Mike Dolt Enterprises
Mike Dolt Enterprises
User: Will Wire, Location: California: NEC 2020
Asked on: Thursday, January 30, 2025 at 12:51 pm EST
Answered on: Thursday, March 6, 2025 at 8:02 am EST
Question: Situation: Service call on existing house.Branch circuit home runs for lighting 12-2 Romex, 20 amp breakers. Switch legs up to lights 14-2 Romex. My understanding is that this is not code compliant, and that the breaker must be changed to 15 amp, because of the limitation restrictions for small wires in NEC 240.4(D).Am I correct in my understanding?Thanks
Yes, you are correct. Your understanding aligns with the NEC (National Electrical Code) requirements. Here's the breakdown and why: NEC 240.4(D) - Protection of Flexible Cords, Flexible Cables, and Fixture Wires
This section, often referred to as the "small conductor rule," states that conductors size 14 AWG to 10 AWG must be protected against overcurrent in accordance with their ampacities as specified in Section 310.15. More specifically: 14 AWG copper: 15 amps 12 AWG copper: 20 amps 10 AWG copper: 30 amps
The Problem
You have a 20-amp breaker protecting a circuit that includes 14 AWG wire (the switch leg). Because the 14 AWG has an ampacity of only 15 amps, the 20 amp breaker will NOT provide overcurrent protection and is a fire hazard.
Solution
The breaker needs to be reduced to 15 amps to protect the 14 AWG wire.
Therefore, you are correct, the 20-amp breaker on a circuit with a 14 AWG switch leg is a code violation. The corrective action is to replace the 20-amp breaker with a 15-amp breaker. Flag for review