Choosing the right UPS

[Mark TW]

Hi all, with all the potential electric disturbances this coming winter I am going to buy a UPS to protect my PC. The PC and monitor uses about 230w alone plus I need to plug my speakers and scanner into the UPS, also the PSU in my PC is 550w but Im not sure that makes a difference anyway.

So what wattage UPS do I need? I was looking at the 400w one, Would that be enough?

Also any brand recommendations would be appreciated, I heard APC are good, someone else said they'd gone downhill in recent times though

Thanks
Mark

 

[VersionMonkey]

What's your aim - keep the power on just long enough to be able to cleanly shut down, or to be able to carry on working during an extended outage? If it's just to shut down, then you probably don't need to consider peripherals (just keep them plugged directly into the wall); only the PC and monitor.

When sizing the UPS you need to keep in mind a couple of things - the first of which is that manufacturers often quote a power rating in VA, not W and you may have to dig into the specifications to get the actual rating in W. The practical effect of which is that, when considering the power draw of the equipment you want to support in W, you probably need to oversize the UPS in VA by at least a third as the manufacturers assume a very poor power factor.

So, for example, if you want to support equipment drawing 500W, you should look to a UPS rated at least to 750VA.

The other is that if you are close to the rated power of the UPS, you can generally expect only a few minutes run time on battery - enough to save what you are doing and shut down.

You can get more run time by oversizing the UPS further (e.g. go to 1000VA for a 500W load), but that is often less efficient. You can get extended runtime models which have a larger battery, which is the "right" way to extend runtime, but they tend to cost disproportionately more.

Only APC UPS I've had problems with was one of their bottom-end Back-UPS models. Smart-UPS and even Back-UPS Pro still seem OK. I've also used Emerson and Liebert UPSs without issue in the past.

Worst UPS I've ever come across was a Belkin.

 

[Mark TW]

Hi, thanks for that extensive answer. Yes, the aim is just to shut down safely, not too bothered about extended running time, just protecting my PC from surges, black outs and brown outs.
The 400w UPS I was looking at has a VA of 650. Would that be too much for what I need? Would it put my equipment in danger? The model down from it is 240W and 400Va, maybe that's the way to go? Sorry if these questions seem really dumb, I have a poor understanding of electricity! :-S

 

[VersionMonkey]

Oversizing the UPS is perfectly safe - the rating is just the maximum power that can be drawn by the equipment connected to it. Anything up to that is fine.

You do need to be wary of undersizing the UPS. If your equipment were to attempt to draw more than the rating, then the UPS would likely cut power to the equipment (which is the exact opposite of what you want!). As a result, you need to look at the peak possible load from the equipment and size according to that.

If your 230W figure is definately the maximum your PC and monitor combined will ever draw (even momentarily), then you might just get away with the smaller, 400VA, UPS. But I would not recommend it. Between the two and based on a 230W peak load, go with the 650VA.

 

[Mark TW]

Ok, great, thank you for taking the time to answer with such good info. Much appreciated!

 

[V F]

Hi all, with all the potential electric disturbances this coming winter I am going to buy a UPS to protect my PC.

Funny the thought of that if it comes to be. Imagine the thought of that updating the firmware on items...

 

[lsg1r]

If it's just to shut down, then you probably don't need to consider peripherals (just keep them plugged directly into the wall); only the PC and monitor.

Except for things like an external hard drive or nas.... spinning disks really hate power cuts

@Mark TW ... personally I've had no real issues with either apc or belkin but I'd swing towards apc or eaton these days.

 

[Mark TW]

Except for things like an external hard drive or nas.... spinning disks really hate power cuts

@Mark TW ... personally I've had no real issues with either apc or belkin but I'd swing towards apc or eaton these days.

Ok cool, thanks!

 

[EsaT]

The model down from it is 240W and 400Va, maybe that's the way to go?

Never size UPS tightly.

You can't be sure if transfer to battery operation would be succesfull when nearing specified max load.
There's time delay before UPS starts providing output voltage and during that time power supplies of PC and monitor are drawing power from their primary/bulk capacitor.
And once input voltage returns power supply likely draws higher surge to recharge that capacitance.
(from cold start that surge is decimal position higher than nominal current draw)

Also you can be sure that battery size is minimal and UPS likely won't take battery aging/wearing well possibly degrading actual available output power fast in few years.
Higher than mandatory size UPS has more battery capacity and aging/wear of it doesn't form problem risk as fast.


If you want to use normal main power plugs instead of getting IEC connector power cables there aren't that many possibilities.

Like some APCs, Cyberpower BRIC has UK sockets.

BRICs LCD - Backup UPS Systems | CyberPower

The UPS adopts CyberPower's patented GreenPower UPS™ technology to enhance UPS operating efficiency, reduce heat generation, consume less power and save more energy costs than conventional UPS models.

www.cyberpower.com

Unlike APCs Back-UPS, those are line-interactive.
AVR functionality does some voltage regulating, like correct smaller brownouts without need to transfer to battery.
Also they have faster transfer time to battery operation, because there's no mechanical switch between inverter and load.

Line-interactive vs Online vs Offline UPS | FS Community

There are three topologies of UPS systems: offline vs line-interactive vs online. What are their differences and how to choose the right UPS system for your design? This article will make a comparison among these three designs in four aspects: operating principles; functions; benefits and...

community.fs.com

You can get more run time by oversizing the UPS further (e.g. go to 1000VA for a 500W load), but that is often less efficient.

For offline/standby and line-interactive consumer UPSes that doesn't really matter, because power draw on UPS control circuitry doesn't grow with its output size.

 

[Mark TW]

Never size UPS tightly.

You can't be sure if transfer to battery operation would be succesfull when nearing specified max load.
There's time delay before UPS starts providing output voltage and during that time power supplies of PC and monitor are drawing power from their primary/bulk capacitor.
And once input voltage returns power supply likely draws higher surge to recharge that capacitance.
(from cold start that surge is decimal position higher than nominal current draw)

Also you can be sure that battery size is minimal and UPS likely won't take battery aging/wearing well possibly degrading actual available output power fast in few years.
Higher than mandatory size UPS has more battery capacity and aging/wear of it doesn't form problem risk as fast.


If you want to use normal main power plugs instead of getting IEC connector power cables there aren't that many possibilities.

Like some APCs, Cyberpower BRIC has UK sockets.

BRICs LCD - Backup UPS Systems | CyberPower

The UPS adopts CyberPower's patented GreenPower UPS™ technology to enhance UPS operating efficiency, reduce heat generation, consume less power and save more energy costs than conventional UPS models.

www.cyberpower.com

Unlike APCs Back-UPS, those are line-interactive.
AVR functionality does some voltage regulating, like correct smaller brownouts without need to transfer to battery.
Also they have faster transfer time to battery operation, because there's no mechanical switch between inverter and load.

Line-interactive vs Online vs Offline UPS | FS Community

There are three topologies of UPS systems: offline vs line-interactive vs online. What are their differences and how to choose the right UPS system for your design? This article will make a comparison among these three designs in four aspects: operating principles; functions; benefits and...

community.fs.com

For offline/standby and line-interactive consumer UPSes that doesn't really matter, because power draw on UPS control circuitry doesn't grow with its output

Definitely a bit of a minefield but that's helped a lot! Thank you

 

[White_Widow]

400w should be enough for your setup. APC is still a good brand, but there are other good brands out there as well. CyberPower, Tripp Lite, and Eaton are all good brands that make quality UPSs.