You're getting closer to understanding the code, but there are still some crucial distinctions to make. Let's break down why your initial idea (tapping 14 AWG from 12 AWG in a general junction box for lighting) is generally NOT code-compliant, and how 410.117(C) potentially allows for something similar in very specific circumstances.

Why your initial idea is generally NOT compliant (and the key principle)



Overcurrent Protection

The fundamental rule of electrical wiring is that the overcurrent protection device (circuit breaker or fuse) must protect the smallest conductor in the circuit. If you have a 15-amp breaker protecting a circuit wired with 12 AWG, that breaker is designed to protect that 12 AWG wire from overheating. If you tap 14 AWG wire onto that circuit, the 15-amp breaker is not adequate to protect the 14 AWG wire (which is rated for 15 amps, technically, but generally not allowed on a 15 amp circuit, and definitely not on a 20 amp circuit).

In general, you cannot reduce wire gauge (ampacity) without changing the overcurrent protection to match the smaller wire.NEC 410.117(C) - The exception that proves the rule, and VERY specific

This section addresses the very limited situation of wiring directly from a luminaire outlet box (the box where the light fixture itself is mounted) to the luminaire itself.

Luminaire Outlet Box

This means the box specifically intended for the light fixture to be mounted to. This is not a general-purpose junction box located anywhere in the wall or ceiling.

Purpose

This exception is designed to address the challenge of getting wires from the outlet box to the light fixture itself, especially with some fixtures having tight wiring compartments.

Specific Requirements



Temperature Rating

The tap conductors must have insulation rated for the temperature inside the luminaire housing (often higher than standard NM cable).

Cable Type

The tap conductors must be Type AC (armored cable) or Type MC (metal-clad cable).

This is the critical point! Romex (NM cable) is NOT permitted under this exception. Minimum Length

The tap conductor must start within the luminaire or luminaire mounting area, and extends at least 1 foot outside of the luminaire.

Maximum Length

The tap conductor cannot exceed 6 feet in length from the outlet box.

Overcurrent Protection

The original overcurrent protection (e.g., the 15-amp or 20-amp breaker) must protect the branch circuit feeding the luminaire outlet box. This is okay because the tap is only feeding the luminaire itself. It's not intended to supply any other outlets or fixtures.

Why you can't just use Romex (NM cable)



410.117(C) specifically requires AC or MC cable, not NM cable. This is likely due to the need for better physical protection and potentially higher temperature ratings near the luminaire.

In summary

You generally cannot tap a 14 AWG wire from a 12 AWG wire in a standard junction box. 410.117(C) potentially allows the use of AC or MC cable (not NM cable) to run a tap from a luminaire outlet box to the luminaire itself, under very specific conditions (length, temperature rating).

Recommendation:

If you're trying to wire multiple lights from a single circuit, the proper way to do it is to run 12 AWG to each luminaire outlet box. This keeps the entire circuit protected by the 15 or 20-amp breaker, and avoids any code violations. If you truly need to tap down to a smaller gauge wire, you MUST do it in a code-compliant manner (usually with a lower-rated overcurrent device on the smaller wire) or in a very specific circumstance like 410.117(C) using the correct materials.Always consult your local electrical inspector before performing any electrical work.* They can provide guidance on code compliance specific to your area and situation. Electrical work can be dangerous if not done correctly. Flag for review