Jerseydaze
Senior Member
ac consensor calls for max 25 amp breaker can I run 12-2 romex ( next size breaker )in this situation?
Residential ac consensor calls for max fuse/breaker?
- Thread starter Jerseydaze
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- New Jersey
- Occupation
- Journeyman Electrician
As JLJ stated the conductors are sized to the MCA and the next size up rule does not apply. The MaxOCPD is not relevant to sizing the conductors.
Jerseydaze
Senior Member
I know this is the rule but what protects the wire from over current?
The overload protection required by 440.52, often integral with the unit, protects the conductor from overload. The OCPD protects against short circuit and fault.
Last edited:
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
True, I might add that if the MOCP is 25 amp, it is possible that the MCA could be low enough that even #14 could be used, even at the 60 degree rating.
Note to the O.P., as others said, the key for conductor sizing in this application is the MCA value. It already has everything figured into it, including the 125%, so you can simply select the conductor size based on the ampacity table using the MCA. Of course you have to be compliant with any ampacity adjustments and terminal temperature.
For example, you could use #14 NM cable for a unit with an MCA of 14.9 and a breaker of 25 amp (if that is the MOCP stated on the data plate. For what it is worth, I've seen more than 1 inspector that does not understand this.
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