An uninterruptible power supply as used in most server setups is an unremarkable and easily overlooked device. We mentioned the importance of a good UPS in one of our first blogposts over a year ago, and now we come full circle to examining UPS again. The other day we had to set up APC Powerchute UPS management software on a new server, as the server that previously ran it had been retired.
Shortly after setting this up we began noticing strange events in the event logs and receiving UPS alert emails:
Event Source: APCPBEAgent Event Id: 2007 "AVR Trim Active"
PowerChute Business Edition has detected the following event: Extended Overvoltage on Agent server.domain.local
If you receive these alerts, the first thing to do is check the UPS status on the Powerchute console, from Device Properties > UPS Status, and verify the input voltage the UPS is seeing. UK mains AC is nominal 230v, but for various reasons the allowable actual voltage may be -6% / +10% of this. Ideally you shouldn’t be seeing over around 253v regularly. If your input is within acceptable parameters you can suppress these alerts by adjusting the Powerchute Agent parameters.
APC say: “AVR Trim is when the UPS uses the internal transformer to decrease input voltage which may be too high. When the UPS switches to use this transformer, an internal relay makes a clicking sound. This is normal operation of the UPS reacting to too-high, or too-low voltage.”
In summary, AVR trim is a normal feature of APC Smart UPSs and should not affect the connected equipment. Monitor the input voltage your UPS sees to determine whether it is within acceptable variance. Configure appropriate alert threshholds to prevent spurious warnings.