How to choose UPS size?

[wpcoe]

Please help me understand how a UPS works, which will hopefully help me choose one.

I live in rural Thailand, and power “flips” are common: it’s not uncommon for the power to flip off/on a couple times a week. Those “flips” are only about a second or two, but enough to turn off the computer. While, so far, I’ve always been able to reboot back into Windows, I know this cannot be a Good Thing and want a UPS.

Does a UPS merely act as a pass-through conduit for electricity when the battery is not called into service?

I’m using numbers out of thin air here, but say my computer typically runs at 250w, but when booting up draws 450w. Would I need a UPS that can handle 450w, or would one rated at 300w be enough to just keep my computer running during a power snap?

What I’m not clear on is if a UPS is “active” or “passive” during normal usage. Would repeatedly booting up on power line electricity using 450w be okay on a 300w UPS? Or, does the UPS need to be rated at the highest power draw of the computer?

I’m not too concerned about being able to boot off the UPS, I’m mainly interested in riding out the power snaps, and being able to properly shut the computer down from Windows in the less frequent (once every few months?) event of a true power outage.

My current computer specs are in my signature. I plan to upgrade when Ivy Bridge CPUs are released, and use onboard graphics on an i5 or i3 CPU, so my power requirements should be lower in the future with no graphics card, and lower TDP CPU, right? (I might remove the 500GB HDD, as well.)

 

[pandemonium]

Does a UPS merely act as a pass-through conduit for electricity when the battery is not called into service?

Yes, usually with much higher durability for surge protection as well (joule rating).

What I’m not clear on is if a UPS is “active” or “passive” during normal usage.

It's basically just a battery back-up. During normal usage the UPS is passive, minus surge protection, though a lot will have voltage regulation.

Would repeatedly booting up on power line electricity using 450w be okay on a 300w UPS? Or, does the UPS need to be rated at the highest power draw of the computer?

Read this article.

My current computer specs are in my signature. I plan to upgrade when Ivy Bridge CPUs are released, and use onboard graphics on an i5 or i3 CPU, so my power requirements should be lower in the future with no graphics card, and lower TDP CPU, right? (I might remove the 500GB HDD, as well.)

Best thing to do is to get a Kill-o-watt (watt reader), plug everything that you want to be uninterrupted, and get an actual reading while your computer is running at full load and all devices plugged in are in use, add 15% and that's your Watt requirements (you may want to consider lighting, monitor, printer, fax, speaker power, etc...). Watt readers are pretty inexpensive and useful. If you really don't have an option for that or care to bother with it, then just estimate 25% over your total TDPs and that should be plenty. Overloading the UPS can hurt, but having more than what you need can't.

 

[bononos]

A UPS is not necessarily just a pass through device. There are online UPS which are 'always on'.

The standby types will kick in during surges and outages, and line-interactive types will also kick in during brownouts and filter out noise. There are overlap btwn diff types I think. The important thing is to make sure that the holdup time of the psu > switching time of the UPS(typically in ms). Online and _possibly_ line interactive types do not have switching times (effectively 0ms).

The VA rating needed should be whatever your pc consumes + monitor (otherwise your monitor will be off during an outage and you'll find it hard to perform a graceful shutdown), your other components like speakers/printer don't need to be plugged on the UPS unless you want them to.

From your question, yes its the highest power draw (in case you were doing something intensive during an outage) of your pc. The VA rating of ups assumes unity power factor so in in the worse case you'll only need to overspec by 20% from your psu rating because you have an 80+ psu and you have an lcd which doesn't take much power. But practically speaking your system+ monitor won't take anywhere close to your psu max of 650W and your guess of 450W is already abit higher.

So just grab something around the rating of your psu or higher say 650-800VA(depending on what other components you want to be on the UPS) and the battery life should be in the specs, 5-10minutes or more depending on how long it takes you to shutdown in an outage situation. Killawatt meter is just too much hassle and unnecessary for choosing a UPS for a small home user.

If your power is noisy with transient dips/spikes you might want a online ups which will cost more in whcih case you'd better check on the quality of the output waveform.

 

[Charlie98]

Best thing to do is to get a Kill-o-watt (watt reader), plug everything that you want to be uninterrupted, and get an actual reading while your computer is running at full load and all devices plugged in are in use, multiply by 15% and that's your Watt requirements (you may want to consider lighting, monitor, printer, fax, speaker power, etc...).

You mean add 15%, or multiply by 115% ? Not nitpicking, just want to be clear... I'm in the same boat... time to retire the old 300w APC.

