A white neutral wire is linked to a GFCI or AFCI breaker. In the electrical panel, this wire is linked to the neutral bar. The neutral wire is linked to the GFCI or AFCI circuit breaker. It should be black with red or white tape in the cable running to the house.
If you're lucky enough to have an electric panel, then there's a good chance that it's fed by single-wire ground cables. In this case, the neutral wire is the only wire in the cable feeding into the panel. It must be white to match the other wires in the cable.
The term "neutral" comes from the word "neutrality". A system is called "neutral" grounded if there is a continuous path for current between any two points in the system. In an electric power system, this means that there cannot be a complete separation of positive and negative charges at any point in the system. If you were to connect a voltmeter to one of these neutrals, you would see that it reads zero volts even when there is a live power line connected to the opposite terminal of the meter. This is because there is still a path for current between both lines, so they can't be considered as separate circuits.
Connect the ground wire from the new cable and the neutral (white) pigtail from the AFCI to the neutral bus on the main panel. Tighten the AFCI neutral pigtail and ground wires to the neutral bus's empty screws. When placing a breaker on a sub-panel, make sure the neutral and ground are on different bus bars. If they're not, then you have a hot conductor on ground which is dangerous if any other circuit on that bus bar gets activated.
The last thing you want is for a breaker on one of these sub-panels to open while another one doesn't. To prevent this from happening, each breaker must be connected to its own neutral bus bar. This means that each time you add a new breaker, it will get its own neutral bus bar. Old breakers won't work with the new system because they're connected to the same bus bar as the old one. This connection should always be done by an electrician who knows what they're doing.
Sub-panels can be useful if you have several groups of circuits that need their own protection. For example, you could have a group of appliance circuits, another group of bathroom or laundry rooms, and a third group for outdoor lighting and equipment. By dividing up the panels this way, each group of circuits can have its own breaker without affecting the rest of the house.
To connect a breaker in a sub-panel: First find the bus bar that goes with the breaker.
The bare aluminum ground wires in the image above connect to the ground bus on the top left. The ground (bare) wires from all circuits leaving the panel (both 110v and 220v) are also linked to this ground bus, as is the neutral wire from 110v runs alone. The majority of residential wiring is copper. Some older homes used aluminum cable because it's lighter weight and more flexible, but most new houses have copper wiring installed by default.
Any metal part of an electrical system can be a source of danger if it comes into contact with live electricity. This includes parts such as cables, circuit boards, metal boxes, and metal appliances like washers and dryers. These sources of danger must be taken out of line with the live circuit before they can be worked on or repaired. The process of taking something off of live power is called de-energizing it.
Tools used for de-energizing metal objects should be non-conductive tools that will not touch any part of the electrical system. These tools include screwdrivers, pry bars, and voltage meters. If you're not sure whether or not you should be using a specific tool on a given circuit, call someone who knows the house better than you do. They'll be able to tell you if it's safe to work on that circuit without shutting it off first.
Shutting off electricity to a home is an important task that needs to be done with care.