Some questions for choosing an uninterruptible power supply (UPS) unit for a new workstation, questions that came up when I realized how ignorant I am about these things.

One thing I do understand is that a VA rating is not the same as the watts actually supplied. Up until now, I just assumed that 1000 VA was "plenty" and blithely went on my way. I now understand a UPS unit rated at 1000VA may actually carry only 500 to 700 watts which would not be enough for the new workstation I'm hurriedly assembling.

So, for a feeding a computer with a 910 watt Power Supply Unit (PSU), what Uninterruptible Power Supply (UPS) specs should I look for?

If my probable maximum load is 800 watts but my PSU is rated higher, should I match the UPS unit to the probable maximum load or to the PSU’s maximum rating? I found these calculator/charts for sizing a PSU, which I am thinking also may be useful for guesstimating the maximum load that a UPS might need to carry:
Power Supplies: How Much Power Do You Need? (http://www.pcpower.com/technology/power_usage/)
Power Supply Selector (http://www.pcpower.com/Power_Supply_Selector.html)
For me, it looks like I might have a maximum load of roughly 775-800 watts. I'm getting a PSU with some headroom. I suspect that ought to match the PSU and UPS, but I do not know.

How does Automatic Voltage Regulation (AVR) work? When running on line voltage (as opposed to batteries), is AVR limited in any way by the power rating for battery operation? Or does AVR basically work like a line conditioner and provide stable power to whatever is hooked up to it regardless of what the UPS unit might supply if it were on battery?

How tightly does AVR have to work to be safe with the newer generations of PSU and CPUs (such as the I7-3930k)? For instance, I have been using a Tripp-Lite G1000UB with the old system. We have dirty power here. Today, the line voltage from the tap was bouncing between 123 volts and 115 volts. (Obviously, I’m in the North America and we’re talking 60 Hz power). I put a VOM on a power-out cable from the Tripp Lite unit. The output from the UPS was hovering around 119.8, although slowly fluctuating as far down as 119.5 and up occasionally to 120.00. Checking specs for UPS units shows a lot of them listing output at “120 v +/- 5%.” That means the tolerance is 6 volts above or below 120 v, right? So, the AVR on my existing unit is working okay, right? The small variation between 119.5 v and 119.9 v is nothing to worry about, right?

Do I need “pure sine wave” output from my UPS if the PSU manufacturer does not spec it in the manual or on the web site? (PC Power & Cooling does not spec it for the 910 Watt unit I have purchased.)

Prices for UPS units rated up to 1000 watts are about half (or less) of the cost of units rated over that. If a power outage occurs while my workstation is, say, in the middle of a long session transcoding 1080 AVCHD to Blu-ray or DVD, I’m guessing that there will not be a full load. A big load, but not the max. The processor will be high but only some of the disks and the raid card will be pulling power. Is this a reasonable assumption or not? Or, with a 900 watt power supply, should I be looking at a UPS unit that carries, say, 1500 watts?

Also, given that price differential, should I plan on using a sub-1000 watt UPS unit exclusively for the workstation and not plug anything else into it? (For example, since I work with twin monitors, should I keep the present Tripp-Lite unit for feeding power to the monitors?)

I’ve assembled a preliminary list of possible candidates for purchase. Depending on what is said in reply to my questions, some of these will drop off the list. But for now, I will be grateful for comments from anybody who has experience with any of these units or who feels knowledgeable enough to help make a selection.

Tripp Lite SMART1500LCD Smart Pro Digital 1500 VA 900 Watts 8 Outlets Line Interactive UPS w/ LCD display
Newegg.com - Tripp Lite SMART1500LCD Smart Pro Digital 1500 VA 900 Watts 8 Outlets Line Interactive UPS w/ LCD display (http://www.newegg.com/Product/Product.aspx?Item=N82E16842111052)
$202

Tripp Lite OMNIVS1500 OMNI VS 1500 VA 940 Watts 8 Outlets Line Interactive Tower UPS
Newegg.com - Tripp Lite OMNIVS1500 OMNI VS 1500 VA 940 Watts 8 Outlets Line Interactive Tower UPS (http://www.newegg.com/Product/Product.aspx?Item=N82E16842111050)
$200

CyberPower CP1500PFCLCD UPS 1500VA / 900W PFC compatible Pure sine wave
Newegg.com - CyberPower CP1500PFCLCD UPS 1500VA / 900W PFC compatible Pure sine wave (http://www.newegg.com/Product/Product.aspx?Item=N82E16842102134)
$187

CyberPower Professional PP1500SWT2 1500VA 1000W 7 Outlets UPS
Newegg.com - CyberPower Professional PP1500SWT2 1500VA 1000W 7 Outlets UPS (http://www.newegg.com/Product/Product.aspx?Item=N82E16842102050)
$343

For a UPS which will support more than 1000 watts, I see that Steve Kalle has recommended this unit in some earlier postings:

CyberPower Professional PP2200SW 2200VA 1500W 6 NEMA 5-15R, 2 NEMA 5-20R Outlets UPS
Newegg.com - CyberPower/UPS (http://www.newegg.com/Store/BrandSubCategory.aspx?Brand=1821&SubCategory=72&name=CyberPower-UPS)
Currently sells for $472.

