Is it normal for my UPS to hum/buzz?

[elli]

I have an APC EasyUPS 1000VA.

 

My PC (~300W) and 27" monitor were plugged into it. Out of nowhere I heard a steady/constant low buzzing sound coming from the UPS. It was pretty quiet in my room so it was noticeable. The LED light on the power button was steadily on, but I panicked so I quickly shut down my PC and unplugged it + monitor from the UPS. No beeps, just a low buzzing/humming sound.

 

The buzzing sound lasted for about 5 minutes? And then stopped. We haven't had a power outage since I plugged it into the wall socket. I've had it plugged in for about 2 days now? Is this normal? 
 

Edit: It's a brand new UPS, bought earlier this month. 

[Alex Atkin UK]

Its normal for a UPS or any DC to AC inverter to humm/buzz when active.

You'll have to read the manual to see if its normal for it to become active at random, but its likely it does in order to test that everything is functioning properly rather than only finding out if/when you have a power cut and need to know its working.

[Biomecanoid]

A UPS can make a lot of different noises when charging batteries, when getting more voltage than normal, or when trying to pump up lower than expected voltage.

 

The most noticeable noise comes when the power is down and the UPS is powering your system.

[elli]

19 minutes ago, Alex Atkin UK said:

Its normal for a UPS or any DC to AC inverter to humm/buzz when active.

You'll have to read the manual to see if its normal for it to become active at random, but its likely it does in order to test that everything is functioning properly rather than only finding out if/when you have a power cut and need to know its working.

Oooh, thanks for the reply, I didn't know that.  
 

On the box it says that it has Automatic Diagnostic Testing, "bi-weekly testing of all internal components, including the battery, ensures your Easy UPS is ready when you need it." So I'm guessing maybe that could be it? 

[elli]

4 minutes ago, Biomecanoid said:

A UPS can make a lot of different noises when charging batteries, when getting more voltage than normal, or when trying to pump up lower than expected voltage.

 

The most noticeable noise comes when the power is down and the UPS is powering your system.

I see, thank you for the reply. I did not hear any beeps or tones at all, just that steady, low buzzing sound that lasted for a few minutes. I plugged my PC and monitor back in now and have turned the UPS back on and everything seems to be working fine, the low buzzing sound is gone. I don't really know what could have trigged it since we haven't had any power outages recently. And if it was operating on battery, I would have heard at least 4 beeps but I didn't, I was in my room before and when the buzzing noise started. Maybe it was the voltage regulation, but that's just a wild guess, lol.

 

On the box, it says it has Automatic Diagnostic Testing, "bi-weekly testing of all internal components, including the battery, ensures your Easy UPS is ready when you need it." There's really no description of what happens during that dx testing, but I'm guessing (from the other comment) that that could also cause the UPS to buzz.

[The_russian]

I have an APC Smart UPS 1500VA and that sounds like the self-test it does every two weeks like already mentioned. If it was a power outage it should have beeped. If it started humming/buzzing audibly for a bit then stopped, it was likely just a self test. 

[elli]

15 minutes ago, The_russian said:

I have an APC Smart UPS 1500VA and that sounds like the self-test it does every two weeks like already mentioned. If it was a power outage it should have beeped. If it started humming/buzzing audibly for a bit then stopped, it was likely just a self test. 

Got it. Thank you!

[Alex Atkin UK]

6 hours ago, The_russian said:

I have an APC Smart UPS 1500VA and that sounds like the self-test it does every two weeks like already mentioned. If it was a power outage it should have beeped. If it started humming/buzzing audibly for a bit then stopped, it was likely just a self test. 

Or possibly the mains voltage temporarily went too high or too low as most UPS will also kick in for that.

[Guest]

4 hours ago, Alex Atkin UK said:

Or possibly the mains voltage temporarily went too high or too low as most UPS will also kick in for that.

This was my thinking.  Whenever a line interactive UPS has to buck or boost, you'll hear a click and a buzz until mains voltage goes back to a nominal value.