One body, two rulebooks

The facts

The IEC 60309-2 figures come from the dimensional standard that makes bodies interchangeable worldwide. The North American figures come from UL 1682 (plugs, receptacles and cable connectors for industrial use) and CSA C22.2 No. 182.1, which test the same bodies to North American conditions and list them at the NEMA-style ratings.

Why the numbers differ

The two systems size wiring devices differently. IEC ratings step 16, 32, 63, 125; North American practice steps 20, 30, 60, 100. When the pin & sleeve bodies were harmonised, each shell was listed at the nearest figure on each side. The 20 A body is not a heavier 16 A body; it is the 16 A body, listed for 20 A under the North American test regime. The same holds at 30/32, 60/63 and 100/125.

Which figure to design to

The one your inspector reads. On a North American installation the c(UL)us listing governs, so a 320P6W is a 20 A device and the cord behind it is sized for 20 A (12 AWG in SOOW or SJTW is typical). In an IEC installation the same body is a 16 A device and the cable is 1.5 or 2.5 mm² to the local rules. A cord we build for export carries the cable and the marking for the country it ships to.

Never in one breath

A range statement that reads "16 to 100 A" mixes the two systems and is meaningless. Say 16 to 125 A IEC, or 20 to 100 A North American. The clock finder folds an IEC amperage onto its North American body so you land on the right cell whichever figure you typed, and then says which figure it did that with.

The IEC-only bodies

A few bodies exist only in the IEC series (the 125 A five-pole in some hours, for instance). They still show on our clock in the 100 A column, because that is the body, and the cell says whether we build a cord on it.