Problem with ES-550

[Anonymous user]

5 days ago I experienced strange behavior of my UPS system: accidentally PC and LCD connected to my UPS immediately shut down, while UPS made strange constant noise (weird kind of buzzing). Green led on UPS was shining, indicating that the power is on, but any of both Power / Reset buttons did not react. I disconnected the power cord of the UPS from the wall socket - nothing happened, noise did not disappear. Then I removed power cords from the UPS, starting with the router and voila - strange noise stopped. Then, when I turn the PC on and check the PowerChute Problem History I see no informations about the event - just 0 power problems. My question is - is it really possible that router could cause such a strange behaviour? It must be said that the PC was in idle, CPU load was zero nothing, I was reading some webpage, also network activity was near zero (no downloading, streaming etc.).
I have UPC Back-UPS ES-550 with serial nr 5B0802T07458, firmware 828.D2.I and PowerChute PE v3.0 with following configuration:
A) in battery backup & surge protection are connected:
- PC with Fortron 400 W PSU
- LCD Acer S243HL (18 W)
- Router Asus RT-N16 (15 W)
B) in surge protection only are connected:
- switch Signamax 065-7025B (7 W)
- speakers Logitech X230 (32 W)
- set top box Motorola VIP1910 (10 W)
C) PowerChute settings:
- "Keep my computer as long as possible", 8 min
- "Disable battery backup alarms when PC is off or hibernated"
- "Sensitivity - Medium"
- "Voltage 196-260V"

[BillP · Accepted solution]

Typically, when a UPS emits a high pitch tone it indicates that it got overloaded.