branch circuit conductor and over current protection size of 3.4kw oven

[csutton]

According to table 220-19 note 4 the load of one oven shall be the name plate rating. I have considered this load to be continious and therefore have calculated the size of the branch circuit conductor and over current protection to be 125% of the nameplate value. Thus, I have a 3.4kw oven which equaits to be 14.17 amps@ 240v. Now 125% of this value equals 17.7amps. This is where I became confused. An inspector told me that I cannot supply this load with #12 nm, due to the fact that at 80% #12 nm can only be loaded to 16 amps and also, the over current protection should be at 80% as well and an 20 A breaker is also to small. So, at 17.7amps according to this I need to use 10-3 nm with an 30 amp breaker. Have I not allready satisfied the branch conductor and overcurrent sizing by adding 125% to the name plate value and shouln't I choose the wire size from the 60 deg. collum @100% and overcurrent protection from the breaker rating @100%. Am I interpreting this wrong, if so please explain.

 

[bphgravity]

To start with, there is nothing on the code that requires dwelling cooking equipment to be considered a continuous load. This solves all your issues.

However, I believe you are correct on your calculation.

Nameplate is 14.17 amperes. Conductors and overcurrent protection is permitted to be based on that rating. 210.19(A)(3).

Even if you do consider a continuous load, you will be okay. 14.17 x 125% = 17.71 ampers. Per 210.19(A)(1) and 210.20(A), the branch circuit conductors and and overcurrent device is permitted to be based on that rating.

I think your inspector is confused...

 

[LarryFine]

I'd also consider whether a larger range might be installed in the future, and use a traditional 40a circuit, unless the physical space, for example, would make this impossible.