This article provides some basics on how residential wiring is used and connected together. See the information below for tips and tricks on how to install and modify the wires in your home.

Not sure if this is your problem? See the aticle 'Troubleshooting Wiring Problems' and 'Do It Yourself Electrical Repairs' for listings of all the electrical topics.

Most of the information in this article has to do with what you find inside of a box when you remove a device. What are all the wires for? Which ones are hot? Will something stop working if I unhook something? All good questions, the subjects below will address these concerns.

Wiring Basics

For most homes in the United States, the  power is 110/220 volts. You will sometimes see other designations, like 120/240 or 115/230 volts, why is that? Electrical devices are designed to work with a range of power. The reason is that you have both a design voltage and a maximum voltage. Design voltage for most devices is 115/230 volt. Devices can work with plus or minus 10% of those figures. So a typical outlet may have as little as 104 volts going to it and everything will still work fine.

The higher number is the combined total of the two hot legs of power that feed your panel. When have one hot wire, it is hooked to one side of the panel and provides 115 volts +/- of power. When you have two hot wires, the voltage is doubled, 230 volts +/-.

When you work on a box that has cables coming into it. The number of hot wires in the cable, should tell you what type of power you are dealing with. One black wire would normally be 115 volt, a black and a red (usually red, or another color) would mean 230 volt.

Residential wiring will usually only have three colors of wire, plus a bare ground wire. Unfortunately, the use of these wires is not always self explanatory. As an example, a electric hot water tank can be wired with 10-2 w/Ground wire. The white wire will be one of the hot legs for the 240 volt hot water tank (Note: Most codes do not allow for this method any longer.

Working With Electrical Items

Making Joints

Wiring Diagrams

Stripping Wire

Using Wire Nuts

Braiding Ground Wires

Testing Wires

The white can also be a traveler (meaning it is hot sometimes) in a three or four way light switch. Inside the panel the white wire will usually be hooked into the neutral bar. The exception would be when it is uses as a hot lead. Then it would be hooked to a lug on a double pole breaker. Most electricians will put black tape or a black mark on a white wire that is used as a hot lead. Not always, use your voltage tester to verify what is hot.

Usually, black and red wires are hot. The exception to this would be in light switches, where they may or may not be hot depending on the position of the switch. For three and four way switches the white, red or black could be hot depending on the switch positions and the configuration of the wiring.

Confusing? It can be. In the panel the black and red wires are usually hooked to lugs on the breakers. You see some weird things out there, that is why I use the word 'usually' so much. In other words, some people engage in basic house wiring modifications without checking things out first.

The ground wire should never have a load on it. Sometimes it can act as a neutral, such as the hot water tank wiring mentioned above. In the panel the ground wire would either be hooked to the ground bar or the neutral, if it is acting as the neutral.

Why would installing a new circuit breaker be a needed task? Circuit breakers do go bad from time to time. The other scenario would be adding a circuit to your panel. Finally putting the media room in the basement? For whatever reason you will find that this is not that difficult. Your electric panel has more power coming into it than it needs. The circuit breakers control the amount of power that flows into various areas of your home.

Not sure if this is your problem? See the articles 'Troubleshooting Electrical Repairs', 'Fixing Residential Wiring' and 'Basic Wiring for Homeowners' for a complete listing of all the electrical topics.

Before you add a circuit breaker you need to make sure that you want to attempt this type of project. Working with an electrical panel can be dangerous and it may be impossible to completely turn the power off to the panel. There are also code and permit considerations. As a rule a permit would be required before you perform this type of change to your home.

Safety First

Electricity is dangerous and can injure or kill a person if precautions are not taken. Never work on any electrical device, wiring or panel without first shutting the power off.

See the article 'Residential Electrical Safety Tips' for some suggestions on how to shut down the power.

Reasons for Adding a Circuit Breaker

The wire and the electrical devices that you have in your home can only tolerate a certain level of power. Your original electrician has set up a sort of 'trust arrangement'. The breakers are sized for the wiring and loads that you have in a given circuit. He trusts that you won't overload that circuit. Installing a new circuit breaker would be the wise course of action, instead.

Generally a circuit is set up the use a maximum of 80% of a breaker's capacity. When you exceed 100% the breaker will trip as a safety feature. Kind of an electrical policing arrangement. Two causes for a breaker to trip repeatedly. One it has gone bad. The other is that you are overloading it. Either by too many devices or via a short. Read on to see if this repair is something that you want to try.

With that said, there are situations where adding a circuit breaker for a new circuit is not too difficult. You may want to add a few plugs to your basement for a work shop. Your panel has blank spaces in it and the floor joists are open to run the wires through. Even in this situation, it is a fairly big project.

Panel Size

You can do some checking on your own to see if your panel is large enough for an extra load. You can find electrical load calculators on line to help you with this. These will give you a general idea of whether your main breaker is maxed out.

