Components

• A branch circuit can have several components. All branch circuits include a power source, a protection device, a pathway for the electricity, and some form of output device. Some circuits include switches to control the output device, such as a light and a light switch.
  
  

Types

• Branch circuits are identified by circuit protection size and type. Common residential branch circuits are 15 amperes, 20 amps, 30 amps, 40 amps, 50 amps, and 60 amps. In a home, the basic circuits are 15 amps. They supply power to receptacles and light fixtures. The remaining circuits power specific appliances. In businesses, the basic circuit is 20 amps.
  
  

History

• In the early days, branch circuits used paper insulation in the electrical wiring. This caused problems if that cable became wet. These circuits were not designed to carry a lot of power. This is why many old homes have wiring problems if too many devices are used on old wiring. Many times the old cable is undersize for the amount of current and power it is trying to carry.
  
  Today the National Electric Code dictates how homes and businesses must be wired. This helps to reduce the number of fires caused by improper and defective wiring.
  
  

Warning

• Branch circuits carry a lot of power, and extreme care should be used when working around them. A branch circuit in a home operates at 120 volts or 240 volts. The minimum current carried by these circuits is 15 amps. This is more than enough to kill a person in less than a second.
  
  If work must be done around a branch circuit, know where the circuit is, where it goes, what it supplies power to, and whether or not it is in danger of being damaged.
  
  

Benefits

• The power coming into an average home today is a 240-volt, 200-amp line. Branch circuits allow this power to be divided and sent where needed. By varying the wire size, more current can be sent to appliances that require more power. The breakers in the power panel protect each branch circuit from trying to carry more current than the circuit was designed for.
  
  Arc fault breakers are another type used in power panels. These breakers use electronics to monitor the current. They recognize unstable current conditions that could indicate an arc fault. Arc faults can generate excessive heat and sparks in a branch circuit, which could start a fire.