UPS question

[FP]

Just picked up a 1500VA APC UPS from Office Depot.

I have my LCD, PC and routers plugged into the unit. Nothing too power hungry.

I plugged all of the items in before I turned the UPS on. When I pushed the power button on the UPS there was a click noise, the power light blinked and then the PSU in my PC made a fairly loud buzzing noise (an electric buzz). The UPS then clicked again, the buzz from the PSU went away and the power light on the UPS is solid (as it should be). All of the items I have plugged into the unit seem to be working.

My question is, is that loud buzzing from my PC's PSU be something to worry about? If I cycle the power to the UPS the same thing happens each time unless of course I unplug the PC from the UPS before I turn the UPS on.

Thanks.

 

[Lord Evermore]

What's happening is the UPS is testing its battery when you turn it on. Same thing will happen if you run the test with whatever button your UPS uses. Nothing to worry about. The battery doesn't put out exactly the same power that an AC outlet does. Was it loud enough that you'd hear it clearly sitting at the desk? Have you tried it with the UPS sitting farther away from the PC? Are you sure it was the PC buzzing and not the UPS (which I've usually seen)?

 

[FP]

Originally posted by: Lord Evermore
What's happening is the UPS is testing its battery when you turn it on. Same thing will happen if you run the test with whatever button your UPS uses. Nothing to worry about. The battery doesn't put out exactly the same power that an AC outlet does. Was it loud enough that you'd hear it clearly sitting at the desk? Have you tried it with the UPS sitting farther away from the PC? Are you sure it was the PC buzzing and not the UPS (which I've usually seen)?

Yep, you are right. The buzzing occurs whenever the UPS is on battery power.

All of the devices plugged into it emit the buzzing sound from their power supplies.

Did some research and it looks like it is due to the "approximated" sine wave power that is output from "cheaper" UPSs. There is some debate whether it causes any damage but the general consensus is that it won't cause any problems in the short time the devices are on battery during an outage.

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[Lord Evermore]

One should hope that we haven't been using UPSes all these years that were causing damage to equipment. 🙂 It may add to the wear on a power supply as it cleans up the power, but it's one of those things that you can't statistically prove because they still last longer than anybody ever uses them.

Whether you get a buzz does depend on what exactly you have plugged in. A lot of equipment doesn't care what type of waveform you send it, or may be very tolerant of lower or higher voltages than specified. Other equipment just plain won't work.

Note that "cheaper" UPSes refers to all consumer models, for the most part. Models that output a true sine wave are targeted at business servers and multiple machines, or high-end workstations.