What about the Pure Sine models... are they worth it? As an example:

http://www.newegg.com/Product/Produc...82E16842102132

 

[wpcoe]

Read this article.

Thanks. I had wondered if VA = W.

Watt readers are pretty inexpensive and useful. If you really don't have an option for that or care to bother with it, then just estimate 25% over your total TDPs and that should be plenty.

It's not that I don't care or can't be bothered, I don't have a clue how to ask for a "watt meter" in Thai, and probably would need to trek into Bangkok to find one. It actually sounds like a "neat" device to have around. I'm curious by nature and could have fun testing things.

A UPS is not necessarily just a pass through device. There are online UPS which are 'always on'.

The standby types will kick in during surges and outages, and line-interactive types will also kick in during brownouts and filter out noise. There are overlap btwn diff types I think. The important thing is to make sure that the holdup time of the psu > switching time of the UPS(typically in ms). Online and _possibly_ line interactive types do not have switching times (effectively 0ms).

I hadn't considered brownouts, of which there are also plenty. Wish me luck trying to figure out which UPS's are line-interactive. I think one store sells APC brand, so I can jot down model numbers and Google them at home. For the Thai brands I need to see if their web sites are in English.

Whats the difference between online and line-interactive?

The VA rating needed should be whatever your pc consumes + monitor (otherwise your monitor will be off during an outage and you'll find it hard to perform a graceful shutdown), your other components like speakers/printer don't need to be plugged on the UPS unless you want them to.

From your question, yes its the highest power draw (in case you were doing something intensive during an outage) of your pc. The VA rating of ups assumes unity power factor so in in the worse case you'll only need to overspec by 20% from your psu rating because you have an 80+ psu and you have an lcd which doesn't take much power. But practically speaking your system+ monitor won't take anywhere close to your psu max of 650W and your guess of 450W is already abit higher.

Ah, that makes sense. I've assumed the highest load would be during boot, but what's to say that the power wouldn't "snap" during boot? Another thing I hadn't considered.

So just grab something around the rating of your psu or higher say 650-800VA(depending on what other components you want to be on the UPS) and the battery life should be in the specs, 5-10minutes or more depending on how long it takes you to shutdown in an outage situation. Killawatt meter is just too much hassle and unnecessary for choosing a UPS for a small home user.

If your power is noisy with transient dips/spikes you might want a online ups which will cost more in whcih case you'd better check on the quality of the output waveform.

Thanks for the advise. As usual, in addition to answering my questions, you've brought up issues I hadn't factored in.

 

[wpcoe]

I did some online shopping and found this page for a Thai UPS product line.

Why is a 1000VA unit only 400W? And, a 800VA unit is 300W?

(The ECO1000VA is ~US$80 and the ECO800VA is ~US$50.)

The APC models I see listed for sale jump from a 650VA/390Watt unit for ~US$105 and a 650VA/400Watt unit for ~US$115, to a 1100VA/660 Watt unit for ~US$180.

From what I gleaned above, the 650VA/390W APC unit should be big enough, right?

Reading the product info for the APC models, I see nothing about "line interactive," so they are "just a battery"? But, the cheaper Thai EMPOW brand is line interactive?

 

[bigsnyder]

I bought a refurbished APC SmartUPS 1000. I have never gauged my system with a watt meter, but my system is has follows:

Q9550 @ 3.7GHz
Gigabyte EX38-DS4 w/8GB ram
2x HD4850 crossfired
2x WD 640GB Black in RAID 0
250GB Seagate
X-Fi Platinum Sound Card
PCP&C 750W Silencer

The only other component plugged in the UPS is a 24" LCD monitor. UPS works great, never a problem. However, I never try to run system during a power outage. I stop what I am doing save everything and shutdown. Nice thing about this particular UPS is that it has a Load Meter on the front. Normal everyday tasks only pushes two out of five LEDs. Used a lower end APC 600VA a while without any problems until the battery went bad. The numbers and ratings are important, but generally the quality of the unit and condition of the battery will be a more determining factor.

 

[wpcoe]

Why did you go up to a 1000VA UPS if the 600VA was adequate before the battery went bad? Also, why not just replace the battery?

Not challenging your actions, just trying to understand your reasons and see if I would have done the same thing.

 

[bononos]

.........
I hadn't considered brownouts, of which there are also plenty. Wish me luck trying to figure out which UPS's are line-interactive. I think one store sells APC brand, so I can jot down model numbers and Google them at home. For the Thai brands I need to see if their web sites are in English.