Most panels are able to have a few extra circuits added to them. You can check the load for your panel by using a 'load calculator'. Follow this link, Single Family Dwelling - Electrical Load Calculator, to check your load. Do you have a hundred amp main breaker? Does the calculator say that you only need sixty five amps? Yes, then you can probably safely add another circuit or two. This will involve installing a new circuit breaker.

Local Codes

More issues here. You will probably need to check with your local building department. Permits may be required before beginning any electrical modifications. Yes, they will want fees. How do you think they pay for those cars with the funny license plates. Wiring for a new circuit is not discussed on this website. Sorry, you are into a home improvement subject. The installation of the breaker is similar, but the wiring is another subject.

Installing a New Circuit 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.

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).

See the articles 'Replacing Circuit Breakers', 'Basic Residential Wiring' and 'Troubleshooting Electrical Circuits' for additional information on this topic.

Summary

Installing a new circuit breaker without any of the related problems is not more than a ten minute job. The problem is that you need to determine if it is really the circuit breaker that is the problem. You may have checked things out and realized that you had eighteen items plugged into one outlet. Or you may have found a short. Your poor circuit breaker had been unjustly accused. Rarely, the breaker is the culprit and needs to be replaced.

Did you decide to add some things? Then installing a new circuit breaker is called for. You may have had a loose wire that was difficult to find. Some serious work. Take comfort in this, if it was hard for you, it would have been hard for someone you hired. What do you do now? Hopefully you have someone that will give you a little well earned praise. Bragging is an acceptable alternative.

Your home will have multiple circuit breaker types. As the name implies they break the current for circuits in your home. This would happen for one of two reasons. One the circuit gets overloaded or a short occurs. The breaker will trip before the wire gets too hot. The other would be the ability to manually shut the power off to work on the electric or a device.

Not sure if this is the right place? See the article on 'Basic House Wiring' for information on all the wiring topics. Got an electrical project that you need to get done? See 'Wiring Electrical Fixtures' and 'Home Electrical Repair' for a listing of all the related articles.

Breaker Types

The following is a brief overview of the various circuit breaker types found in most residential homes:

Single Pole Breaker - This breaker works on one side or 'pole' of your 240 volt service. Thus, it controls a 120 volt branch circuit. The amperage can range between 15 and 30 amps with 15 and 20 amps being the most common. This type of breaker will be used for outlets and lights in your home. They can also be used for individual circuits that require 120 volts, such as furnaces, washing machines and sump pumps.

Double Pole Breaker - This circuit breaker type picks up both poles of a 240 volt service. So this type provides 240 volt power to the circuit. They are used for appliances like ranges, ovens, dryers and water heaters. Double pole breakers can go up to 100 amps or more. Higher than fifty amps is usually to feed a sub panel somewhere else in the home.

GFCI Breakers - Ground Fault Circuit Interrupters are for circuits that service areas of your home where water is present. Bathrooms, kitchens, garages and outdoor receptacles all require GFCI protection. This type of circuit is not always opted for, since it can involve an lot of extra wire to pick up the individual wet location devices. GFCI protections can also be achieved by installing protected outlets at key spots.

AFCI Breakers - Arc Fault Circuit Interrupters protect against arcing that can cause fires. Home built since 2008 are required to have arc fault protection for bedrooms and living spaces. These breakers generally have a gray color and a special reset switch on them. The wiring in older homes may not allow for the use of an AFCI Breaker.

Half Size or Mini Breakers - Standard single pole and double pole breakers are available in a half size model by many manufacturers. Standard single pole breakers are 1" thick and a 'Mini' will be 1/2". this a great feature for adding circuits to an existing panel. The panel box must be set up for the use of mini breakers. Some panels do not allow for them or only allow for a certain number.

Adding Circuits

The ability to add circuits to a panel box will depend on a couple of factors. The first would be the load on the panel. Is the main breaker large enough to accommodate another circuit. The second would be available spaces. For a panel that is filled you may be able to purchase half size or mini breakers. You can put two of these in place of one full size breaker. See the article 'Adding a New Circuit Breaker', for more information.

Breakers are usually specific to the panel manufacturer. Some are interchangeable but it best to check and make sure the breakers are compatible with the panel you have. Take one with you to be sure.

Replacing Breakers

Yes, circuit breakers can go bad. They usually fail on the side of tripping when there is no overload. When they go bad, the only option is to replace the breaker.

Another reason to replace a breaker would be to change the type, although this would be uncommon. You could add a GFCI breaker to your panel if wanted to cover a group of plugs with this protection, maybe in your garage as an example.

The two key concerns for replacing a breaker are: First, getting the right one and Second shutting the power to the panel off before you attempt to change the breaker.

For a complete discussion on replacing a breaker, see the article 'How To Replace a Circuit Breaker'. This information will provide step by step information changing out the breaker.

The basic house wiring in homes built in recent decades have copper wire in them. Houses built in the 1970's may have aluminum wire in them. Aluminum wire has been linked to fires and is no longer allowed in most places. If you encounter aluminum wire in your home you may want to have an licensed electrician check it out.

