APC AP7954 Switched Rack PDU Internal Power Supply #1/#2 Fault

[scottclarke_apc]

This was originally posted on APC forums on 10/23/2017

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Hi All,

I've seen some SMTP alerts over the weekend from one of our switched rack PDU's about an internal power supply fault. Can someone please provide some advice on how to remediate this issue? The PDU in question is sending alerts about supply #1 and supply #2 every two minutes.

Thanks in advance.

[BillP · Accepted solution]

This reply was originally posted by Angela on APC forums on 10/23/2017

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Hello,

Unfortunately, this typically means that the Rack PDU needs to be replaced. How old is this PDU and how long has it been in service? 

Here is some additional background (with an important part underlined specific to what you've described here):

Metered/Switched Rack PDUs and Automatic Transfer Switches contain power supplies that are intended to monitor the current being passed through the PDU/ATS, display module, and to control outlet relays (if supported). There is a primary and a secondary power supply. 

The life of the power supply itself is difficult to predict due to the damage from power surges. For these types of devices, the power supply failure rate is low but failures happen most often on these circuits. The design life can be affected by how the Rack PDU is powered. A UPS powered Rack PDU will generally have a longer life than Rack PDU connected directly to utility power. APC Rack PDUs provide redundant power supplies if a single power supply fails, the secondary can take over until the user is able to replace the PDU. If both power supplies fail on a Switched Rack PDU, on the next power cycle, the outlets will turn off because the outlet relays require DC voltage to energize.

When these power supplies or the communications bus they use fail, a message will be displayed in the event log or web UI, indicating which one has gone bad. Also, the message "Er" will be displayed on the front screen on AP78XX and AP79XX models as well as Rack ATS models with a 7-segment display.