BR1500G ups causing my power supply to buzz only when running on batteries inquiry

[MikePer]

Hi,

I've seen a couple of posts related to this topic but i wanted to confirm a couple of things that i didn't see in those other posts. I've a BR1500G UPS for over a year now.

According to the product page on amazon the APC BR1500G UPS is compatible with Active PCF power supplies and i'm unsure if this is related to specific power supplies since i had a RM850x and never had the issue at hand, but when i changed to a HX1000i the issue appeared. This happened overnight without moving the UPS or making any changes to it, but barely changing the computer since i just did a slight upgrade for the near future when i make a more significant upgrade on the computer (changing the GPU).

The computer now or in the near future will still pull around 850 watts so i really want to keep using this UPS just for surge protection and gracefully shutting down my pc when a power outtage happens.

My questions are: Why is the buzzing noise from the power supply started to happen? Is it because the current power supply is digital as opposed to the previous one which was mechanical? Can this struggle of the power supply when running on the UPS's batteries harm it if it's just used for about a minute or so? Isn't BR1500G a pure sine wave ups or that only applies to the SMART models?

And a final question is can the progammable mode for high sensitive equipments on the UPS be helpfull for this scenario?

Thanks in advance

[Teken]

Some insight and clarification as it relates to your question and problem. The APC BR1500G UPS you have in use outputs a modified (Stepped) sine wave - Not pure sine wave. The UPS is rated to output a maximum of 865 watts and based on your reply is at the peak of this units capability.

Like a regular 120 / 240 VAC circuit in your home its designed to sustain a continuous 80% load. The remaining 20% is intended for overhead to avoid the copper wiring in the wall from over heating and causing a fire. A UPS should be sized with no less than 30% extra power for the expected runtime when called to duty on battery power.

One thing that needs to be called out is the terrible marking by everyone in the UPS industry. Every UPS maker uses the VA rating vs Power rating to sell their wares. If you look at any so called 1500 VA UPS you'll note they all vary in (Power Output)??? 😖

That is because the VA has no direct relationship to power . . .

That is dictated by the topology, battery chemistry, and how efficient the overall design is! ☝️ You can literally find ten units with a 1500 VA rating and their power output will vary from 700 - 1400+ watts! Regardless, as you noted sensitive electronics don't like modified sine wave and will react by making noises, heating up, to just acting odd.

Lastly, the sensitivity option is to tell the UPS to transfer to battery power more or less often based on how *Dirty* the incoming power is. Setting it to low, med, high, also impact the longevity (service life) of the battery cells and how often they need to be replaced.