Modernized Engine Wiring

BillGrissom said

A final comment on conductor sizing. Many people think 12 awg = 20 A max, from their knowledge of home wiring. That rating is for wires buried in fiberglass insulation, and the concerns of burning down a house. In a car, the "appliance rating" is more relevant. I recall that is more like 40 A for 12 awg.

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This thread is full of cool information, however I think this is incorrect. Please correct me if I am wrong:

Watts = Volts x Amps

A house circuit provides ~120volts. The wiring on a 12g wire in home use supports a 20a breaker (or load).

Watts = 120 x 20
Watts = 2400 allowed

In a automotive circuit, the system runs on 12v. A 12g wire supports 2400 watts.

2400w = 12v x A

A = 200

Therefore a 12g wire in a car can support 200amps.

Grant