Taps.

[robert pitre]

I was asked if I come off my last receptacle from my bedroom with 12/3 to my first smoke alarm than can I use 14/3. I asked what size is the breaker, he told me 20amps. I reply no,code requires breaker is to be to the smallest wire on this branch. My question is this in 240 over current protection? I thought I have read some were in code (breaker have to be size to the smallest wire on that branch), were is this statement located in the NEC? Thanks.

 

[Dennis Alwon]

First off this is not really a tap. Secondly whoever told you this is incorrect. Look at 240.4(D) it's the best I know about. Obviously the weakest link is what determines the max overcurrent protective device except [perhaps in a few cases of motors, etc. The circuit would require a 15 amp ocpd

 

[GoldDigger]

It would only be a tap in the NEC sense if the 14/3 were protected at the downstream end by its own 15A OCPD.

 

[petersonra]

I was asked if I come off my last receptacle from my bedroom with 12/3 to my first smoke alarm than can I use 14/3. I asked what size is the breaker, he told me 20amps. I reply no,code requires breaker is to be to the smallest wire on this branch. My question is this in 240 over current protection? I thought I have read some were in code (breaker have to be size to the smallest wire on that branch), were is this statement located in the NEC? Thanks.

You won't find it because it is not there, at least not as you are phrasing it.

However, take a look at 240.4(D).

 

[Carultch]

I was asked if I come off my last receptacle from my bedroom with 12/3 to my first smoke alarm than can I use 14/3. I asked what size is the breaker, he told me 20amps. I reply no,code requires breaker is to be to the smallest wire on this branch. My question is this in 240 over current protection? I thought I have read some were in code (breaker have to be size to the smallest wire on that branch), were is this statement located in the NEC? Thanks.

An example of a tap, in the NEC definition, would be if you have a 20A circuit with #12 wire, and then you attach a splice to the middle of it, branching a #14 circuit that eventually terminates on its own 15A breaker. The #14 wire is not directly protected at its 15A ampacity until it gets to its own 15A breaker. That portion is protected in excess of 15A, at 20A instead. 20A still provides short circuit protection, just not overload protection. And in some cases, this is acceptable for lengths within specific limits. See 240.21(B) for more detail.