner than I'd like. I tried to protect my
neighbours from crime, and became the victim of it. Complications in
hospital following this resulted in a serious illness. I now need a bone
marrow transplant. Many people around the world are waiting for a marrow
transplant, too. Please volunteer to be a marrow donor:
http://www.abmdr.org.au/
http://www.marrow.org/
 
Ricky Romaya said:
Would a 600VA UPS supports a 500W PC power supply plus a 17" monitor? What
is the guidelines in choosing UPS' VA in relation to PC power supply
wattage plus monitor?

TIA
Click to expand...

As other have said, this mostly depends on how long you'd like to keep
things running before the UPS gives out.

What I'd keep in mind is that APC units are pretty rugged, so buying a
used one and getting something bigger for less money is a good option.
Also, the Smart-UPS product line has significantly better features than
the standard consumer-grade Back-UPS, particularly the in-line power
conditioning in lieu of the stand-by method used by the latter. Check
http://www.apc.com/products/category.cfm?id=13 for details.

I got lucky and managed to find a Smart-UPS 1400-NET for just $165 at a
local used computer store. This unit retailed for $700 at the time.
Also, batteries (which will fail after 2-3 years) can be 3x cheaper
(brand new) on ebay than standard retail prices.
 
Determine the current needed to maintain system running,
then factor for how long you need it to run.
Click to expand...
Well, at 1st I wanted to ask how to calculate the total power needed for
my system, but after searching the web, I got some good pointers. I
listed below in case anybody interested.

Calculating power requirements
http://www.pcworld.com/resource/printable/article/0,aid,119585,00.asp

Power Supply Calculator
http://www.jscustompcs.com/power_supply/

Now, after using the power calculator listed above, I have an OT question
to this thread, what is the difference between willamete, northwood,
presscott, or other, in Intel P4 processors product line? How can I tell
which one I got?
 
Unless I am wrong, volt-amps (VA) are in this context equivalent to watts (W).

Not re sizing UPS.

This is a 500W PSU & 17" monitor:
o Typical PC = 85-170W, RAID SCSI Server = 300W
---- thus the 500W sizing is as much re safety/startup factor
---- for a PSU to supply 300W @ 60% efficiency it draws 500W
o A typical 17" CRT draws about 65-95W
---- a TFT draws around half that - mainly the backlight

So you have potentially a 300-600W load.

A 600VA UPS is aimed at 480-520W - the issue is not just the actual
runtime re battery sizing, but the actual invertor/transformer sizing.

So if the machine really is a heavily loader server, I'd aim for 600-1000VA.
If the machine is a home setup, few HD (not 7 SCSI RAID) 600-700VA.

You can fit larger batteries to UPS to gain runtime
o Either internally - some ship with a small size, eg, twin 11Ah
---- so you can upgrade to a larger size, eg, twin 17Ah
o Externally - the charging circuit will accommodate
---- so runtime is extended

However, in so doing you are not increasing the VA capability of
the UPS - that remains as per its rating. Most UPS (eg, APC) have a
thermal push-button circuit breaker on the rear, however size re VA.

So you do not always need to buy a super-big UPS to get a longer
run-time, but you do if you want to plug a lot of devices into it.

Rewireable IEC plugs can be used to provide UPS capability to the
usual "wall-wart" devices - eg, ADSL/56K modems, cordless phone.

APC are pretty good, there are other makes. If you need to replace
batteries try 1) burglar alarm suppliers for the smaller ones (7Ah),
or 2) fire alarm suppliers for the larger ones (eg, 11-17Ah+).

UPS runtimes are not particularly linear with load - a highly loaded
small UPS will have a very short runtime compared to a big one. So
sizing needs to consider the likely usage, if you simply need UPS
to allow a shutdown that is v.different from requiring 30min uptime.
 
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