"thunk" noise comes from Smart UPS 1000 when voltage is low

[Anonymous user]

Just wondering if this is normal. A repeating "thunk" noise comes from my Smart UPS 1000 when the unit registers low voltage. The thunking lasts as long as the low voltage situation. The thunking is definitely not the clicking noise I am used to when my Smart UPS 700 registered low voltage.

[Anonymous user]

Thanks for your response.

Yes, the "thunk ... thunk ... thunk", at seemingly regular intervals, occurs during avr boost mode.

Message was edited by: bpvh

[BillP]

The older smart upses would switch instantly back once the problem is solved, so i have had the repeted thunk on one of my my smart upses once it kept flashing avr boost to online: The actual cause of this is a bad sine wave, that would be caused by a item on the curcit putting noise into the line, or a problem with the power company, i can make my smart ups do this when applying a square wave to the unit.

[Anonymous user]

Thanks again.

Just knowing its not an issue with the UPS is a great relief.

Now, to find out what's causing the bad power.

[BillP]

I never thought to post about the "thunk" noise which I sometimes hear on my SUA2200RM2U but it's good to know that it's normal. 😉

[BillP · Accepted solution]

The thunk is from the relay, you have to remember the more power the unit has to output the bigger relay it will need, my rackmount smart ups makes a very loud "thunk".
Now are you referring to the humming of the unit when using avr boost mode?