Short description of the problem, my PCs switches off when my UPS switches to battery when faced with an overvoltage on the mains Line. The PC does not switch off in case of a power failure and the UPS switches to battery mode.
Long description
I have 2 backup sources of power in my house.
1 - Inverter (working in UPS mode) This has a switchover time of <= 8ms as per specification. This provides backup to the lights and fans in the house and also to my pfsense server (This is an old PC repurposed for Pfsense). This is because the inverter has a backup time of a few hours compared to the dedicated UPS which has a backup of about 30 minutes.
2 - Back-UPS RS 1500G-IN - this has a switch over spec of 6 ms typical and 10 ms maximum. This provides backup to my main PC AMD X570 with Ryzen 5900x CPU with Antec HCG 850M Gold EC
Now the voltage from the mains at my place goes up during the evenings from the standard 230V it reached around 255V (as seen on the APC UPS display). First thing i notice was my main PC suddenly switched off for no reason then i notice that my APC UPS had switched to battery mode.
Almost immediately my PFsense machine also switched off (but the inverter did not sound any alarm (beep) of switching to battery)
Now i restarted everything and 5 minutes later again the same sequence repeated.
So after some time i restarted both machines and then switched of the main power supply and both my Pfsense machine and my main PC continued to function normally as the UPS and inverter switched to battery.
This has happened a couple of times before
I just cant figure out why the PCs are shutting down inspite of have backup power source (UPS/inverter) when the switch to battery happens during over voltage, but it works fine when there is a power failure. Only thing I can think of is, is the switchover time or mechanism different in case of over voltage compared to a power failure.
this is not a load issue as the load on the UPS is around 25%. I cant measure the load on the inverter but it usually beeps if there is an overload which it did not
Has anyone faced an issue like this or have any idea why this is happening and how to avoid this.
I think what is going on here is either the UPS isn’t sufficient when switching to battery power or the PC is very sensitive to power changes from the UPS. Or both.
But what i cant figure out is why is this issue coming only in the case of Over Voltage switchover. It works fine in the case of power failure switchover.
Sounds like your PSUs are more sensitive to the voltage range than what the UPS is allowing for under ‘normal’ conditions or before deciding to switch over to battery. I wonder what some of the transient voltages are reaching if your UPS displays 255V averages at times.
With some UPSs you can adjust the sensitivity range, or set it to a high sensitivity mode - to narrow the acceptable voltage & frequency range. Even if you can adjust your particular UPS though, you’re then probably going to run into on-battery run-time issues if you suffer from prolonged over voltage conditions.
You might have to look into changing that Line Interactive UPS to a True Online aka Double Conversion UPS.
Line Interactive will pass through AC under normal conditions, unless switched over to battery when voltages/frequency are out of range.
Double Conversion is permanently converting input AC to DC and then DC back to output AC again - effectively ‘filtering out’ transients, frequency changes, etc, with no changeover delay.
Strange because most power supplies these days are switching supplies with a big input range. Is the voltage increase going above the power supply rating? Many are only up to 230 volts AV here in the USA, and I’ve seen people getting 250 volts in the UK.
The operation mode of the UPS as detailed above is also worth checking.
Yes the rating for the PSU is upto 240V but it works fine above the rated capacity. Its only when the switchover that this happens that its. I guess i have to use a voltage regulator on my mains to limit the voltage to 230V.
I have two UPS, and both are behaving oddly too. At first, I thought it was bad batteries, so I changed all of them, but the problem persisted. As soon the power goes down, both UPS performs as they should. But when the power comes back, they can´t handle the peak surge and shut down. As the mains voltage stabilizes, they go online again, but the computers they intend to maintain are long gone off. I think they are already old and faulty, so I am planning to replace at least one of them.
Your incoming voltage is too high. I would complain to the utility company. Reference ANSI Standard C84.1 - This standard is what the utility is required to follow. 252v is the max (at the service entrance) from the utility. Really they should keep it lower than 252v but C84.1 is the standard.