Whats the difference between online and line-interactive?

Ah, that makes sense. I've assumed the highest load would be during boot, but what's to say that the power wouldn't "snap" during boot? Another thing I hadn't considered.

Thanks for the advise. As usual, in addition to answering my questions, you've brought up issues I hadn't factored in.

Like I said, the line interactive types will also perform some line conditioning to improve the quality of the power you are receiving. Here are the links I got from a search:
http://en.wikipedia.org/wiki/Uninterruptible_power_supply
http://www.smps.us/uninterruptible-power-supply.html
I'd get a line interactive one over the standby models because the cost diff seems to be very small. The online types start at a few hundred USD I think.

The line interactive types will probably have clues like AVR, line conditioning etc. Do a search on newegg/amazon for AVR/voltage regulation/line interactive UPS and you'll get a list and you can browse the features.

There was some controversy over whether stepped sine wave or square wave UPS could work with active/passive pfc psus. Someone who knows better could chime in but at this point I'm pretty sure the stepped/simulated waveform models are alright for active pfc psus (also your Abee brand of psu) at least for standby and line interactive ups'.

I doubt you'll need to go to the extent of getting a watt meter since you're not dimensioning a roomful of servers. A rough guesstimate or if you want to be more careful - some online power calculators like this one would do:
http://extreme.outervision.com/psucalculatorlite.jsp
The minimum psu wattage given would do since you don't have to factor in capacitor aging for your ups. And don't forget to add in your monitor (~20W).

 

[bononos]

I did some online shopping and found this page for a Thai UPS product line.

Why is a 1000VA unit only 400W? And, a 800VA unit is 300W?

(The ECO1000VA is ~US$80 and the ECO800VA is ~US$50.)

The APC models I see listed for sale jump from a 650VA/390Watt unit for ~US$105 and a 650VA/400Watt unit for ~US$115, to a 1100VA/660 Watt unit for ~US$180.

From what I gleaned above, the 650VA/390W APC unit should be big enough, right?

Reading the product info for the APC models, I see nothing about "line interactive," so they are "just a battery"? But, the cheaper Thai EMPOW brand is line interactive?

I don't know why the watt rating is so low either. I would've thought that the w rating is calculated from the putative power factor (~65%). I thought people with 80+ psus could even reduce their ups sizing requirements.

The 650VA/390W APC unit you linked has boost/trim/AVR in its specs which means that it is a line interactive type. Buck/boost circuit is another clue that the ups is line interactive. 390 is 60% of 650 so APC is assuming 60% power factor and since you're psu is 80+ you have have a more generous buffer in your sizing.

A discussion on stepped/square sine wave + pfc psus that I mentioned in passing earlier.
http://www.jonnyguru.com/forums/showthread.php?t=3964

 

[philipma1957]

I am a big fan of apc



http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BR1100CI-AS

you posted this one it is a little bit overkill but if you can afford it buy it.

this is a spec pdf for it.

http://www.apcmedia.com/salestools/ASTE-6Z7VBY_R1_EN.pdf


it uses stepped sine wave which is less pure sine wave. what is the make and model of your computer's power supply.



if you were in the usa I would say buy this:



http://www.ebay.com/itm/APC-SMART-U...pt=PCA_UPS&hash=item519b5eed36#ht_4870wt_1398


I use 3 units from this seller all have pure sine wave and are deeply discounted as they are rebuilds. this would be a great unit but shipping to Thailand would be silly . This seller ships to usa and canada

 

[dealcorn]

I know nothing of Thailand but at different times there is no shortage of brown outs in the Philippines which meant my home file server was almost always doing a post crash software raid resync. While there was never any data loss, I tried to order a UPS. I made a boo boo and got an affordable APC battery back up unit instead. I probably should replace it except almost all my problems were caused by transient issues which the battery backup fixes. About every other year power is gone long enough to drain the battery so my home server crashes but there has never been data loss and it is infrequent. For me, getting rid of transient issues was the big deal and that takes little in the way of battery capacity.

If your problem is 1 second flips, a battery backup unit with a small battery should cure that fine even if it is worthless for actual power outages.

 

[wpcoe]

The 650VA/390W APC unit you linked has boost/trim/AVR in its specs which means that it is a line interactive type. Buck/boost circuit is another clue that the ups is line interactive.

I'll certainly have to take your word on that. I have no idea what ANY of that means!

I'm tempted to get the 800VA/300W Thai UPS based solely on price, but probably will get an APC, simply because I know the name.

