Small Conductor Usage and Fusing - [NEC 240-3(d)]

[zenon2cubed]

I have a question Regarding NEC 240-3(d):

(d) Small Conductors: Unless specifically permitted in (e) through (g), the overcurrent protection shall not exceed 15 amperes for No. 14, 20 amperes for No. 12, and 30 amperes for No. 10 copper; or 15 amperes for No. 12 and 25 amperes for No. 10 aluminum and copper-clad aluminum after any correction factors for ambient temperature and number of conductors have been applied.


Now, if one were to manufacture an electrical duct heater. To what amperage could one use No. 12 wire?
We currently use THHW 105 Celsius copper wire (90C is rated at 40 amperes) up to 20 amperes.
Would it be possible to use this wire up to 40 amperes when we do not supply fusing in the unit?


Thanks,
Shane

 

[stevenal]

Check the scope, NEC is for installation, not manufacturing. Check with the listing organization (UL for example) for their manufacturing standards.

 

[zenon2cubed]

We build to the UL 1995 Standard which references the NEC for this particular topic.
I realize this kind of situation can be complicated, if someone even knows the contact info of a person/place who can provide answers for this it would be helpful. TIA.

 

[stevenal]

The answer is no, then. Adjustments for temperature and number of conductors can only reduce the allowed ampacities from the basic ampacities you cited above.