I am aware that this unit requires 20 amp NEMA plugs, but that is not a problem. My studio is already wired with a 12 guage cable fed from a 20 amp breaker. I can easily swap in another 20 amp NEMA outlet, if I were to buy this unit. I suppose that, if I bought this one, I could plug both monitors into it, too.

Anybody else have any experience with this unit?

Jay,

PSU:

The PSU is one of the most crucial components in any system but also the one component most often overlooked. A good PSU will give you years of reliable work on your PC, a suboptimal or mediocre PSU will give you tremendous headaches and unexplainable crashes, hangs or errors, causing you to miss deadlines.

Go to http://extreme.outervision.com/PSUEngine and get the Pro version. Enter all your components, including planned expansions, set the Motherboard to High End - Desktop, set the CPU Utilization (TDP) to 100%, set System Load to 100% and Capacitor Aging to 30% and press the Calculate button. Add 10 - 15% to this Wattage for safety and note the required amperage on the various rails (+3.3V, +5V and +12V). Based on these figures, select a good GOLD label PSU, that meets the total wattage and the amperage on each rail. It is your best guarantee for long and reliable, trouble-free editing.

This will also tell you what VA capacity a suggested UPS will need.

My personal favorite is the APC Smart-UPS 2200VA LCD 230V (http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SMT2200I&tab=models)

Hi, Jay...............

Hmm, where to begin.

UPS Max O/P Power, I guess.

As long as the UPS can supply the power required to run ALL attached equipment - processor box, external drives, screen & anything else that must keep running, you're good to go.

More is better, but matching your actual requirements is fine.

HOWEVER, what has not been mentioned is FOR HOW LONG!

If you scroll down to the bottom of Harm's post, and click on that last link he's given, and scroll down to the bottom of that, you'll find a fascinating graph of unit run time versus load.

Now, bear in mind, that UPS he's indicated weighs over 100 pounds, fercryingoutloud!

A 500 Watt load for 60 minutes! A 1000 Watt load for 30 minutes!

So, you need to ask yourself this question: "How long do I want this thing to keep me running?"

Enough time to take the system down gracefully, even though I'm going to lose this render? (5 minutes max).

Enough time to finish this render? (5 hours+, maybe).

If it's the first, as long as whatever you choose can hold it's breath for 5 minutes with your full system load on it, you're good.

If it's the latter, you're going to need a generator, not a UPS, else it'll be bigger (and a darn sight heaver) than your car.

Don't stress yourself too much about sine/ not sine, voltage fluctuations and all that stuff, modern power supplies can run on pretty much anything you throw at them.

The important question is "How much, for how long?"

Over to you.


CS

Re: Harm's comments:

By coincidence, there is an active thread on the Adobe forum here which highlights Harm's comments about the importance of selecting a sufficient PSU,

http://www.dvinfo.net/forum/adobe-creative-suite/504801-psu-issue-only-pp-cs5.html

By the way:
I hope nobody is confused by the similarlity of the abbreviations "UPS" and "PSU."


Re: Chris's comments:
Run time is a consideration. Long run-time would be great, but I will be content with having enough time to shut down gracefully even if it means losing a render. What I want to avoid is the hard drive corruption and/or Windows corruption that can result from abrupt power losses. My old 9xx workstation was speedy enough that I no longer had much need for unattended, overnight renders.


Notes on UPS units

I have not yet tried the caclculator link Harm provided. It has to be purchased --- minimal charge --- but I've been on the road where I know nothing about the security of the systems I am using and that makes me reluctant to make online purchases there.

I did check out Harm's UPS model. On the PPBM5 site, Harm's computer system is entitled: "Harm's Beast." He has a UPS to match! Since Harm's set-up is a regular disk farm, he definitely needs that 2000VA UPS!

My needs are more modest. Likely to be a bit more modest as it seems that the I7-3930k processors will not be shipping again for a couple of weeks. Because of the numbers of existing backorders that need filling, it probably would be longer time before I could get one. Looks like I'll have to choose something else in order to get a replacement workstation right away. (While the I7-3930K processors are in stock at reputable vendors, you can guess that I'm not going to spend $1100 ($US) to get one.)

Oopps. In the last sentence I was referring to 3960X as being in stock at $1100 ($US).