APC Ups 750VA making annoying humming noises!

[L33tPilot]

I currently have an APC UPS 500VA 300watt UPS. It works fine, but very little battery life. I use it to maintain good quality electricity on the line and to quickly shut down my computer in the event of a power outage. At 1minute, the computer shuts down and leaves the UPS with about 60% battery. No biggie, it does the job.

I just bought a 750VA 450watt power supply for some more juice. When I pull the power on it, in addition to the UPS itself making a humming noise, my power supply in the desktop, lcd, and printer make a humming noise.

Why is this happening and more importantly is it hurting my electronics? I took out the new one and put my 500VA back that doesn't have this problem.

Any info would help.

Thanks,
Ryan

 

[L33tPilot]

ttt

 

[L33tPilot]

ttt

 

[Zepper]

What brand/model is the 750VA unit? IAC, it sounds like the DC/AC converter isn't working as it should. I'd exchange it if you're within the time frame. I recently bought a CyberPower 550VA and it's pretty quiet on line or battery power (except the usual hum from a high-current transformer) - no untoward sound effects from the connected equipment either. I tried to power an old cordless phone from it and it is kind of noisy in the ear, not making any humming noise (it wasn't really designed to tolerate the stepped square waves that most of the inexpensive battery backup units produce for output) but did work. One tip: If you value your computer and other gear, avoid Belkin power equipment, so if that's what you got I'd try to get a refund and buy something else... OIC, it's an APC, then just exchange it for another unit.

.bh.

 

[L33tPilot]

this happens in a bunch of different model apc's, and most are new. it also happens on more than one of my computer

APC is kind of stumped. I'm thinking it's because I'm pulling the AC plug, thus losing the ground connection. I wish I knew if that humming was bad.

 

[Zepper]

You can get a short power cord adapter from http://www.CyberGuys.com that connects only the ground wire or you can make one. And yes, the ground should be maintained for best operation of your computer equipment and the UPS - a true power outage looks like a near short of the hot and neutral lines (the resistance of the transformer winding at the utility pole and the wiring to it), not an open, circuit to the battery backup. Or you could put a totally passive power strip between the UPS and the wall - the switch on that will disconnect at least the hot and maybe both hot and neutral while leaving the ground intact. I assume you're pulling the plug for an uptime test or some such.
. The UPS companies say you shouldn't put anything between the UPS and the wall, but I use a CyberPower surge strip for extra protection and for doing uptime tests. Just be careful not to accidentally trip the switch on it as your battery will cut in.

.bh.