I have an electrical background, but no experience with the electrical code. My wife hired a contractor to remodel the bathroom. When he started connecting 14 gauge wire to 12 gauge circuits, I figured this would be a violation of the code. I challenged him. He called an electrical contractor and said I was wrong. I started researching the code and have composed the following analysis, based on my interpretation. I would very much appreciate some feed-back on what I have concluded.
Scenario: You want to extend or replace a section of wire on a branch circuit. The existing wire in the junction box is 12/2 W/G NM cable.
Question: Can you splice a section of 14/2 W/G NM cable onto these conductors?
First: Determine the rating of the circuit.
Article 210.18 Rating. Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device.
12/2 NM cable is rated for 20A. This would be the maximum rating of this circuit. So, the rating for this branch circuit would depend on the size of breaker at the source; either 20A or 15A. The next step then is to determine the correct value for overcurrent protection.
Article 240.4 Protection of Conductors. Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.14, unless otherwise permitted in 240.4(A) through (G).
For 14/2 and 12/2 NM cable that would be 15A and 20A respectively. The exceptions under 240.4(A) through (G), the next higher standard rating, does not apply because standard breakers are available for 15A and 20A circuits. This, however, does not prohibit protecting the 12/2 NM cable at 15 amperes.
Second: Determine minimum ampacity and size of conductors.
In accordance with Article 210.19(A)(1), the ampacity of the conductors are generally determined by the type and size of the load(s) that they will supply, along with other adjustments.
Article 210.19(A)(2) Branch circuits with more than one receptacle shall use conductors with an ampacity not less than the rating of the branch circuit. So, in this case, if the branch circuit is protected at 20A, then 14/2 NM cable would not be approved for this purpose.
Article 210.19(A)(3) Ranges and cooking appliances shall also use conductors with an ampacity not less than the rating of the branch circuit. Also, taps from these range and cooking appliance circuits shall have an ampacity of not less than 20 amperes. Again, 14/2 NM cable would not be approved in this scenario.
Article 210.19(A)(4) Other Loads. Branch-circuits that supply loads other than those specified in 210.3 (all being fixed loads) and other than cooking appliances as covered in 210.19(A)(3), shall have an ampacity sufficient for the loads served and shall not be smaller than 14 AWG.
Exceptions: Taps with an ampacity of not less than 15 amperes are allowed for circuits rated less than 40 amperes to individual lampholders or luminaires where the taps extend no longer than 18 inches beyond any portion of the lampholder or luminaire.
SUMMARY: If the branch circuit is 12 AWG and protected at 20 amperes, then 14 AWG is not permitted except in the case of supplying power to individual light fixtures or fixed loads as referenced in 210.3. If, on the other hand, the rating of the circuit is downgraded to 15 amperes and the circuit breaker is replaced with a 15 ampere breaker, than receptacles for cord-and-plug-connected portable loads would be allowed. However, to appropriately downgrade the rating of the circuit would require a complete re-evaluation of the circuit; the currently present loads plus the proposed additional loads. It may be that the circuit cannot provide reasonable efficiency of operation while being protected at 15 amperes. If this is the case, then you will not be able to extend the circuit to cord-and-plug-connected portable loads using the 14/2 NM cable.
What I have learned: The code assumes that the state of the circuitry is already compliant with the code. In other words, the rating of the circuits and assignment of overcurrent breakers has been appropriately determined. In addition, the reasoning behind the code, especially in the case of taps, is that as long as ground fault protection, short circuit protection, and overcurrent protection is provided on a circuit to an appropriately configured fixed load, that it is alright to supply this load with a reduced ampacity conductor that is sufficient to trip the breaker.
CONCLUSION:
The bottom line is, there are allowances for splicing 14 AWG to 12 AWG for lighting and fixed loads listed in table 210.3, but for other loads, including receptacles, you might be able to down-grade the breaker in the main panel to 15 amperes if you want to splice 14 AWG to 12 AWG. Otherwise, the answer is no.
