Smart-UPS SRT 10000 output frequency dropping over time

[jwalker55]

We have 2 Smart-UPS SRT 10000's. 

In looking at historical monitoring data, we noticed the output frequency on both of these units has been steadily dropping ever since we installed them. One is currently showing 56hz, while the other 55.8hz. Input frequency is a fairly stable 60hz.

Attached is a graph showing input and output frequency from November 2018 to present. Blue line is input, green line is output. I have not seen anything like this on any other UPS. I can't fathom this is normal in any way? Anyone seen anything like this?

[Username2]

Have the exact same problem with two APC UPS SMT1000IC on different locations. Would really like to know whats going on....

[jwalker55]

This appears to be some kind of firmware issue. I did a complete power cycle on one of the units by shutting off the breaker to it and then powering it off and back on. It now reports 60hz again. I did test one of the receptacles on the unit prior to the power cycle and it read 60hz, so I think the issue is something to do with how the firmware is calculating or reading the output frequency. Note: rebooting the NMC had no effect.