Building Code Glossary
Branch Circuit, Multiwire: Building Code Definition
How the IRC 2009 define branch circuit, multiwire, where the wording differs, and which chapters depend on the term.
On this page
Last updated September 7, 2026 · Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control.
Direct answer
Branch circuit, multiwire is a defined term in the International Residential Code (IRC) 2009, in Electrical Definitions. The code's own words are: “A branch circuit consisting of two or more ungrounded conductors having voltage difference between them, and a grounded conductor having equal voltage difference between it and each ungrounded conductor of the circuit, and that is connected to the neutral or grounded conductor of the system.” No other I-Code in this corpus defines it, so the IRC 2009 definition is the one to work from. The term is used in 4 chapters of this corpus, most often in Branch Circuit and Feeder Requirements (IRC 2009), Services (IRC 2009), General Requirements (IRC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted.
Content and cited inputs reviewed by Scott Barrington, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Branch Circuit, Multiwire — IRC 2009, Electrical Definitions:
A branch circuit consisting of two or more ungrounded conductors having voltage difference between them, and a grounded conductor having equal voltage difference between it and each ungrounded conductor of the circuit, and that is connected to the neutral or grounded conductor of the system.
What must be verified before using this guidance?
Branch Circuit, Multiwire is defined once in this corpus, in the Electrical Definitions chapter of the International Residential Code (IRC) 2009:
A branch circuit consisting of two or more ungrounded conductors having voltage difference between them, and a grounded conductor having equal voltage difference between it and each ungrounded conductor of the circuit, and that is connected to the neutral or grounded conductor of the system.
Where branch circuit, multiwire is used in the code
The term appears in 4 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Branch Circuit and Feeder Requirements | IRC 2009 | 7 |
| Services | IRC 2009 | 4 |
| General Requirements | IRC 2009 | 2 |
| Electrical Definitions | IRC 2009 | 1 |
The term in use
How the code actually writes about branch circuit, multiwire, quoted from the 2009 text hosted here:
Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.
The terms branch circuit, multiwire is built out of
The definition above leans on 5 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what branch circuit, multiwire covers:
- Grounded Conductor — IRC 2009: A system or circuit conductor that is intentionally grounded.
- Branch Circuit — IRC 2009: The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).
- Ungrounded — IRC 2009: Not connected to ground or to a conductive body that extends the ground connection.
- Conductor — IPC 2009: A pipe inside the building that conveys storm water from the roof to a storm or combined bUilding drain.
- Branch — IRC 2009: Any part of the piping system other than a riser, main or stack.
Branch Circuit, Multiwire: what to open, and in what order
Every row is a document this term depends on. The ICC code library and the ICC adoption maps cover the middle rows.
| Check | Where | Confirmed |
|---|---|---|
| Read the definition in the adopted IRC | Electrical Definitions | |
| Re-check the requirement that uses it | Branch Circuit and Feeder Requirements (IRC 2009) | |
| Re-check the requirement that uses it | Services (IRC 2009) | |
| Re-check the requirement that uses it | General Requirements (IRC 2009) | |
| Re-check the requirement that uses it | Electrical Definitions (IRC 2009) | |
| Confirm the dependent definition | Grounded Conductor | |
| Confirm the dependent definition | Branch Circuit | |
| Confirm the dependent definition | Ungrounded | |
| Local amendment to any of the above | Jurisdiction's amendment list |
A research aid, not a code determination. The authority having jurisdiction decides which edition and which amendments apply.
Where can you explore related guidance?
- Explore all glossary guidance
- Grounded Conductor: Building Code Definition
- Branch Circuit: Building Code Definition
- Ungrounded: Building Code Definition
- Conductor: Building Code Definition
Sources and method
Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The ICC code library publishes the current model text and the ICC adoption maps show which edition a jurisdiction has adopted; those sources control.
Source links
Frequently asked questions
What is the code definition of branch circuit, multiwire?
The International Residential Code (IRC) 2009 defines it in Electrical Definitions as: “A branch circuit consisting of two or more ungrounded conductors having voltage difference between them, and a grounded conductor having equal voltage difference between it and each ungrounded conductor of the circuit, and that is connected to the neutral or grounded conductor of the system.” The 2009 model text is reproduced here; the definition that binds your project is the one in the edition your jurisdiction has adopted, as amended locally.
Which parts of the code depend on branch circuit, multiwire?
In this corpus the term is used across 4 chapters, led by Branch Circuit and Feeder Requirements in the IRC 2009. Those are the sections whose scope moves if the definition is amended locally, so read them together with Chapter 2 rather than on their own.
What is considered a multiwire branch circuit?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Electrical Definitions: “A branch circuit consisting of two or more ungrounded conductors having voltage difference between them, and a grounded conductor having equal voltage difference between it and each ungrounded conductor of the circuit, and that is connected to the neutral or grounded conductor of the system.” It is defined in IRC 2009. Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.
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