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After upgrading firmware on my APC AP8XXX series Rack PDU, the input voltage reads 1V


Upon upgrading AP8XXX Rack PDU firmware from v5.X.X to v6.0.9 or v6.1.0, the input voltage reading shows 1V. (This also causes Power Factor to read approximately 0.10 and device load to show approximately 0 as well.) Please see examples below.

Product Line
  • Rack Power Distribution
    • AP8XXX series

  • All serial numbers
  • Upgrade scenarios from v5.X.X firmware to rpdu2g APP v6.0.9 or v6.1.0


This is due to a firmware issue which typically affects high density AP8XXX series Rack PDUs with high load and high ambient temperature. Upon a firmware upgrade, the Rack PDU phase metering chip (located in the PDU chassis) does not initialize properly, causing the PDU input voltage to mistakenly read 1V. This affects subsequent calculations and readings that utilize the input voltage value including device load and power factor. After downgrading back to v5.X.X, the voltage reads normally.


This issue has been addressed in rpdu2g firmware APP v6.3.3 and higher. This update is available https://www.apc.com/tools/download/index.cfm as of June, 2015.

If you are unable to upgrade immediately for some reason, APC Rack PDU engineering has been able to fix the issue by reducing the load on the Rack PDU, reducing the ambient temperature, or power cycling the entire Rack PDU for 5-10 seconds.

Alternatively, downgrading the Rack PDU to rpdu2g v5.1.6 is a viable solution if none of the above can be completed prior to applying the firmware fix, when available. If you consider downgrading your Rack PDU from v6.X.X. to v5.X.X, please read this knowledge base article ID -> FA167693.

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