I have to add some floodlights to our detached garage. The whole garage is on a 20 amp breaker. However, I see a lot of 14-2 G and some 14-3 G cabling in the garage. The garage is unfinished so all the cabling is exposed. Is it not inconsistent to have the 14 gauge wiring with a 20 amp breaker? Can this cause trouble?

 

14 gauge wire should NOT be on a 20 amp breaker for a general purpose circuit. Under heavy loads the wire will overheat before the breaker trips. Change the breaker to a 15 amp or upgrade all the wiring to 12 gauge.

 

If the original electricians (1994) had consistently used 12 gauge to the wall outlets and only used 14 gauge to the lights in the garage and the outside spotlights, would we then be okay? I see some 12 gauge to the GFCI and other outlets (these are Essex cables) and not all have readable markings, but I do not know what they used to the garage door openers. We have not had problems in the garage in the four years we have been here, but we do not have heavy equipment such as a wood shop in the garage.

 

The important thing is that the breaker is properly sized to the wire. A wire with a breaker that is too high of an ampacity could overheat and potentially cause a fire before the breaker tripped.

 

The first thing to do is to absolutely ascertain which circuit breaker controls power to the various cables. You may be mistaken in thinking that the #14 is on a 20 ampere breaker.

 

I greatly appreciate the timeliness and cogency of the replies I received. Sure enough I did more homework and found that the garage does have both a 15 amp and a 20 amp breaker. So I presume that all 12 gauge is to the plug-in boxes, and all the 14 gauge is to the lights. A spot check to one of the boxes showed this to be true. All the cables are white, so I have to look at the markings on the cable to see the gauge. Thank you.