> Because 6 AWG with 90 deg C insulation allows supply up to 75A which is > probably what those public EVSE are designed to support even though they > are connected to 50A breaker and are configured to supply not more than 30 > or 40A (the duty cycle setting of the pilot signal). > > Having a 10 AWG cord allows 40A if the insulation is 90 deg C, otherwise it is > 30A max, see for example the table at > http://en.wikipedia.org/wiki/American_wire_gauge
That table is for one solid wire, not stranded or multiwire conductors. The NEC Table 400.5 (A) and (B) also derate by 20% IIRC, when there are 2 current carrying conductors in the same cable. The J1772 SAE Specs the EVSE cord - "The wiring insulation shall be rated for 105 °C", not 90C. I've got some 105 deg C tables (not NEC) that state that 10 AWG, 2 current carrying conductors, is actually rated at 46.6A. Rush www.TucsonEV.com
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