# Panelboard: Building Code Definition

> How the IRC 2009 define panelboard, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/panelboard/
- 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 | 7 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Panelboard is a defined term in the International Residential Code (IRC) 2009, in Electrical Definitions. The code's own words are: “A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat or power circuits, designed to be placed in a cabinet or cutout box placed in or against a wall …” 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 7 chapters of this corpus, most often in Branch Circuit and Feeder Requirements (IRC 2009), Swimming Pools (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](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?

**Panelboard** — IRC 2009, Electrical Definitions:

> A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat or power circuits, designed to be placed in a cabinet or cutout box placed in or against a wall, partition or other support and accessible only from the front.

![Labeled code-term definition diagram: Panelboard: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/panelboard/diagram-1344.webp)

*How the IRC 2009 define panelboard, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

**Panelboard** 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 single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat or power circuits, designed to be placed in a cabinet or cutout box placed in or against a wall, partition or other support and accessible only from the front.

## Where panelboard is used in the code

The term appears in 7 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](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/branch-circuit-and-feeder-requirements.md) | IRC 2009 | 15 |
| [Swimming Pools](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/swimming-pools.md) | IRC 2009 | 15 |
| [General Requirements](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/general-requirements.md) | IRC 2009 | 11 |
| [Power and Lighting Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/power-and-lighting-distribution.md) | IRC 2009 | 10 |
| [Building Services and Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/building-services-and-systems.md) | IFC 2009 | 5 |
| [Electrical Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/electrical-definitions.md) | IRC 2009 | 1 |
| [Services](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/services.md) | IRC 2009 | 1 |

### The term in use

How the code actually writes about panelboard, quoted from the 2009 text hosted here:

> All conductors for multiwire branch circuits shall originate from the same panelboard or similar distribution equipment.

— [IRC 2009 §E3701.5](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/branch-circuit-and-feeder-requirements.md)

> The junction box, transformer enclosure, or other enclosure in the supply circuit to a wet-niche or no-niche luminaire and the field-wiring chamber of a dry-niche luminaire shall be grounded to the equipment grounding terminal of the panelboard.

— [IRC 2009 §E3908.12](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/swimming-pools.md)

> The space equal to the width and depth of the panelboard and extending from the floor to a height of 6 feet (1829 mm) above the panelboard, or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation.

— [IRC 2009 §E3405.3](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/general-requirements.md)


## The terms panelboard 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 panelboard 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.
- **[Accessible](https://harth.build/resources/glossary/accessible.md)** — IBC 2009: A site, building, facilityor portion thereof that complies with this chapter.
- **[Cutout Box](https://harth.build/resources/glossary/cutout-box.md)** — IRC 2009: An enclosure designed for surface mounting and having swinging doors or covers secured directly to and telescoping with the walls of the box proper (see "Cabinet").
- **[Automatic](https://harth.build/resources/glossary/automatic.md)** — IBC 2009: As applied to fire protection devices, a device or system providing an emergency function without the necessity for human intervention and activated as a result of a predetermined temperature rise, rate of temperature rise or combustion products.
- **[Control](https://harth.build/resources/glossary/control.md)** — IRC 2009: A manual or automatic device designed to regulate the gas, air, water or electrical supply to, or operation of, a mechanical system.

## Panelboard: 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 | Branch Circuit and Feeder Requirements (IRC 2009) | |
| Re-check the requirement that uses it | Swimming Pools (IRC 2009) | |
| Re-check the requirement that uses it | General Requirements (IRC 2009) | |
| Re-check the requirement that uses it | Power and Lighting Distribution (IRC 2009) | |
| Confirm the dependent definition | Overcurrent | |
| Confirm the dependent definition | Accessible | |
| Confirm the dependent definition | Cutout Box | |
| 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)
- [Cutout Box: Building Code Definition](https://harth.build/resources/glossary/cutout-box.md)
- [Accessible: Building Code Definition](https://harth.build/resources/glossary/accessible.md)
- [Automatic: Building Code Definition](https://harth.build/resources/glossary/automatic.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 panelboard?

The International Residential Code (IRC) 2009 defines it in Electrical Definitions as: “A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat or power circuits, designed to be placed in a cabinet or cutout box placed in or against a wall, partition or other support and accessible only from the front.” 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 panelboard?

In this corpus the term is used across 7 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 the definition of a panelboard?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Electrical Definitions: “A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat or power circuits, designed to be placed in a cabinet or cutout box placed in or against a wall …” 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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