OCP for AC?

[SouthernStateElectrician]

In Mike Holts study guide is has the question:
What size branch circuit over current device is required for an air conditioner (18A), when the
name plate indicates the min ckt ampacity is 23A, with the max OCP of 40A?
Answe given is #12 AWG, 40A protection
I understand how the answer was determined but doesn't that conflict with 240.4 and if it
doesn't can someone help me understand why not? ALSO, is the given answer able to be applied practically in the field. I just can't imagine an inspector being ok with it like that...very curious.

 

[Dennis Alwon]

Look at 240.4(G). This allows 14 awg to be used at 20 amps assuming 75C terminations and wire. The OCPD is allowed to be higher based on 440..22. The a/c has built in overload protection which will protect the conductors so the OCPD is for ground fault and short circuit protection only.

 

[kwired]

240.4(G) sends you to art 440 parts III and IV for this specific application.

 

[jxofaltrds]

In Mike Holts study guide is has the question:
What size branch circuit over current device is required for an air conditioner (18A), when the
name plate indicates the min ckt ampacity is 23A, with the max OCP of 40A?
Answe given is #12 AWG, 40A protection
I understand how the answer was determined but doesn't that conflict with 240.4 and if it
doesn't can someone help me understand why not? ALSO, is the given answer able to be applied practically in the field. I just can't imagine an inspector being ok with it like that...very curious.

Inspectors "OK" this everyday!

 

[Strife]

In Mike Holts study guide is has the question:
What size branch circuit over current device is required for an air conditioner (18A), when the
name plate indicates the min ckt ampacity is 23A, with the max OCP of 40A?
Answe given is #12 AWG, 40A protection
I understand how the answer was determined but doesn't that conflict with 240.4 and if it
doesn't can someone help me understand why not? ALSO, is the given answer able to be applied practically in the field. I just can't imagine an inspector being ok with it like that...very curious.

That is one tricky question.
My first reaction was as yours.
But then it got me thinking:
240.4.D states OCPD should not exceed 15 for #14, 20 for #12, 30 for #10. Unless SPECIFICALLY permitted in 240.4.E or 240.4.G
240.4.G narrative sends you to 240.4.(G) table.
And 240.4.(G) table sends you to 400 part 3 and 6.
And I'm not gonna write down what 400 part 3 and 4 states, but it basically allow what you mention.
The tricky part is our conditioning. Most of people confuse OCPD with ampacity(hey, if OCPD can only be 20A that must be the ampacity). It'd take me years to tell all the stories I had explaining people that the end of the wire is not the middle of it. But even I fell for it for about 5 seconds.