UPS bogus ratings?

[Maverick2002]

So we have a few of these "2000VA/1200watt" Ultra UPS boxes at work, each one connected to 2x rack servers used for rendering. They don't last long at all during a power outage. Furthermore, one of them now keeps shutting down. Before purchasing a replacement, I want to make sure there's nothing fishy going on. It wasn't my purchase decision, but I can't find a single other "2000VA/1200watt" UPS that sells for $200. Cheapest ones I've found are:

Cheapest 2000VA/1200watt unit at Newegg (http://www.newegg.com/Product/...ult=True&Pagesize=100) = $400

Cheapest 2200VA/1500watt unit at TigerDirect, no 2000VA available (http://www.tigerdirect.com/app...c:234|&Sort=4&Recs=30) = $450

At Amazon (http://www.amazon.com/s/qid=12...2&rh=n%3A172282%2Cn%3A!493964%2Ck%3Aups+2000va&sort=price) = $515+

I did some research and came across a couple interesting white papers:

Understanding Power Factor, Crest Factor, and Surge Factor: http://www.apcmedia.com/salest.../SADE-5TNQYL_R0_EN.pdf
Watts and Volt-Amps: Powerful Confusion: http://www.apcmedia.com/salest.../SADE-5TNQYF_R0_EN.pdf

Here's one small excerpt:

"Power factor has an important implication in the specification of UPS run time on battery. Battery run time is
dictated by the watt load on the UPS. However, when many UPS manufacturers specify run time at full load
they are referring to full VA load, not the full watt load. For example, a UPS rated at 10,000 VA may be
rated for 20 minutes of run time at full load. In the fine print it notes that this full load is at a .65 power factor.
Therefore the load for the run time specification is really only 6500 Watts. The same UPS may have a 9000
W rating. This means that the run time was provided at 6500/9000 or 72% of the full load watt rating of the
UPS. At 72% of the Watt rating the UPS may run almost 70% longer than at the real full load Watt rating.
So this UPS which claimed to have 20 minutes of run time may only provide 12 minutes of run time at the
true full load Watt rating. To overcome this confusion, always make sure run time specifications are based
on Watt loads, and not VA loads."

I may be doing some real world testing with a power monitor on these, but before I spend the time, I also found this little random blurb on the net:

"the 2000VA/1200watt rating only describes the power inverter that converts the battery DC to 120 volt AC...

a 2000VA UPS doesn't necessarily last longer than a 1000VA UPS!

how long it lasts depends on how many Amp-Hours the internal battery can hold given the same usage. "

Is that accurate?

If so, are we (and everyone else) getting shafted on these "2000VA" UPS which are really no better than equally priced 1000VA APCs?

 

[Blain]

If you're looking for high quality, long lasting UPS...
Why are you filtering units out based on price?

If the UPS function is important for your rendering, cost should be secondary to clean power and battery uptime.

Are you looking for rackmount UPS?

 

[Maverick2002]

As I mentioned, this wasn't my decision. I recommended APC but the price didn't fly. Perhaps the powers that be will reconsider.

Rackmount UPS isn't really a requirement, but would be nice. We have them sitting on the floor right now. We could always just get a rack "shelf" and sit a couple units on it.

Really I'd like to know more about the ratings on UPS and how to determine a high/low quality one. I also wanted to know if this statement was accurate, and if so, I'd like to know more:

"the 2000VA/1200watt rating only describes the power inverter that converts the battery DC to 120 volt AC...

a 2000VA UPS doesn't necessarily last longer than a 1000VA UPS!

how long it lasts depends on how many Amp-Hours the internal battery can hold given the same usage. "

 

[Arcanedeath]

The statement how many amp - hours the battery has determines how long it lasts is correct, amp -hours is just a measure of the batteries capasity. I have an APC 1500XS unit and it has an optinal battery add on that can add much more runtime, but it still only a 1500VA UPS, so you need to purchase a UPS that have a high enough raiting to run everything that you are pluging into it (ie wattage or VA raiting) and it just so happens that most higher end and higher raiting UPS's tend to have bigger longer lasting batteries, but thats not always the case. you can have a tiny battery with a huge inverter which just means that you can power a ton of stuff, but only for a short period of time and it sounds like thats the case with your 2000VA Ultra UPS's, they have big inverters by low capasity batteries.

