Advice on a UPS purchase

[LiuKangBakinPie]

Understand, but it helps to know what you're buying and especially when you could spend way more than is necessary to get the job done. Hopefully this discussion will help others, because seems to be a lot of room for confusion.

Agree. With electrical equipment its one way. You get what you pay for.

 

[alaricljs]

I can understand the power supply pulling more power than the output power that's being requested from it, but I don't understand why it would pull more than it's rated output power irregardless of load... (i.e. if you have a 600W power supply, but it's only being requested to supply 200W, why would it pull 750W and not 250W?) Then again, I'm not a power supply engineer 🙂.

The answer is in the term "in-rush", this is in reference to charging the capacitors. This is why it happens in only 8ms. Good PSUs with active PFC have a pretty impressive amount of capacitance.

 

[clicq]

The answer is in the term "in-rush", this is in reference to charging the capacitors. This is why it happens in only 8ms. Good PSUs with active PFC have a pretty impressive amount of capacitance.

OK, so the inrush current is related to the size of the capacitors in the PSU... so I can see why it would be related to the rated wattage of the power supply (I'm assuming more watts = bigger capacitors).

So it seems to me that the main concern is whether the UPS can switch to battery fast enough to prevent the capacitors in the power supply from losing charge. Since the SmartUPS devices are also line interactive, they should also be subject to the same problems right?

(APC claims the transfer time for the BackUPS RS series is 4-5ms http://nam-en.apc.com/app/answers/detail/a_id/7358/kw/switching%20time, and an older SmartUPS has a 4 ms max http://excessups.com/manuals/SmartUPS_1400_users_manual.pdf, so they don't seem to be that different... The Cyberpower UPS I used in the past claims a 4ms transfer time: http://www.cyberpowersystems.com/pr...?selectedTabId=specifications&imageI=#tab-box. APC probably wrote that warning for their lower end BackUPS line that takes 8-10ms to transfer to battery.)

I guess my point is, I think the inrush current isn't really an issue with the UPSes that are under consideration here.

 

[LiuKangBakinPie]

To determine how powerful of a UPS you need, first use the Journey Systems Power Supply Calculator to calculate your computer's wattage requirements. Take this number and add it to the wattage requirements for other devices you would plug into the UPS. Take this totaled number and check with the UPS manufacturer to find your estimated battery runtime when you lose power from the wall.

http://pcsupport.about.com/od/componentprofiles/p/ups_backup.htm

 

[MarkGinger]

I don't know if I just have a freak one or if it is normal, but I'm still on the original battery in my APC 725VA unit that is nearly 5 years old now, and it still works. Probably have lost a couple minutes of runtime but I'll still get almost 10 min out of it which is enough.

Hey, if it works don't fix it! A little run time sacrifice is ok, but 10 minutes of run time is excellent.

 

[MarkGinger]

Honestly, power filtration and surge protection are secondary concerns. I just want to have the ability to shut down cleanly when a power outage occurs, so really only need a few minutes max. But I don't want to sacrifice power quality during normal runtime for that protection (if that makes sense). I have pretty clean power at my house, but invariably there will be a 20 minute outage once every couple of months (and usually on days with perfect weather). I thought about disabling write cache on my drives to minimize data corruption, but I don't think it's worth doing.

Don't disable write cache on your drives, that's unnecessary. Either of the above mentioned Smart-UPS units will do a fantastic job protecting your machine.

 

[MarkGinger]

I'm glad I posted the question now. Doesn't seem like a clear consensus on simulated sine wave UPS's with active PFC PSUs. Gonna put that credit card back in the wallet... Wondering now if the difference between simulated and pure is more of a benchmark difference than a real world difference.

You're better off getting the Smart-UPS protection than not. You can't lose by having a better quality UPS that will protect your system better than the smaller home use UPSs.

 

[PurdueRy]

I am liking my Cyberpower:

http://www.amazon.com/CyberPower-CP1...7273420&sr=8-2

Active PFC, fairly small, and enough power to run my computer with peripherals and two monitors for 15 minutes. If the monitors are off it can run for 30 minutes.