[atc98092]

Can anyone weigh in on the required cable thickness for 32amp+ nema 14-50 charging? My Chinese charger has a TUV approved cable but its only 3*2.5mm²+2*0.5mm² which seems small compared to competitors. Plug head gets up to 130F. Cable right off the plug head gets up to 150F

I believe the wire type has some impact, so I'll quote for THWN, which is I believe a more commonly used cable. The charts show 10 gauge wire is good for 35 amps, with 8 gauge jumping to 50. I used 8 gauge to wire my daughter's 40 amp Juicebox, even thought her PHEV only draws 32 amps max. I believe if you use separate wires within conduit you get a higher rating than using a bundled wire. The advantage to a UF cable is that conduit isn't necessary, and in some cases can be direct buried underground. But with UF 10 gauge is only rated for 30 amps and 8 gauge for 40. The larger the wire size, the greater the difference between the two types of cable capacity. And all these numbers are based on copper wire. Switch to aluminum and the current rating drops even lower.

 

[atc98092]

I have to think that using cable that is too small from the plug back would cause some heat issues

Absolutely correct. Too small a cable increases resistance, which generates heat, which is a bad thing. Oversizing electrical cable never hurts, but it does increase cost, so try not to go overboard.

 

[atc98092]

Thanks a great website/resource. I know the nema 14-50 was done with a new 50 amp breaker and 8 gauge copper wire and the run is only 12 inches off my breaker box.

12 inches is nothing. The 50 amp run to my hot tub was probably close to 50', and it was 8 gauge copper. I can't recall exactly what the tub drew at full power, but it did require a 50 amp circuit. You won't have any heating issues with a run that short.