# Circuit Breaker: Building Code Definition > How the IRC 2009 define circuit breaker, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/circuit-breaker/ - Last updated: 2026-09-07 - Data source: 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. ## Key facts | Fact | Value | | --- | --- | | Defined in | IRC 2009 (2009 editions transcribed in this corpus) | | Primary source | IRC 2009 Electrical Definitions (model text, not a jurisdiction's adopted text) | | Chapters using the term | 8 (counted across the codes hosted here) | | Wording identical across codes | Single code (compare before citing one code's wording under another) | ## Direct answer Circuit breaker is a defined term in the International Residential Code (IRC) 2009, in Electrical Definitions. The code's own words are: “A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating.” 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 8 chapters of this corpus, most often in Services (IRC 2009), Devices and Luminaires (IRC 2009), Branch Circuit and Feeder 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](https://nz.linkedin.com/in/barrington), Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.* ## What does this term mean? **Circuit Breaker** — IRC 2009, Electrical Definitions: > A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating. ![Labeled code-term definition diagram: Circuit Breaker: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/circuit-breaker/diagram-1344.webp) *How the IRC 2009 define circuit breaker, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? **Circuit Breaker** is defined once in this corpus, in the [Electrical Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/electrical-definitions.md) chapter of the International Residential Code (IRC) 2009: > A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating. ## Where circuit breaker is used in the code The term appears in 8 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [Services](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/services.md) | IRC 2009 | 11 | | [Devices and Luminaires](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/devices-and-luminaires.md) | IRC 2009 | 10 | | [Branch Circuit and Feeder Requirements](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/branch-circuit-and-feeder-requirements.md) | IRC 2009 | 6 | | [Electrical Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/electrical-definitions.md) | IRC 2009 | 3 | | [Commercial Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/commercial-energy-efficiency.md) | IECC 2009 | 1 | | [Welding and Other Hot Work](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/welding-and-other-hot-work.md) | IFC 2009 | 1 | | [Appliance Installation](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/appliance-installation.md) | IRC 2009 | 1 | | [Power and Lighting Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/power-and-lighting-distribution.md) | IRC 2009 | 1 | ### The term in use How the code actually writes about circuit breaker, quoted from the 2009 text hosted here: > Overcurrent devices shall not be connected in series with a grounded service conductor except where a circuit breaker is used that simultaneously opens all conductors of the circuit. — [IRC 2009 §E3603.3.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/services.md) > Where single-throw switches or circuit breaker handles are operated vertically rather than rotationally or horizontally, the up position of the handle shall be the ON position. — [IRC 2009 §E4001.3](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/devices-and-luminaires.md) > A switch or circuit breaker shall be provided so that fixed electric welders and control equipment can be disconnected from the supply circuit. — [IFC 2009 §2606.4](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/welding-and-other-hot-work.md) ## The terms circuit breaker is built out of The definition above leans on 2 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what circuit breaker covers: - **[Overcurrent](https://harth.build/resources/glossary/overcurrent.md)** — IRC 2009: Any current in excess of the rated current of equipment or the ampacity of a conductor. - **[Device](https://harth.build/resources/glossary/device.md)** — IRC 2009: Aunit of an electrical system that carries or controls electrical energy as it principal function. ## Circuit Breaker: what to open, and in what order Every row is a document this term depends on. The [ICC code library](https://codes.iccsafe.org/codes) and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-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 | Services (IRC 2009) | | | Re-check the requirement that uses it | Devices and Luminaires (IRC 2009) | | | Re-check the requirement that uses it | Branch Circuit and Feeder Requirements (IRC 2009) | | | Re-check the requirement that uses it | Electrical Definitions (IRC 2009) | | | Confirm the dependent definition | Overcurrent | | | Confirm the dependent definition | Device | | | 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](https://harth.build/resources/glossary.md) - [Overcurrent: Building Code Definition](https://harth.build/resources/glossary/overcurrent.md) - [Device: Building Code Definition](https://harth.build/resources/glossary/device.md) ## 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](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. ### Source links - [codes.iccsafe.org](https://codes.iccsafe.org/codes) - [iccsafe.org](https://www.iccsafe.org/advocacy/code-adoption-maps/) ## Frequently asked questions ### What is the code definition of circuit breaker? The International Residential Code (IRC) 2009 defines it in Electrical Definitions as: “A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating.” 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 circuit breaker? In this corpus the term is used across 8 chapters, led by Services 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 the definition of circuit breaker? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Electrical Definitions: “A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating.” 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. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fcircuit-breaker%2F - View this page in a browser: https://harth.build/resources/glossary/circuit-breaker/ - All resources for agents: https://harth.build/llms.txt