definition of multifamily dwelling

[larrywd]

according to Mike Holts NEC exam prep, you may not use table 310.15 (B) (6) to size the service conductors for a duplex because " table 310.15 (B) (6) is only for single family dwellings" but 310.15 (B)(6) says it's for single family, two family and multifamily dwellings, so if a duplex is not a two family dwelling, then what is?
Thanks

 

[jumper]

Here is a photo that might help explain it.

 

[larrywd]

further explanation

further explanation

Thanks Derek,
I understand what you wrote, I am however still trying to reconcile the explanation with the wording of the article. If the intent is to provide table 310.15 (B)(6) for feeders in single family, two family, and multifamily dwellings, and limit it's use for service entrance conductors to only single family, where all the other stiputions apply for voltage and current, then it doesn't read that way. Or my brain is worse off than I thought.

 

[Smart $]

Thanks Derek,
I understand what you wrote, I am however still trying to reconcile the explanation with the wording of the article. If the intent is to provide table 310.15 (B)(6) for feeders in single family, two family, and multifamily dwellings, and limit it's use for service entrance conductors to only single family, where all the other stiputions apply for voltage and current, then it doesn't read that way. Or my brain is worse off than I thought.

Think of it this way... only conductors which supply the entire load of a dwelling unit can be sized per Table310.15(B)(6). If supplying less than the entire load, or more than one dwelling unit, they cannot.

Thus, where a single set of service conductors supply both units of a duplex, they cannot be sized per the table.

 

[George Stolz]

Try this:

 

[Dennis Alwon]

so if a duplex is not a two family dwelling, then what is?
Thanks

IMO a duplex is two single family dwellings.

 

[iwire]

I don't think the NEC uses the word duplex in regards to types of dwelling units.

Dwelling, One-Family. A building that consists solely of
one dwelling unit.

Dwelling, Two-Family. A building that consists solely of
two dwelling units.

Dwelling, Multifamily. A building that contains three or
more dwelling units.

Dwelling Unit. A single unit, providing complete and independent
living facilities for one or more persons, including
permanent provisions for living, sleeping, cooking, and
sanitation.