Need some UPS advice

[Nate4747]

Hello. I have a 24" iMac and I have just bought an APC 500VA 300 watt UPS unit. I wasn't looking for long term battery backup, just surge protection and something to stop my computer and external drives from going down hard in an outage. The unit (much to my surprise) runs the iMac for about 20 minutes at lowest brightness.

When it is on battery, however, the power supply on the iMac hums. I'm not sure what this means, but I suspect it is from insufficient power. I'm wondering if it could cause damage to the mac? How is one supposed to decide on a UPS based on the VA rating? If anyone knows a lot about UPS' and can give me some advice that would be great. The 24" iMac draws 220W max.

 

[jsw]

My UPS hums when on battery... you're certain it's the iMac making the noise? Just curious....

 

[ITASOR]

My UPS hums when on battery... you're certain it's the iMac making the noise? Just curious....

Yeah, same here, I thought my MacBook's power supply wasn't working right, but when my UPS switches to battery power, the actually battery (I assume) hums.

 

[Nate4747]

I'm pretty sure it's the Mac. It may just be this mac though because it's defective and it's going back to Apple on Monday, perhaps it's a total coincidence. I'm curious what VA is your UPS and what kind of computer is it powering?

 

[bankshot]

Every UPS I've used has made some sort of hum when running on battery power. Some were quiet but still audible (my Belkin at home), others sounded almost like a little mini-fridge (APC units at work). It's quite likely that everything's operating normally.

I've also noticed that recent Apple power supplies tend to amplify noise coming in on the line, either from the power side or from the computer side. In particular, this occurs with the Macbook/Macbook Pro whine noise. The power supply brick tends to amplify it louder than the actual computer.

 

[Nate4747]

Every UPS I've used has made some sort of hum when running on battery power. Some were quiet but still audible (my Belkin at home), others sounded almost like a little mini-fridge (APC units at work). It's quite likely that everything's operating normally.

Well this is an APC so maybe it is normal. It's my first UPS purchase so I really didn't know what to expect. My precious experience with computer hardware has been never-before-heard sounds == bad, but I guess I was wrong in this case. Thanks for the input.

 

[ljump12]

Use USPS instead