The Electrical Code

Part II. Branch-Circuit Ratings

210.18 Rating. The down and dirty part of this one is the breaker used needs to be sized to the smallest wire(conductor) in the circuit. Is that simple enough. This way if there is a situation where an over amperage anywhere in that circuit there will be no chance of damage to the wires in the wall where we can’t get to. The draw back to this is if you keep adding to the circuit there will come a time where the breaker will trip in times where it becomes inconvenient or down right frustrating. In these cases the fix is to add another circuit from the panel somewhere in the middle of the circuit that will share the amperage equally by both the new breaker and the old one. Now in the really world that might not be possible but where it is, due to finished walls or the worst is finished basements. In the residential arena of our industry to feed outlets and lights the trick of the trade is to feed with a 15 amp or 20 amp breaker. These breakers need a 14 gauge wire for a 15 amp breaker and 12 gauge wire for a 20 amp breaker. Good luck and if you have any question leave me a comment and I will get back to you as soon as humanly possible and as today is Saturday that’s going to be Monday, hahaha. No really but really as soon as I can, which will be Monday.

“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.

Exception: Multi-outlet branch circuits greater than 50 amperes shall be permitted to supply non-lighting outlet loads on industrial premises where conditions of maintenance and supervision ensure that only qualified persons service the equipment.”