Can i connect 14-2 wire to 12-2 wire

There are a few situations one might see the need to use 14/2 wire with 12/2 on the same circuit. Many times it is a good money saving option if you have a lot of lights to wire but the switch box is fed with 12/2. Also a lot of people prefer working with 14/2. It fits in boxes better, is easier to manipulate and work with etc. Some light housings just provide so little wire space that running 14/2 instead of 12/2 is the difference between a hard work day and light work but is it okay to run 14/2 on a 12/2 circuit?

Yes, it is okay to use 14/2 wire with 12/2 wire on the same circuit. You will have to make sure the 12/2 is fed from a 15amp breaker however. You must size your breaker to the smallest size wire in the circuit. This will prevent overheating of the 14 gauge wires which are only rated for 15amps from over heating and causing a potential fire.

There are however some risks involved that you should consider if it is worth running 14/2 on a 12/2 circuit. It is not so cut and dry.

Is 12/2 landed on the panel on a 20 amp breaker?

If 12/2 which is rated for 20 amps according to NEC code, (see this PDF for illustration) is landed on your panel and you change the existing 20 amp breaker to 15 amps, who is to say someone won’t come along later and change it to 20 amps?

Side note: On the table and in the code book on table 310.15(b)16 it says that 12awg copper wire is rated for 25 amps. If you look at the 2 asterisks ** however it sends you to 240.4(D) which specifies that #12 AWG should only be on a 20amp breaker.

For this reason it is good practice to label the #12 inside the panel as “ran to #14 lights, do not increase breaker size” or something of that nature. The best practice would be running #14 from the panel so the next electrician servicing the house will not be tempted to up the breaker size to 20 amps when they see #12 wire and the customer tells them that the circuit breaker keeps tripping.

Reasons to consider running 14/2 on 12/2 circuit

Money – 14/2 isa bit cheaper. If it is a job with a lot of lighting,consider running 14/2 feeds directly to switches just for safety.

Easy to install – 14/2 is much easier in today’s modern sleek lighting fixtures with the sometimes tiny junction boxes that they come with.

You have it in the van – Seriously, if you have left over 14/2 from another job go ahead and use it. It is code compliant on a 12/2 circuit. Remember the code is the MINUMUM requirement so use your best judgement and take precautions for the next electrician or DIY homeowner who may not be so savvy with wiring as one might thing.

Final thoughts

So yes it is fine if you must use 14/2 wire on a circuit fed by 12/2 as long as it is on a 15 amp breaker. It is also fine to run all your general outlets in a home on one single feed. Is it good practice? NO. Will the next homeowner hate you for it? Probably.

Always keep safety in mind and if at all possible run the 14/2 directly from the panel instead of jumping from the switch.