A multi wire branch circuit in a residential dwelling contains two 120v wires of different phases a and b phase and share one neutral wire as return currentwhen a three wire nm cable is used for this type of circuit. The device can accommodate up to 36 submetering points giving total flexibility for configuration of up to 36 single phase 18 two phase 12 three phase or any combination thereof.
Multiwire Branch Electrical Circuits And Split Wired
Multi branch circuit diagram. This will ensure a balanced load on the neutral. In the diagram above right both phase a and b breakers or switches are open. The red wire is usually the b phase 120v. The multi mon is a multiple branch circuit energy monitor that collects granular energy intelligence data for tenant billing cost allocation and energy management. A multi wire branch circuit is two or more circuits that is served by a a set of hot wires connected to different phases all with the same voltage between them and a common neutral wire all of the hots also have the same voltage with respect to the neutral. There is nothing wrong with using multi branch but if you do decide that it is the best option then make sure you take proper precautions as per code nec 2014.
If instead the electrician made a multi wire branch circuit pair by using positions 10b and 12a in our sketch or from positions 9 and 11 in the sketch using normal full width circuit breakers that would work correctly because the two circuits sharing a common neutral would have pulled power from two different panel bus bars. A common application of multiwire branch circuits as described in section 2104 is for a 120240 volt single phase system where three wires do the work of four the two ungrounded conductors sharing a single neutralin a 20 amp multiwire branch circuit if the two ungrounded conductors each carry 15 amps some people think the neutral carries 30 amps or the combined total of the current on. See multi wire branch circuits and open neutral multi wire circuit for more information. The neutral wire on the left side of the open comes from the panel is 0v. Marvin if the circuit breakers are full size then no this is not correct. By requiring each multi wire branch circuit to be provided with a means to simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates such as at the panelboard or load center a change to 2104b in the 2008 nec prompted the industry to move away from multiwire branch circuits.
A multi wire circuit that shares the same neutral must have each of the two circuits on separate buses and the circuit breakers must be have their handles tied. Rough in electrical wiring national electrical code. As an electrician you can suspect a multi wire branch circuit when three or more neutral conductors are spliced together in a junction box outlet box or lighting fixture. Multi wire branch circuits example one 20 amps home run 123 with ground wire branching into 2 circuits in the kitchen. The black wire is usually the a phase 120v. The wire on the right side of the open goes to the load is also 0v.
This arrangement saves a bit on wire and can also save on conduit fill.
Gallery of Multi Branch Circuit Diagram