Do you have an opinion about the 650VA/390Watt APC unit or the 650VA/400Watt APC unit? Price isn't a factor, but I am clueless if anything else about them is!

 

[bononos]

I'll certainly have to take your word on that. I have no idea what ANY of that means!

I'm tempted to get the 800VA/300W Thai UPS based solely on price, but probably will get an APC, simply because I know the name.

Do you have an opinion about the 650VA/390Watt APC unit or the 650VA/400Watt APC unit? Price isn't a factor, but I am clueless if anything else about them is!

I'm not an expert either by any means (software guy), all I know is that they refer to features that peform some stabilization of the voltage coming in from your power utility. I got to finishing reading some discussions over ups/psus and think that some of my info is outdated. A good active pfc psu (which you have) is actually quite robust at handle brownouts and transient dips so all you might need is a standby UPS.

I don't know much about the units you linked. The 390w model is the BR650CI-AS and the 400W BK650-AS. The BR one is a line interactive type and the BK a standby type. You can post a question in the APC forums for feedback or search the net for review I guess.

 

[bigsnyder]

1. The 1000VA unit is highly recommended on this board.

2. I wanted a unit that I thought would be a better match for my system (more breathing room so to speak).

3. The price was right.

Why did you go up to a 1000VA UPS if the 600VA was adequate before the battery went bad? Also, why not just replace the battery?

Not challenging your actions, just trying to understand your reasons and see if I would have done the same thing.

 

[wpcoe]

FYI, the first response I got on the APC forum:

The "BR" line is a better option than the "BK" line. I would recommend the back up PRO line as these two UPS' will not support more than 390 watts. Although you may not use the full capacity of your power supply(600w), we don't recommend using a UPS that will not support it at full capacity. We would recommend either the BR1200GI or BR1500GI as they are the only two that support your power supply at full capacity.

Not sure I agree with needing to cover the full 600w rating of my PSU, but the BR product line got his vote. I looked at the physical specs and didn't realize the BR unit is 75% bigger (cubic dimension) and twice as heavy. From the pictures, I thought it was smaller.

I'm going to try, for once, to not over-think a purchase. I'm leaning toward the 390w BR unit, but will wait a bit longer to see if I get any other feedback at the APC forum. I had been hoping to get by with less than $100, but guess that won't be the case if I go with APC.

@bigsnyder: Thanks!

 

[TemjinGold]

Do note that unlike, PSUs, where oversizing grants you zero benefit (and can hurt), oversizing a UPS isn't worthless because it will mean longer up times versus a smaller unit. My current system can stay on for almost 30 mins after the power goes out, which is great if I really need to finish my work when there is no power!

 

[pandemonium]

I'm sorry, I edited my original post to clarify "add" instead of "multiply."

Here's a useful calculator for Watt or Amp loads.

 

[bononos]

FYI, the first response I got on the APC forum:

Not sure I agree with needing to cover the full 600w rating of my PSU, but the BR product line got his vote. I looked at the physical specs and didn't realize the BR unit is 75% bigger (cubic dimension) and twice as heavy. From the pictures, I thought it was smaller.

I'm going to try, for once, to not over-think a purchase. I'm leaning toward the 390w BR unit, but will wait a bit longer to see if I get any other feedback at the APC forum. I had been hoping to get by with less than $100, but guess that won't be the case if I go with APC.

@bigsnyder: Thanks!

The reply you from APC sound like a bog standard answer to shunt customers toward their higher end range and to avoid repercussions for underspecing.

I'm quite sure that APC specs on their website are not inflated and that the 390/400W rating is merely following a 60% power factor estimate. If an 80+ pf rating is assumed then the 650VA ups models could be rated as 520W capable. Your entire PC+monitor only consumes <300W (calculated with online psu calculator) running full tilt. Unless you were to upgrade your pc to take full advantage of your 600W psu rating, you wouldn't have a problem with the 650VA APC models. You can count the number of socket points on the 1200/1500 models vs the 650 and guess what makes sense.

So if you think your power is very flaky with frequent extended brownouts (<180v - cutoff point for battery transfer - user configurable to 160v - check the APC docs) lasting minutes or more, then you'd better not get the BR650CI-AS since the batteries only last about 4+minutes(300W) and they'll ko quickly under such conditions. You'll have to spend more for a larger ups with larger batteries to cope, or if you want to spend less - get a standby UPS like the BK650 which will not perform line conditioning and will only protect against surges/outages.

If your power is generally better- always >180v <266v with only occasional split second dips/outages which sounds like your situation then the BR650 or BK650 is ok.