Branch circuit, short circuit and ground fault protection for ac motor

[Chuck 1961]

I have a test question that reads no exceptions apply maximum standard size non delay fuse permitted for branch circuit short circuit and ground fault protection for AC motor where given the following: 2 hp- 120 volt single phase, continuous duty, nameplate current rating 22 amps.

Calculations give 72 amp
I chose 80 amps for the protection
The answer sheet said you must go down to 70 in this case
I could not find a reason why to go down in amperage
What is correct?

 

[david luchini]

I have a test question that reads no exceptions apply maximum standard size non delay fuse permitted for branch circuit short circuit and ground fault protection for AC motor where given the following: 2 hp- 120 volt single phase, continuous duty, nameplate current rating 22 amps.

An 80A fuse would be allowed under exception no 1 to Table 430.52.

If "no exceptions apply" then I would say the max size would be 70A.

 

[Chuck 1961]

The right overcurrent protection

The right overcurrent protection

They did use 24 amp as stated in the table
But I understand now after going back and reviewing 430.52(C)1
With no exceptions!

 

[Chuck 1961]

The right overcurrent protection

The right overcurrent protection

Thank you for your help you’ve been quite helpful!