 

[ShawnD1]

Originally posted by: Arcanedeathyou can have a tiny battery with a huge inverter which just means that you can power a ton of stuff, but only for a short period of time and it sounds like thats the case with your 2000VA Ultra UPS's, they have big inverters by low capasity batteries.

And this isn't necessary a scam. Try to remember what the UPS is for. I've had my computer hooked to a UPS for the past 2 years and the records it keeps are telling the same story over and over again. A "power failure" where I live doesn't mean the entire house shuts down for 3 hours. A power failure means the power cut out for just 2 or 3 seconds. In a poorly wired building, another concern would be a 3 second undervoltage. Have you ever noticed the lights dim for a split second when your furnace fan or clothes dryer kicks on? That power fluctuation is what your UPS is stopping.

If you're looking for a real battery backup, get ready to open that wallet. Mine was about $100 and it only has enough charge to power my single computer for roughly 8 minutes; it's powering this with a standard car battery. If you're trying to power a rack server at 5kW, the battery for that will probably weigh several hundred pounds and cost several thousand dollars.

As Arcane stated, total charge is rated in amp-hours. The effective power of the UPS is still watts, and the VA rating means basically nothing if your computers have "active power factor correction" (most power supplies over $50 will have this).

If the UPS doesn't say the amp-hour rating, the next best indicator is size. While it is possible to get a lot of power in a small lithium battery, these are generally not used because they are very expensive (my cell phone battery was $60). Batteries used for backup power are most often the same as the lead-acid batteries in your car; they are big and extremely heavy. If you want it to power anything for more than a few minutes, it better be the size of a refrigerator or it's not going to work. Even the best UPS systems on Newegg are not intended for sustained use. For example: $5,000 8kw UPS is rated to last 4 minutes at full load.

 

[Stas]

You're better off with a gas generator, if it's crucial to continue rendering when the whole city is out of electricity and being evacuated due to a terrorist attack... But seriously, as ShawnD1 note, your UPS shouldn't need to last that long. I've had a UPS for the bast 2 years. The longest it ever had to power my system (according to logs) is 8 min. That's out of about 12 power outages. And undervoltage occurances have been way more popular with my UPS. Now, if the purchased UPS shuts down even though the load does not exceed specified limits, then you most likely have a faulty UPS, in which case, I suggest you contact the manufacturer.

 

[Maverick2002]

Thanks for the info - this explains why our "2000VA/1200watt" UPS is so cheap. It probably has the capacity of a 2 year old. I'll keep that in mind for future purposes. It doesn't have an amp-hour rating (http://www.tigerdirect.com/app...body=MAIN#detailspecs)

And it looks like one of the units is faulty. As far as rendering goes, we've been able to squeeze out ~5 minutes from each one of these with 2x 1U dual quad racks connected going 100% at full charge. Well, thanks for the info.

 

[Modelworks]

Easy way to explain it.
The rating of the UPS 2000VA just means what the inverter can handle power wise before it shuts off due to overload.
The run time is determined by the size of the batteries. Ampere hour ratings are not usually available on a ups without looking up the replacement batteries that it would use.
Some ups are designed for very long runtimes. One I had was a rack mount unit with jacks on the back for external batteries. As long as you could keep it with battery power it would run. Used it during a hurricane to run a tv and radio. It ran those for over 2 days with external batteries and could have run longer had the power not returned.

Most use 24VDC so they need two battery in serial. I used marine batteries that were rated for 135AH each x 4, so I had a 270AH supply.

 

[Maverick2002]

Ah, gotcha. Don't know why I hadn't though of this before. A bit misleading though if you don't do your research - you think a "2000VA/1200watt" unit will power say a 600watt system longer than a "1500VA/1000watt" unit, when it could be the other way around depending on the battery size.