Choosing an UPS

[Shilohen]

Hi all,

I don't know if this belong to general hardware but since it's linked to power, I thought it would be more fit here.

I'm slowly choosing parts for a new rig and I want to buy and UPS to prevent potential data loss (I heard that some SSDs really dislike sudden power shortage). I'm still undecided between an AX850 and an AX1200 PSU since the GPU or the SLI/XFire choice is not yet cemented either. Anyway, I was wondering if an UPS must have a power rating equals or greater than the PSU because most seem to be around 750W, greatly limiting my options if this is indeed the case. Any opinion/suggestion would be welcomed.


Thanks!

 

[SOSTrooper]

No you do not need to get a UPS with same or greater power rating than the power supply. On my other computer I have an APC 1200 which is rated at 720W (for my Corsair 850W) and it's been working great. I have the computer and LCD plugged into the battery outlet and the APC program shows that the computer is only drawing ~150W when it's not under full load. I think as long as you get a capable UPS you'll be fine even if running the AX1200. It's not like you'll do full load when the electricity is out.

 

[Shilohen]

Thanks, that's exactly what I wanted to know.

 

[jonnyGURU]

The problem with overloading a UPS even when the power is NOT out is the alarm that tells you that you're overloading the UPS.

I have a GTX 285, Core 2 Quad and four HDD's (was five, but one died) on a SilverStone 1000W plugged into a 685AVR CyberPower. When I game... on wall power.... the overload alarm beeps at me telling me that the UPS is overloaded.

Remember: Your DC output capability is only about 80% of your AC consumption, so if your PC is using a 600W PSU to about 85% capacity, say 500W, you're still pulling 630W from the wall. Not that you need a 1500W UPS for a 1200W PSU, but if you put a 800VA UPS on that PC and the alarm never goes off, you probably could've gotten away with a 750W PSU.

 

[Shilohen]

I guess so, but I want to get the best efficiency possible as well, so I need to aim at an average load at 50% of the PSU spec. The AX850 would be pretty perfect for that if I don't XFire/SLI and only mildly OC. Yet, if I go with the AX1200 and don't SLI/XFire then I won't get a so good efficiency either. All in all, I hope to never go above 750W so the alarm issue might be a moot point, but still very nice to know.

I'm getting more inclined toward the AX850 route. After all, even if I go with 2 GPU, they won't always be at full load.

 

[jonnyGURU]

You do realize that this 1 to 2% efficiency difference is only worth about 3 cents per year, right. You're better off at 70% efficiency and a good 750W, Corsair AX or not, is more than enough.

 

[Shilohen]

Yeah, it's not really for the money, it's more for the noise, heat and green, but I might reconsider if there's a killer deal when it's time to pull the trigger.