OT: New PC!

Baron Munchausen · #1 January 11th, 2006, 10:14 PM

420 VA looks kinda scrawny for the machine you are building. The VA (volt amps) rating is supposed to be greater than the power draw of your system. If not, it will simply overload and shut down when the power fails. You'll get a slightly noisier crash than if you had no UPS.

If you are using an LCD instead of a CRT monitor that helps, but a 680 watt power supply demands a similar VA rating. 'Volt amps' are basically equivalent to watts, so you want at least a 680 VA UPS. A 750 is probably a good idea.

Hey, I'm using an 850 VA UPS to run a computer with an 'average' 250 watt power supply and a 19" CRT monitor (it draws a maximum of about 240 watts). Yes, it's much more than 'absolutely necessary'. That just means it lasts longer when the power goes out.

Yes, it's more expensive than the cheapest solution, but you definitely get what you pay for in backup battery power. You might want to go for a 1000 VA UPS -- 1 kw!

Will · #2 January 12th, 2006, 02:07 AM

If you go to a site like NewEgg, they will tell you the VA rating, and the wattage it is designed for. I have an APC BE725BB, which is a 725VA, 450W UPS (I have a 450W PSU). It came with a little monitor utility that lets you set timers when on the backup, so you can have your computer automatically shut down after some time, or hibernate.

Plus, you can use it for general purpose stuff. During the big blackout in LA this fall, I took it down to the lobby, and plugged the radio we have down there into it to figure out what happened (some dude from PG&E cut a wire he wasn't supposed to, and the entire basin got its power cut).

Baron Munchausen · #3 January 12th, 2006, 12:04 PM

Quote:

Will said:
If you go to a site like NewEgg, they will tell you the VA rating, and the wattage it is designed for. I have an APC BE725BB, which is a 725VA, 450W UPS (I have a 450W PSU). It came with a little monitor utility that lets you set timers when on the backup, so you can have your computer automatically shut down after some time, or hibernate.

Plus, you can use it for general purpose stuff. During the big blackout in LA this fall, I took it down to the lobby, and plugged the radio we have down there into it to figure out what happened (some dude from PG&E cut a wire he wasn't supposed to, and the entire basin got its power cut).

According to references I have, a 'volt-ampere' is one volt at one amp, and so equivalent to one watt. Therefore, the VA rating should be exactly the same as the wattage it can support. I wonder what they are really describing if they don't rate the VA and watts as the same?

AgentZero · #4 January 12th, 2006, 02:06 PM

Well, this one CyberPower Office Tower 750VA UPS Line Interactive RS-232 seems to be the most affordable UPS that could handle my 680W PSU. I don't know much about CyberPower, does anyone know what sort of name they have?

Fyron · #5 January 12th, 2006, 03:15 PM

Quote:

UPS�s are given volt-amp (VA) ratings, which is the maximum apparent power the unit can deliver to the load. UPS�s may also have a wattage (W) rating, which is not the same as the VA rating, and refers to the actual power consumption of your connected equipment.

From bottom of:

http://www.cyberpowersystems.com/electricity.asp

The "VA" rating is not what you need to be so concerned with, but rather the direct wattage rating. VA is more concerned with charge capacity (in a roundabout way), whereas W measure is maximum instantaneous power draw from the battery. Of course, higher VA means longer operation after power loss. VA vs. W ratings are used in this way very commonly for electric devices.

Cyber Power's site lists all the information for their UPSes, unlike that store site AZ linked to.

Baron Munchausen · #6 January 12th, 2006, 05:11 PM

Ouch...

http://www.apcmedia.com/salestools/S...NQYF_R0_EN.pdf

It looks like the actual wattage is closer to 60 percent of the VA. That means my 850 VA UPS is only 'adequate' for my load, and AgentZero is in fact going to need a 1000 VA or larger UPS!

AgentZero · #7 January 13th, 2006, 08:37 AM

Good grief. A 1000VA UPS starts at close to eur400. Now, correct me if I'm wrong, but it seems to me that the whole VA-Watts thing is basically a matter of how long the unit can last in the event of power loss, right? Or does it affect something else as well?
In the seven years I've been living in Dublin, there's only been one blackout I know of, but it was localized and didn't affect me. So I'm not too worries about blackouts, so much as power surges and the like. Given that, I'm wondering if I'd be better off buying just a surge protector, since the likliehood of a blackout is very low.