View Single Post
Old 11-29-2021, 09:12 AM   #50
Badcaps Veteran
Join Date: Oct 2009
City & State: Thessaloniki, Greece
My Country: Greece
Line Voltage: 230VAC 50Hz
I'm a: Knowledge Seeker
Posts: 2,137
Default Re: Powerware 9120 Online UPS

It is not recommended to try to make this Online UPS unit more silent.

The fan is always loud on Online type UPSs for a reason. It's loud to cool the inverter that takes the DC and converts it back to (perfect) sine wave AC that goes to your devices.

You can go to the menu and select high efficiency mode. This converts it to line interactive unit somehow , the inverter is not working all the time and your devices get mains AC this is why it is also called bypass mode. This works until the micro-controller senses that there is something wrong with the quality of the AC , you can set the upper and lower voltage limit and maybe also the Hz limit. When voltage is lower or higher than the limit you set on the menu, it will turn on the inverter and switch to it.

Same goes with Hz. When it senses that the frequency of the AC is not close enough to 50Hz it will do the same. But by setting it to High efficiency mode it partially defeats the purpose of having an online UPS in the first place.
goodpsusearch is offline   Reply With Quote