We are seeing a lot of "mini split" AC units. As an example, let's say we have a mini split with an MCA of 11 amps, and a maximum fuse or circuit breaker of 25 amps per the nameplate. The wiring method is Romex. Wiring the unit with 14/2 would satisfy the MCA, however I believe it would violate 250.122 due to the 25 amp OCPD. To comply with 250.122, using Romex it seems we would need 10/2, no? Am I missing something?

You have to determine the OCP that you are installing to determine the EGC for the circuit.

Using the nameplate MAX of 25 OCP would require #12. This is based on 250.122 table in '11 NEC as I read it.

BigB...The first sentence of 250.122(A) says that in no case shall the EGC be required to be larger than the circuit conductors supplying the equipment...

I use the Minimum Circuit Ampacity to size my branch circuit conductors for an AC unit...

Please note that the 2014 edition will have changes to this requirement in air conditioning article.

Ah so I was missing something. The scary part is I am pretty sure I knew that at one time. Getting old is no fun.

Perhaps a little clearer....

BigB example is 14/2NM, but he said 25 amp OCP, using the nameplate max figure.

Using the max OCP, a #12 EGC would be required, so using NM he has to use 12/2.

Yes, the EGC does not have to be larger than the circuit conductors, 'oversize' EGC to my knowledge is not available.

IMHO, I believe that he did not read Table 250.122 where the amperage col. jumps from 20 amps for #12, and 60 amps for #10.

I agree with the getting old and memory loss...

short:
Ditto!!

I'm not sure I follow you Hotline...

When doing AC units the nameplate has all the info for sizing the branch circuit wiring...and sizing the overcurrent device.

For example...if the nameplate gives a MINIMUM BRANCH CIRCUIT AMPACITY of 30amps and a MAXIMUM BRANCH CIRCUIT OVERCURRENT DEVICE of 50amps...

I will wire the unit with 10-2 romex and connect it to a 50amp breaker.

Follow me?

shortcircuit