I'm pretty inexperienced when it comes to setting up power for a network rack. I have a location that has a dedicated 20 amp circuit with a LP-20P socket. I have a APC UPS 3000XL rackmount UPS and a TripLite PDUMH20 PDU.

I'm looking at the current configuration where things are configured like this: [Power Source] --> [PDU] --> [UPS] --> [Network Gear].

I can't help but feel this is incorrect. Won't the UPS "obscure" the draw of all the downstream devices?

What is the correct power path for UPSs and PDUs? Does the UPS go to the PDU or the other way around? Does it make a difference?

1 Answer 1


Hmmm... I've usually plugged devices into the PDU then plugged the PDU into the UPS then plugged the UPS into the power source.

Can't really see it any other way.

  • Well like I said, the existing configuration has the equipment plugged into the UPS, and the UPS plugged into the PDU which is then plugged into the LP-20P socket on the wall.
    – user62491
    Jul 27, 2012 at 20:06
  • Right, but a PDU (power distribution unit) is meant to distribute power to the rack mounted devices, not to the UPS. When a UPS is in use it's typical to have the UPS plugged into the power source, then the PDU plugged into the UPS and finally, the devices plugged into the PDU. Is it the case that you're being provided with only a single circuit from the power source but that you have multiple UPS units? If not, then what's the point of the PDU in your scenario?
    – joeqwerty
    Jul 27, 2012 at 20:15
  • 1
    Agreed. That seems sensible to me. Just trying to figure out why someone would do it the other way around.
    – user62491
    Jul 27, 2012 at 22:13

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