SU 1500 electrical buzzing sound

[Anonymous user]

I just noticed an electrical buzzing (almost arcing) sound coming from my SU 1500. It comes on when the unit is plugged in, regardless of whether the unit is operating or off. It goes off for a second or two every so often, and then continues. It might be coming from the speaker/buzzer horn as well, but not sure. Any suggestions or recommendation? Unit appears to function normally besides this sound. Thanks in advance.

[BillP]

Hello,

How long has this been happening?

You said that this only happens when its plugged in so when it is unplugged you NEVER hear anything?
*If it were to continue while unplugged, you could try holding the off (o) button with the unit off, equipment disconnected, and unplugged and see if it stops. If it does, plug it in again an see if it continues.

When the unit is on, there should be some audible noise of course but not a loud obnoxious buzzing, especially when it is off.

After trying the above to no avail, turn the UPS off, and unplug it from the wall, I would check behind the front bezel and see if there is anything loose with the battery connections.

Other than that, there's nothing else that you can do and may want to consider a replacement.

[BillP]

I have two SU 1400 RM 2Us and one does the EXACT same thing. I can hear a slight buzzing sound from the back of the UPS near the power plug and managent slot.

It occurs when I plug the UPS in whether it is turned on or not. Otherwise the UPS performs well, temps are normal, runtime calibration goes to completion.

I did notice that the output voltage fluctuates though... it doesn't do this on my older SU 1400RM 3Us.

Should I be worried about the buzzing sound?

[BillP · Accepted solution]

How much does the output voltage fluctuate?

I mean, there should be a slight buzzing/humming during normal operation, especially while on battery during an outage or self test. But on the other hand, if its noticeably louder than other ones you have, then its not normal. Also, the fact that it happens with the UPS is off is another kicker as well.

Can you pinpoint when this started happening, possibly after moving it or something? Also, if I am not mistaken, I believe that there is a fan on this model? Doesnt make sense to be that though when the unit turns off.

It also could be something like the inverter which converts the DC voltage to AC, especially since you are seeing output voltage fluctuations.

From my standpoint, I'd suggest taking it out of operation because even though I have heard similar noises and everything turns out to be fine, I wouldnt recommend risking it if we can't narrow it down to something specific.

If anyone else on here can help narrow this down from experience, please jump in.