I recently purchased a 1970s era home with the original wiring. The garage has two entrances, neither of which had an opener nor power running up to where an opener would be. I just had new doors and openers (Chamberlain B550) installed and have been running an extension cord up there for a while. Today I got adventurous to run a more permanent solution. I have already mounted outlets and run 14/2 nm-b cable across the ceiling of the garage and only had to run it a few feet down the side of the wall to the outlet. That's where I ran into an issue.

It is on a 20 amp breaker (which I didn't look at before buying 14/2 cable, I not know I should have gone with 12/2) and the only thing I can find on that circuit is that single outlet in the garage and the garage lights (which I've replaced with two 14 watt LED strips). So all in all it's a pretty light load on that

The outlet is only a few feet from the breaker and has a 12/2 cable leading in and out, which I suspect is running to the lights. I was going to pigtail the cable I just ran in to a new 15 amp GCFI outlet when I noticed that it was 12g and not 14g. I know I shouldn't add 14 ga to a 20 amp circuit, so now I'm left either rerunning new cable or downgrading the breaker.

Nothing is ever really plugged into that outlet. There is another 15 amp outlet on a different 20 amp circuit already if I need to plug in anything heavy duty ( I know I need to replace that too). So my real question is if there is anything I should worry about if I did replace the breaker? I don't see it tripping since it is a pretty small circuit and there isn't much load on it. Would it be safe to run it on a 20 amp breaker for a few days until I can go buy a new breaker?

 

The only real issue is that later on in life somebody could see the #12 in the panel and think it is Ok to return it back to a 20 amp breaker. Down grading the breaker to a 15amp is acceptable, but you may want to put a tag on the wire stating that there is #14 on the circuit and should only be on a 15 amp breaker max.

Since the panel is close you could just make a splice in the box you ran the new cable to and then run another cable to the panel (IF the box is big enough).

I would just keep using the extension cords for now.

 

Thanks. There are no markings in the breaker box other than what I've put trying to identify circuits. I think its going to be easier to swap the breaker than run a new line.

 

Put a short 14 gauge jumper (pigtail) between the incoming end of the 12 gauge branch circuit cable black conductor and the 15 amp breaker terminal.