A branch circuit is a portion of an electrical wiring system that extends from the final overcurrent protection device (such as a circuit breaker or fuse) to the outlets, lights, or appliances it serves. It is essentially the path that delivers electrical power from the electrical panel to individual devices or receptacles within a building.

In simple terms, a branch circuit is the home run from the circuit breaker to the house's first device containing an outlet or a switch.

Branch circuits can be dedicated to a specific appliance or general-purpose outlets and lighting in residential, commercial, or industrial settings.

Other types of circuits that are not branch circuits are feeder circuits (carrying power from the main service to a subpanel) and service circuits (carrying power from the utility’s power supply to the main electrical panel).

Elements of a Branch Circuit

The key elements of a branch circuit typically include:

1. Circuit Breaker or Fuse: This is the overcurrent protection device located in the electrical panel, designed to interrupt the flow of electricity if there is an overload or short circuit.

A circuit breaker is a switch that automatically trips and cuts off the power when the circuit draws more current than it is designed to handle, protecting the wiring and devices from damage. A fuse performs the same role by melting when it overheats, thus breaking the circuit.

        2. Wiring (Conductors): The electrical wires that carry current from the electrical panel to the outlets, lights, or appliances. These wires usually include:

• Hot wire (typically black or red): Carries the electrical current to the device.
• Neutral wire (typically white): Completes the electrical circuit by returning current to the source.
• Ground wire (typically bare or green): Provides a safe path for electrical current in case of a fault.

         3. Outlets or Receptacles: The points where devices or appliances are connected to the branch circuit to access electrical power. There is a variety of electrical outlets. Different types of outlets (standard, GFCI, AFCI, 240V, etc.) serve different purposes, like protecting against ground faults in wet areas or providing higher power for large appliances.

         4. Switches: Devices that control the flow of electricity to certain parts of the circuit, such as lights or other fixtures. There are single-pole, three-way, and four-way switches depending on the complexity of the control required for the circuit.

         5. Appliances or Fixtures: The end-use devices connected to the branch circuit, such as lights, fans, or kitchen appliances. Branch circuits can serve general-purpose outlets or be dedicated to specific heavy-load appliances (like a water heater or air conditioning unit).

         6. Junction Boxes: Enclosures that protect wire connections and provide a location where circuits can branch off to other parts of the building. Junction boxes protect wire connections from damage, dust, and moisture and prevent electrical shock or fire. They also ensure that wire splicing is safely housed and easily accessible for future maintenance.

Types of Branch Circuits

Common branch circuit types are categorized based on their purpose and the type of electrical load they serve. Here are the most typical branch circuit types found in homes and commercial buildings:

• Purpose: Supplies power to general outlets and lighting in a home or building.
• Application: Used for everyday items like lamps, TVs, computers, and small kitchen appliances.
• Example: A 15- or 20-amp circuit for regular electrical outlets throughout a home.
• Cables: NM-B cables. For outdoor circuits, UF-B cables. 14/2 wire gauge for 15-amp circuits and 12/2 wire gauge for 20-amp circuits.

• Purpose: Dedicated to powering specific appliances that require more electricity than typical outlets provide.
• Application: Large kitchen appliances like refrigerators, microwaves, dishwashers, and laundry machines.
• Example: A 20-amp circuit for a kitchen appliance, such as a refrigerator.
• Cables: Commonly 12/2 NM-B or 10/2 MC metal-clad

• Purpose: Supplies electricity to a single appliance or device that needs its own circuit due to high power demands.
• Application: Devices like ovens, dryers, air conditioners, or water heaters.
• Example: A 30- to 50-amp circuit for an electric range or clothes dryer.
• Cables: Service Entrance Cable (SER Cable) (8/3 or 6/3) or Metal-Clad (MC) Cable

• Purpose: Supplies power exclusively to lighting fixtures.
• Application: Lights in rooms, hallways, and other areas.
• Example: A 15-amp circuit for all the living room or hallway light fixtures.
• Cables: Romex NM-B (typically 14/2 or 12/2 wire gauge for 15-amp or 20-amp circuits)

• Purpose: Used in specialized environments, such as medical facilities or data centres, to supply power to critical equipment that cannot be interrupted.
• Application: Medical devices, servers, or other critical equipment that needs constant, stable power.
• Example: Hospital-grade circuits for life-support equipment.
• Cables: Depending on the type of critical equipment. Can be hospital-grade metal-clad (MC) Cable or shielded power cables.

Cables for Branch Circuits

Here is the list of the common cables used in branch circuits, broken down by residential, commercial, or industrial use:

These cables are used for homes and small residential buildings where wiring is usually hidden inside walls or ceilings.

• Non-Metallic Sheathed Cable (NM Cable)
• Use: Interior wiring for lighting, general-purpose outlets, and appliances in dry, protected areas.
• Application: Walls, floors, ceilings in homes, and residential buildings.
• Underground Feeder Cable (UF Cable)
• Use: Outdoor and underground wiring for lighting, garages, sheds, and outbuildings.
• Application: Wet or damp locations such as outdoor lighting or running power to outdoor structures.
• Service Entrance Cable (SER Cable)
• Use: Branch circuits that carry higher loads for large appliances like ovens, dryers, or subpanels.
• Application: Residential applications that need higher amperage circuits like electric stoves, air conditioning units, or feeding subpanels.
• Thermoplastic High-Heat-Resistant Nylon-Coated (THHN) Wires
• Use: Typically used in conduit for interior wiring.
• Application: Wiring for household appliances and outlets when run inside conduit.

Commercial wiring often needs to meet higher demands due to the variety of equipment and safety regulations in businesses and offices.

• Metal-Clad Cable (MC Cable)
• Use: Commercial wiring for outlets, lighting, and appliances in areas where extra mechanical protection is needed.
• Application: Office buildings, retail spaces, and large commercial installations. Suitable for exposed or unprotected areas.
• Thermoplastic High-Heat-Resistant Nylon-Coated (THHN/THWN) Wires
• Use: Common for pulling through conduits in commercial settings.
• Application: Raceways and conduits in offices.
• Underground Feeder Cable (UF Cable)
• Use: Outdoor or underground commercial wiring.
• Application: Underground wiring for signage, outdoor lighting, and other external connections.

Industrial wiring requires robust cables for high-power machinery and hazardous conditions.

• Metal-Clad Cable (MC Cable)
• Use: Industrial applications for power distribution and branch circuits.
• Application: Factories, warehouses, and industrial plants, especially where the wiring may be subject to environmental wear or physical damage.
• Thermoplastic High-Heat-Resistant Nylon-Coated (THHN/THWN) Wires
• Use: Industrial environments where wires are pulled through conduits.
• Application: High-heat, wet, or harsh industrial environments for power circuits, lighting, and motor connections.

All high-quality cables for branch circuits are available at Nassau National Cable at excellent prices.