Mobile Site        Sitemap        Copyright © 2016 Electrical101.com. All Rights Reserved.        Terms of Use

Sitemap

Switches | Outlets & Plugs | Ballasts | Replace Ballasts | Troubleshooting | Light Bulbs | Basic Electricity | Save Energy | Misc Articles

Electrical101

Multi-wire Branch Circuits

A multi-wire branch circuit in a residential dwelling contains two 120 V wires of different phases (A and B phase) and share one neutral wire as return current. When a three wire NM cable is used for this type of circuit:

See example diagrams below. Receptacle ground connection diagram shown separately.

Multi-wire Branch Circuit Wiring Diagrams

Multi-wire Branch Circuit Correct Wiring Diagram

Multi-wire Branch Circuit Correct Wiring Diagram Multi-wire Branch Circuit Preferred Wiring Diagram

The neutral wires are connected together before connecting to the terminals on the left receptacle. The NEC does not require the 120 V (black) wires to be connected together before connecting to the terminals on the left receptacle.

It is preferred that the 120 V (black) wires to be connected together before connecting to the terminals on the left receptacle, even though it is not required by the NEC.

Multi-wire Branch Circuit Incorrect Wiring

Multi-wire Branch Circuit Incorrect Wiring

The neutral wires are not connected together before connecting to receptacle on left. The two left receptacles do not meet the NEC for a multi-wire branch circuit. If the neutral wires are disconnected with B phase power turned on, the neutral wire from the B phase receptacle is 120 V.


Home

Basic Electricity

Electrical Voltages

Low Voltage

Electrical Definitions

Ohm’s Law

Electrical Circuits

Multi-wire Branch Circuits

Circuit Current Ratings

NM Cable (Romex®)

Wire Connectors (Wire-nuts)

Multi-wire Branch Circuit Preferred Wiring Diagram