We have bought a few 30amp 208v PDUs that only have 9 receptacles. The servers we are connecting to those PDUs will not use the full 30amps (at 80%, or actually 40% since we use redundant power) so we need to find a way to connect more than 9 servers to the same 9 receptacles so we'll be not wasting capacity that we pay for.
I thought about using a Y split cable like this one: http://www.cablesandkits.com/power-cord-c14-c13-splitter-cable-awg-p-515.html
That will let me connect two servers to a single receptacle.
Each of the individual receptacles can provide 12 amps of power and individual servers are unlikely to consume more than 3 amps at maximal load so it should provide sufficient power.
The question is if there is any other reason why this may be a bad idea and if there is any other solution other than buying PDUs with more receptacles (which I don't want to do because I must use horizontal PDU on these racks and ones with more receptacles consume more U space).