Ignoramus26750 wrote:

On Thu, 10 Nov 2005 09:36:44 -0800, Esther & Fester Bestertester wrote:

NEC reference says that 12ga THHN wire can carry 30A max
current. Motor load is currently drawing constant 20A (230v
1ph circuit). Breaker is 30A.


It is my understanding that wire must be matched to the breaker. So,
if the breaker is 30A, the wire should be rated for 30A as well. That
means 10 gauge.

NO, not according to NEC and wiring protection practices. You size the
breaker to be 80% of the rated FLA of the conductor. You are protecting
the wire with the breaker, not the motor...If the wiring overheats you
got a fire.
John

i


(A bit of history: Previous motor (running from 208v) was
drawing less (15A?) current until machine broke. New
machine's motor (running from 230v via boost
autotransformer) is drawing 20A (measured at breaker).
Motor spec plate says 16A.)

Is 12ga wire sufficient, or should I bump it up to 10ga?

Would the autotransformer account for the increased current
draw?

FBt