RESIDENTIAL REMODEL WORK
(ELECTRICAL CODE QUESTIONS)Scenario: You want to extend or replace a section of wire on a branch circuit. The existing wire in the junction box is 12/2 W/G NM cable.
Question: Can you splice a section of 14/2 W/G NM cable onto these conductors?
First: Determine the rating of the circuit.
Article 210.18 Rating. Branch circuits recognized by this article shall be rated in accordance with the maximum permitted ampere rating or setting of the overcurrent device.
12/2 NM cable is rated for 20A. This would be the maximum rating of this circuit. So, the rating for this branch circuit would depend on the size of breaker at the source; either 20A or 15A. The next step then is to determine the correct value for overcurrent protection.
Article 240.4 Protection of Conductors. Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.14, unless otherwise permitted in 240.4(A) through (G).
For 14/2 and 12/2 NM cable that would be 15A and 20A respectively. The exceptions under 240.4(A) through (G), the next higher standard rating, does not apply because standard breakers are available for 15A and 20A circuits. This, however, does not prohibit protecting the 12/2 NM cable at 15 amperes.
Second: Determine minimum ampacity and size of conductors.
In accordance with Article 210.19(A)(1), the ampacity of the conductors are generally determined by the type and size of the load(s) that they will supply, along with other adjustments.
Article 210.19(A)(2) Branch circuits with more than one receptacle shall use conductors with an ampacity not less than the rating of the branch circuit. So, in this case, if the branch circuit is protected at 20A, then 14/2 NM cable would not be approved for this purpose.
Article 210.19(A)(3) Ranges and cooking appliances shall also use conductors with an ampacity not less than the rating of the branch circuit. Also, taps from these range and cooking appliance circuits shall have an ampacity of not less than 20 amperes. Again, 14/2 NM cable would not be approved in this scenario.
Article 210.19(A)(4) Other Loads. Branch-circuits that supply loads other than those specified in 210.3 (all being fixed loads) and other than cooking appliances as covered in 210.19(A)(3), shall have an ampacity sufficient for the loads served and shall not be smaller than 14 AWG.
Exceptions: Taps with an ampacity of not less than 15 amperes are allowed for circuits rated less than 40 amperes to individual lampholders or luminaires where the taps extend no longer than 18 inches beyond any portion of the lampholder or luminaire.
SUMMARY: If the branch circuit is 12 AWG and protected at 20 amperes, then 14 AWG is not permitted except in the case of supplying power to individual light fixtures or fixed loads as referenced in 210.3. If, on the other hand, the rating of the circuit is downgraded to 15 amperes and the circuit breaker is replaced with a 15 ampere breaker, than receptacles for cord-and-plug-connected portable loads would be allowed. However, to appropriately downgrade the rating of the circuit would require a complete re-evaluation of the circuit; the currently present loads plus the proposed additional loads. It may be that the circuit cannot provide reasonable efficiency of operation while being protected at 15 amperes. If this is the case, then you will not be able to extend the circuit to cord-and-plug-connected portable loads using the 14/2 NM cable.
What I have learned: The code assumes that the state of the circuitry is already compliant with the code. In other words, the rating of the circuits and assignment of overcurrent breakers has been appropriately determined. In addition, the reasoning behind the code, especially in the case of taps, is that as long as ground fault protection, short circuit protection, and overcurrent protection is provided on a circuit to an appropriately configured fixed load, that it is alright to supply this load with a reduced ampacity conductor that is sufficient to trip the breaker.
CONCLUSION:
The bottom line is, there are allowances for splicing 14 AWG to 12 AWG for lighting and fixed loads listed in table 210.3, but for other loads, including receptacles, you might be able to down-grade the breaker in the main panel to 15 amperes if you want to splice 14 AWG to 12 AWG. Otherwise, the answer is no.
