Ampacity different ???

[Toros]

Hi
why ampacity is different here?

thru #12 copper, protected by a 30 fuse I can supply a motor

but for ltg load I need #12 copper thru 20 fuse max

Tanx

 

[GoldDigger]

Hi
why ampacity is different here?

thru #12 copper, protected by a 30 fuse I can supply a motor

but for ltg load I need #12 copper thru 20 fuse max

Tanx

For the motor, the starting current will be higher than the ampacity of #12, but will not damage the wires.
A short circuit will be protected just as well by a 30A as by a 20A.
And long term overload of the wires will be protected by the motor overload device.
In a lighting circuit there is no such separate overload, so the breaker must serve that function too.

 

[don_resqcapt19]

The ampacity of the conductor has not changed, just the overcurrent protection rules are different.