I am a definite novice at wiring but I wanted to put up a can light in the finished part of our basement. When I went to Lowe's they said a 14/2 gauge wire should be connected to a 15 amp fuse in the circuit breaker panel. However the lights and all the wall outlets in the finished part of the basement are connected to a 20 amp fuse. Now the outlets do have a 12 gauge wire, but all the wiring for the lights is 14/2 wire. Will it be OK to connect my switch using this 14 gauge wire? Is this wiring situation common where lights just have 14 and outlets 12 gauge wire all connected somehow to the same 20 amp fuse in the fuse box?

Thanks for your help.

re: Wiring up a can light	Warren Goodrich	12:17 pm wednesday september 19, 2001

The NEC allows you to install larger wires on smaller amp rated breakers rated in amps lower than the ampacity of your conductors. The NEC forbids you to install smaller wires on larger amprated breakers rated in amps higher than the ampacity of your conductors.

This means that the breaker or fuse must be rated in amps equal to and must not be higher amp rated than the smallest wire on that circuit.

12 awg cu. wire is rated in ampacity of 20 amps for all wiring designs other than motors.
14 awg cu. wire is rated in ampacity of 15 amps for all wiring designs other than motors.

Therefore if you have a branch circuit that has both 12 awg and 14 awg conductors in the wiring design of that one branch circuit then you must size the overcurrent device protecting that branch circuit in amp rating equal to the smallest conductor in the branch circuit being 14 awg. therefore a 15 amp breaker or fuse is the maximum overcurrent device allowed to protect that branch circuit with 14 awg in that branch circuit's wiring design.

This is true no matter whether this is a single light fixture or switch leg. If there is 14 awg wire in that 12 awg branch circuit then you have a 15 amp rated circuit.

There is an exception considering light fixtures where a tap 1/3 the ampacity of the original branch circuit is allowed to be tapped off that larger branch circuit. The limitation of this light fixture tap rule is 18" maximum length. Switch legs or lighting runs are longer than 18" therefore the tap rule can not be used.

Code references are 240-3 ampacity of smaller conductors 14 awg through 10 awg. 210-19-D taps not over 18".

Hope this helps

Wg

re: Wiring up a can light.	dan	4:12 pm wednesday september 19, 2001

Thanks for the info.

I am still a little confused though. Does this mean since I have a 20 amp fuse connecting both the 14 and 12 gauge wire, I have another branch or breaker somewhere that protects the 14 gauge wire or is my circuit breaker actually a 15 amp circuit breaker labeled incorrectly as 20 amps? or does the fact that any part of the wire is 14 gauge wire automatically make the circuit a 15 amp rated circuit no matter what it says on the box?

re: Wiring up a can light.	wirenuts	5:16 pm wednesday september 19, 2001

Dan;

the breaker needs to be the 'weak link' in the chain. If there is any #14, then it must be energized ONLY via a 15 A breaker. This is the short sweet version, there are exceptions as Warren stated, but for what i'm reading and your purposes you must get a 15A breaker, it will not 'automatically' reduce it's fault level.

re: Wiring up a can light	Warren Goodrich	9:28 pm wednesday september 19, 2001

As Wirenuts says. Your 20 amp breaker must be changed to a 15 amp breaker if you have any 14 awg wire in that circuit at all.

The 20 amp breaker has too high of an amp rating to protect that 14 awg wire that has a maximum amp rating of 15 amps in the wiring system you have.

Good Luck

Wg

re: Wiring up a can light.	dan	12:37 pm monday september 24, 2001

Thanks for your help. I do have one other questions. I have tapped power from a middle of the run outlet to get power to my can light and switch. The actual wall outlet looks like all the connections were push in connections so I took the 14 gauge wire I have and attached it to the screw on terminals that were not being used to get power (black to black, white to white and hooked up the ground). Is there any problem in doing this?

re: Wiring up a can light	Warren Goodrich	8:56 am wednesday september 26, 2001

No there is no problem with using those empty screws on that receptacle when your other wires are using the back stab connection of that same receptacle. However keep in mind that the back stab connections have a history of coming back to haunt you due to loose connections caused by the springs deteriating in their tension capabilities if heavily used with power. 14 awg 15 amp loads usually don't cause the problem. 12 awg with 20 amp resistant loads such as toasters, portable heaters may cause this loose connection problem to appear. Just keep that in mind if you start having intermittent power loss in the future. This can happen at any back stab receptacles throughout the home. Just a bit of history.

good luck

Wg