Single Phase PDU & Rack Power [APPLICATION NOTE LINK INSIDE]

How do you balance the electrical needs of a cabinet of equipment with available technology?  Many data center facilities have come to rely on a standard rack mount power strip PDU configuration fed by 3-phase, 30A circuits running at 208V.  This setup can yield approximately 8 kW to feed your power-hungry IT gear.

Not bad.  But the problem is that you’ll go through pole positions faster than freshmen through tater tots in a high school cafeteria.

Although the 30A 3-phase approach is deployable and commonly used, the reality is that it is not the most efficient approach in the world of breaker panel resources.  To optimize your build, there is an alternate approach using higher ampacity and yielding more power out of fewer breakers.  We’re talking about 1-phase PDUs at 60A.

Wait, what?

Yes, Server Technology offers a 60 amp single-phase PDU that also runs at 208V.  This configuration is available in HDOT, or high-density outlet technology, which allows the user to take advantage of the power gains by specifying up to 54 outlets in a single intelligent PDU.

So, what about power?  The 1ph 60A approach is a 10kW PDU, which provides 20% more power and current flow than the 3-phase 30A that only yielded 8kW. 

And breaker utilization?  Here is where things get even more interesting.  Instead of taking the three breakers required per circuit in the 30A configuration, a 60A feed requires only 2 poles to get the job done.  So in a typical redundant feed with two PDUs per rack, that is 4 poles on the 60A side versus the 6 required at 30A — a panel space savings of 2 poles per rack. 

In other words, for every rack deployed at 60A you save one rack PDU worth of power.  And a whole lot of ketchup.