Got an electrical project that you need to do? See the articles 'Home Electrical Repair', 'Residential Wiring Projects' and 'Basic House Wiring' for a listing of do it yourself projects that a homeowner can accomplish.

Wire or Cable?

Sometimes we use these terms interchangebly and there is nothing wrong with that. Technically speaking 'Wire' is the individual strands that are used for various purposes in an electrical installation. Wire can have insulation or be bare. It can also be made of different materials. However, most wire used in residences that is available for purchase is copper.

Wire

Wire comes in several gauges. The gauge of the wire is simply the diameter or a way of specifying how much current it can carry. Wire gauges that you are likely to encounter in your home are sized from 24 to 6. Guage sizes are counterintuitive since the larger the number the smaller the wire is. A wire rated 24 AWG is a very thin wire that you would use on a doorbell or garage door opener. Wire that is rated 6 AWG would be used for an electric range or an central airconditioning condenser.

Common Wire Sizes In Your Home

Amperage for Wire Sizes

16 - 24 gauge low voltage

14 gauge 15 amps 1440 watts (120) volt

12 gauge 20 amps 1920 watts (120) volt | 3840 watts (240) volts

10 gauge 30 amps 2880 watts (120) volt | 5760 watts (240) volts

8 gauge 40 amps 7680 watts (240) volts

6 gauge 55 amps 10560 watts (240) volts

Wire Colors

Bare

Not really a color, but worth mentioning. The bare wire if there is one, is always the ground wire. Inside of 'Romex' or NM-B cable, the ground is bare and it is wrapped with kraft paper.

White

Black, Red, Blue, Orange, Yellow, etc....

Wire Insulation

THHN; THWN

Bare

Wire Types

Solid

Stranded

Cable

Cable generally refers to a group of wires. The wires are not necessarily all the same size and are usually different colors. Cable is shielded with either abmetal or plastic casing. This serves to protect the wires. Inside the cable the individual wires will also have a plastic insulation. Sometimes the ground wire inside of a cable will not have any insulation.

Cables can have different quantities of wires. They can also have different gauges in them. Most of the time when you are talking about wire, you mean a cable that has all the conductors that you need for a particular application.

Shielded cable is usually three or four wires. A designation such as 12-2 w/Ground or 10-3 w/Ground refers to the wire gauge and number of conductors. The first number is the gauge. Standard gauges are #14, #12, #10, #8 and #6. The second number indicates the number of insulated conductors. A "2" would mean a black and white wire. A "3" will likely mean a black, red and white wire. The w/Ground would mean that it has a bare ground wire inside also. Almost all shielded cable, that is sold today, comes with a ground wire in it.

Cable Designations

There are certain designations for cables that tell you what it is used for in general. For residential applications, you will likely run into three different types. The desinations are listed below:

NM-B

NM = Non Metallic, B = Temperature Class (194 deg farenheight). This is probably the most common wire you will find in your home. It is often called 'Romex' and is fairly easy to work with. If you don't have this type already, it is still the type you will most likely use for any upgrades. Originally, NM-B cable was all white, no matter what gauge of wire was inside of it. Now the jacket for the cable is color coded for the conductors that are inside of it, see 'Cable Colors' below.

Installing NM-B Cable

There are some restrictions for installing this type of cable. It is a flexible cable so it needs to be attached to something that provides support. It needs to have approved fasteners within a foot or less of a termination box and every four feet along an otherwise unsupported suface. Running a non metallic sheathed cable through the holes in wood studs counts as support.

NM cable is generally used for wood frame buildings. It cannot be used for metal studs without additonal protection. For wood studs the cable should be kept a minimum of 1 1/4" back from the edge of the stud. If this cannot be done, a metal protection plate needs to be installed.

UF-B

UF = Underground Feeder, B = Temperature Class (194 deg farenheight). This type of cable is a direct burial cable that can be used for outdoor and underground applications. The plastic jacketing is bonded to the wires, creating a tough cable that resists moiture and damage. You would normally use this wire in a wet environment and buried in the ground.

Installing UF-B Cable

MC Cable

MC = Metal Clad Cable, Temperature Class (194 Degrees farenheight). Similar to 'romex' or NM cable, this type can have multiple conductors of various gauges. It can also include a ground wire

AC Cable

NM-B Cable Color

White = 14 ga wire; Yellow = 

Orange

Gray

Black

Using Wire & Cable

The wire you need to use will depend on the situation. For outlets and lights you will use 14-2 or 12-2 w/Ground in most situations. Exceptionally long runs or high amperage devices may require heavier wire. Examples of this might be a sump pump, furnace or refrigerator.

Some 240 volt devices such as a hot water tank or electric base board heaters might use 12-2 or 10-2 w/Ground. Local codes, amps and distance will govern the correct wire size. Ranges and electric ovens require a lot more amps and are usually wired with 8-3 or 6-3 w/Ground. Appliances that are 240 volt but do not use as much amperage, like a dryer can be wired with 10-3 w/ground.

Remember, local codes govern and some areas require installations that are more stringent than national codes. Check with your local building inspector before beginning a project.

Purchasing Wire