Motor Protection

[Jack33]

Using table 310.16 a 5hp motor requires #8 wire which is good for 50 amps. Using table 430-152 the short circuit and ground fault protection maximun setting is 70 amps. Should this breaker be sized at 250% of the FLC or reduced to 50 amp to protect the wire?

 

[jbt260]

Wire is to be sized for 125% of motor FLA. Assuming motor has overload protection, the breaker should be sized per Table 430.52.

 

[augie47]

Welcome to the Forum.
One has to take a bit for granted in your initial post. Not knowing the voltage/phase charistic of the motor we can only assume your 50 amps is correct. Likewise, the type conductor would dictate if #8 was good for 50 amps (ie: NM is not). The 50/70 numbers don't seem to match NEC.
In general, a 40 amp motor would require a 50 amp wire (40 x 1.25), but would allow a 100 amp breaker (40 x 2.5).
But, as Jack33 states, the conductor, sized per 430.21 is considered to be protected by the motor overcurrent device. The breaker serves as short circuit/ground fault protection and is sized per 430.51. The breaker will quite often be twice the conductor ampacity.