CLIFFS
I want to add a 20-amp circuit/outlets in my garage b/c there's only one existing 15-amp GFCI outlet in the garage (which is gang-wired with a few other outlets inside the house), and the associated breaker trips when I try to run the table saw and dust collector.
That is normal for GFCI outlets and usually not because of the load but because of the noise induced from the motors causing the GFCI to trip.
Not looking for fancy. I want a simple, surface mount outlet box with the standard shiny metal conduit running from it to the breaker box. Said breaker box is also located in the garage, about 20 feet from where I want the outlet.
Code states outlets must not be more than 6 feet from one outlet to the next , in a non living space like a garage the code doesn't apply UNLESS you make it a living space which using it for a home workshop does. The idea is that whatever your intended usage for the space you shouldn't be more than 6ft from an outlet for whatever you have to power.
I contacted a local licensed/bonded electric contractor and they quoted me $500 for the job. This is a new house (6 years old), BTW. This job requires about $60 in supplies; everyone knows this.
True it will cost more to hire someone, but you are paying for the peace of mind that it is done right and your home will not burn down.
I have changed outlets, installed dimmers, ceiling fans etc before, safely (appropriate gauge wire, grounding etc) but never done something like this before.
Would someone please tell me how to wire a 20-amp breaker into the box and run the wire?
The very first thing you want to do when you start to work is turn off the main service disconnect. This will be the largest breaker in the box and will usually be rated 200 amps. Do not ever open a breaker box without turning off the service disconnect first. That will turn off both phases of the power on both sides of the breaker box. Be careful though because the rails near the very top where the disconnect breaker is located can still be HOT and if you contact them there is
NO DISCONNECT OR SAFETY DEVICE between you and about 4000 amps of current. Most boxes will have those covered by a guard of some sort but not all. Depending on the install you can have one where the power goes from street to meter to breaker box with disconnect or you could have one where it goes street to meter to disconnect in its own box then breaker box. Whichever you have make sure to turn off the disconnect closest to the meter .
After you remove the cover use a meter to verify that the power is off,
don't trust the breaker.
The best way to wire something like a garage is with metal clad and metal boxes. I would do a couple outlets and string the metal clad between each of the boxes making sure to secure the metallic casing of the cable to each box so the ground is on the cable shield and the metal boxes. Using plain romex cable in a garage is against code because it can be snagged or cut by normal day to day task in the garage. I would go with AWG 12 wire due to the load that things like saws have when they first start.
Height requirements for code have changed, outlets are to be 4ft. 6 inches from the floor for a standard outlet and anything below that height has to be child proof. Breakers are recommended to be AFCI type for all new breakers installed, they detect when two wires touch and kill the power. Garages can also be wet locations so that adds the GFCI requirement as well so you would need a ARC Fault + GFCI combination breaker.