Smart-UPS 3000 adjust output upper limit

[BillP]

We've been getting lots of notifications indicating that our UPS is compensating for a high input voltage, especially overnight.  According to the logs the highest voltage we've seen is 127.39V (listed in the VMAX column).  Afterwards the voltage drops but the over voltage compensation (along with the notifications) doesn't stop until the VMAX drops to under 125V.

We've decided we'd like to only be notified if the voltage hits 128V, so I've adjusted the Output Upper Limit to 128V.  However, last night we received notifications again even though the highest value reported in the VMAX column is 126.68V.

Why is the UPS compensating for high voltage at 126.68V even though we've set the Output Upper Limit to 128V?

What am I missing?

[voidstar_apc]

You can't trust the V_max column -- it's sampled slower than the UPS responds to voltage changes.

[BillP]

Then what is the most accurate way to find out what the UPS is seeing for a high voltage?

[voidstar_apc]

The most accurate way to see what's happening is an oscilloscope connected the line and triggered by the AVR relay. Not very practical though. Personally I wish the SmartUPS' logged the waveform that triggers a transfer. It's not necessary for proper operation of the UPS but would answer questions like yours.

[BillP · Accepted solution]

You could also test the UPS if you had access to a Variac or similar way to adjust the input voltage to the UPS.  Plug the UPS into the Variac and monitor the Variac's output with an accurate voltmeter and turn it up until the UPS starts working its magic.