C13 vs C14

They are not two names for the same plug. They are the two ends of the common 10 A IEC 60320 pair.

Which end goes where

Into the server	The C13 coupler goes into the C14 inlet on the PSU
Into the PDU	The C14 plug goes into a C13 outlet on the PDU
C14	Inlet on the server PSU, and the plug end of the jumper
C13	Coupler on the jumper, and the outlet on the PDU
Current class	10 A class. Not a 16 A C19/C20 feed

When you need C19 instead

Look at the inlet on the PSU, not at the chassis name. If that inlet is C20, the cord is a C19–C20 jumper: C19 into the server, C20 into a PDU C19 outlet. A C13–C14 cord does not mate with a C20 inlet. See C19 vs C20.

How to remember it

The number on the inlet is even (C14, C20). The number on the cord coupler is odd (C13, C19). A C13 cord goes into a C14 inlet.

One server and one PDU

Dell PowerEdge R650, common PSU inlet C14, with APC AP8941. Schneider lists that PDU as 21 C13 outlets and 3 C19 outlets. The jumper is C13–C14: C13 into the R650, C14 into one of the C13 outlets. Leave the C19 outlets for a PSU that has a C20 inlet.

Worked pair: R650 + AP8941.

Sources

Server: Dell EMC PowerEdge R650 Installation and Service Manual (PDF)

PDU: Schneider Electric APC AP8941, 21 C13 and 3 C19