When installing a new circuit breaker, the first thing you need to find out is who the manufacturer is. Breakers need to match the panel they are used in. Ideally you would take the name of the manufacturer and the old breaker with you when you go to the supply store. Make sure you get an exact match.
Size does matter when you are installing new circuit breakers. First you need to make sure you get a breaker with the same amperage. Common single pole breakers are 15 and 20 amp. That does not mean a 30 amp single pole is never used. Get a breaker that is the same amperage as the original one.
Are you confused now? Did I forget to explain the single pole, double pole thing. You have two types of breakers in your panel. You guessed it, single pole (120 volt circuits) and double pole (240 volt circuits). Both types can be in several different amperage ratings. To get the sense of it, your outlets and lights will usually be on single pole circuits. Your range and dryer will be on a double pole circuit.
With that said, you want to get a breaker with the 'right number of poles' (What's a pole, anyway?), the right 'amperage' and made by the right manufacturer. Simple, right? Actually it is not that hard. There are not that many manufacturers and the amperages are standard. Installing a new circuit breaker with the wrong breaker will not work.
Oh! I'm sorry, I forgot, there is the physical size of the breaker. To add insult to this, most manufacturers make full size and half size breakers. Usually, 1" for full size and 1/2" for half size (minis as they are often called). So all of the above applies to two different sizes.
Mini breakers are ideal for adding circuits to a panel that is full. Two minis take the place of one full size breaker. Are you faced with this problem? You will have to replace one breaker with two breakers if you are adding to a panel that is full.
Wow, did I say this was easy. Installing a new circuit breaker the right way, takes a little bit of effort. Think it through and you will be fine.
One more issue with the circuit breakers. Newer homes are equipped with arc fault circuit breakers. These are designed to improve safety. They are more expensive and are wired differently that normal breakers. These are required in homes built since 2008 for many circuits in a home. These breakers have a test button, a neutral terminal and an extra wire that goes to the neutral bar. You will need to check with your local building department for arc fault requirements in your area.
Installing the Breaker
A circuit breaker is very similar to a light switch. It interrupts the hot conductor or power conductor. The difference is that a circuit breaker has limits to the amount of power it allows to go through. Remember, the 'electricity police'.
So you really only have two elements for the circuit breaker. The breaker and the slot it goes into. The other element is the hot wire(s) for the circuit. It's really not that simple, but it sounds good. I take that back. Installing a new circuit breaker in a replacement situation is that simple. One wire and the slot.
Almost every circuit has two other elements. The neutral wire and the ground wire. The neutral wire completes the path so the electrons have a loop to go through. Don't ask questions at this point, you won't understand the answers.
The last element is the ground. The ground is a safety feature. If the neutral ever fails the electricity will go to the ground before it goes through your body. Great feature in my opinion. You can liken it to a safety harness on an iron worker. Fifty stories up it is a hassle to put on a harness. As long as he does not slip the harness is never used. One slip and the harness saves his life. Well worth the hassle.
Before you begin installing a new circuit breaker, make sure the main breaker is off. The circuit breakers are friction fit into the panel. Generally you pull up on the side away from the center and they pop out. You hook them in the center, keeping them at an angle and press them into place. How easy is that? The breaker has a lug or lugs on it to hook up the hot wires.
For a single pole circuit it will usually be the black wire. Sometime a red wire if two circuits are being fed with a three conductor cable. Double pole breakers have two lugs. Sometimes a black and a red wire. Sometimes a black and a white. You put the hot wires in the lugs for the breaker. The neutral goes on the neutral bar (mostly white wires attached) and the ground goes into the ground bar (all bare copper wires attached)