Multiwire branch circuits wrapper
Why you care (60 seconds)
MWBCs can save copper but create safety risks if neutral continuity or disconnecting means are mishandled. Inspectors check these closely.
Where people lose time
- Missing handle ties or common disconnect requirements.
- Incorrect neutral connections that open the neutral under load.
- Mixing circuits without confirming they share a common neutral properly.
This is
The rule in plain language
A multiwire branch circuit shares a neutral between two or more ungrounded conductors, and it must be wired and disconnected correctly to stay safe.
When it applies
Any time two or more branch circuits share a neutral conductor.
What you must do (checklist)
- Ensure ungrounded conductors are on opposite phases.
- Provide the required simultaneous disconnecting means.
- Maintain neutral continuity at devices and splices.
- Identify MWBCs at panels and junctions.
Quick examples
- A shared neutral requires a common disconnect for the ungrounded conductors.
- A loose neutral on an MWBC can create overvoltage on loads.
This is not
Common misreads
- Treating MWBCs like two independent circuits.
- Assuming any two circuits can share a neutral.
What it doesn't cover
- Detailed load balancing or harmonic concerns.
- Specialty MWBC rules in industrial systems.
False friends
- A shared neutral without a common disconnect is not compliant.
Exceptions & edge cases
- Certain systems require additional identification or protection.
- Some wiring methods need extra neutral handling steps.
Cross-references (NEC map)
- Primary: 210.4
- Secondary: 300.13, 210.7
Exam traps
- Missing that MWBCs require a common disconnecting means.
- Ignoring neutral continuity rules at devices.
Field notes
- Use a checklist at panel terminations for MWBC requirements.
- Label shared neutrals clearly to avoid future mistakes.
AHJ / Local amendments notes (placeholder)
- Add local amendments or interpretations here.
Revision notes
- Draft wrapper created for MWBC fundamentals.