Rewiring small cabin and thinking 30 amp and smaller gauge wire is undersize. How do I calculate correct amperage for breaker. Thinking data (wattage) shold be on back of stove. Then what is the calculation, e.g. watts divided by 80% of breaker size?
Understand that: 50-amp = 6 gauge, 40-amp = 8 gauge, 30-amp = 10 gauge.
40a. breaker w/ #8 Cu. for range or oven.
Just a note regarding #6 Cu.
NEC states it's rated at 55a. and allows a 60a. breaker.
But a 50 amp receptacle canít be protected by a 60 overcurrent device therefore the largest overcurrent that can be installed is 50.
(1) Single Receptacle on an Individual Branch Circuit.
A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.
210.3 Rating. Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device. The rating for other than individual branch circuits shall be 15, 20, 30, 40, and 50 amperes. Where conductors of higher ampacity are used for any reason, the ampere rating or setting of the specified overcurrent device shall determine the circuit rating.
We are told that the receptacle must be as large or larger than the branch circuit and also that the overcurrent device be it breaker or fuse will determine the size of the circuit.
Ranges come with cords that are either 40 or 50 amps. Using the 40 amp cord and protecting the circuit with a 40 amp overcurrent device is the smallest allowed for any range, see 210.19(A)(3).