FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Fine Homebuilding Project Guides

Wiring

Guide Home
  • Working with Electricity
  • Tools and Materials
  • Receptacles and Switches
  • Lights and Fans
  • Rough-In
  • Outdoor Wiring
  • Panels and Subpanels
How it Works

Electrical Breaker Panels

The job of the breaker panel is to distribute the incoming power to the separate circuits throughout a home’s electrical system.

By Clifford A. Popejoy Issue 257 - Feb/Mar 2016
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

Synopsis: The job of an electrical breaker panel is to distribute power to the different circuits in a house’s electrical system, and to do so in a way that reduces the risk of an electrical fire. Here, electrician Cliff Popejoy identifies the different parts of an electrical breaker panel and explains how they work.


The National Electrical Code (NEC) calls breaker panels, panel boards, a name given to the earliest whole-house electrical systems—including those with switches and screw-in, Edison-type fuses— which were mounted on wooden or asbestos panels.

By the mid-1960s, breakers had almost completely replaced Edison-type fuses in new construction, so the old panel-mounted fuse boxes gave way to the metal breaker panels that are still being used today.

Although the panel shown here is based on modern NEC requirements, older service/ main panel configurations may differ. That doesn’t mean your old electrical panel necessarily requires an upgrade. If an old panel meets code requirements appropriate for when it was installed, the workmanship was good, and the panel has been maintained, then an upgrade is not required.

The job of the breaker panel is to distribute the incoming power to the separate circuits throughout a home’s electrical system, and to reduce the risk of a fire if something goes wrong with the wiring. Here’s how it works.

Panel basics

Beneath the metal cover and beyond the wires and breakers, the design of your home’s main breaker panel is simple. Although configurations vary based on panel size, type, and brand, the basic components are similar.

  1. Main lugs– These threaded connectors are the main point of connection between incoming electricity and the panel that distributes the power to the house. If the utility is connected, these lugs are live.
  2. Main circuit breaker– This is the master switch for the breaker panel. It shuts off the power to everything downstream, including the hot bus bars and all breakers mounted to them.
  3. Hot bus bars– These metal bars, typically made of aluminium or copper, are mounted to the panel on plastic insulators and have tabs that connect with and channel electricity to the clips on the back of the branch circuit breakers. Each of the two conductors feeds one side of the hot bus-bar section.
  4. Neutral bus bars– The role of the neutral bus bars, which are typically strips of aluminium bored with holes to secure and connect wires, is to act as a hub for the neutral wires returning from each circuit in the panel, completing the loop of electricity. Some panels may have just one neutral bus bar.
  5. Ground bars– These metal bars are the central safety hub for the panel and the ground wires for circuits connected to the panel. They create a direct path for errant power to be discharged safely to the earth.

The flow of power

With breakers installed and wires connected, the panel is ready to receive power from the utility and distribute it through the house. Here’s how the components combine to make a complete system.

  1. Breakers control the flow. Besides acting as manual shutoff switches, branch circuit breakers are designed to cut power automatically under hazardous conditions. Thermal-magnetic breakers are the most common type. They trip, cutting off power, in two different ways. When a circuit is carrying more current than it is designed to handle, a bimetal strip inside the breaker heats up, bends, and releases a spring-loaded mechanism to physically break the electrical connection. If there is an inadvertent connection between the hot and the neutral (referred to as a short circuit) or between the hot—or anything energized—and anything that’s grounded (referred to as a ground fault), an internal electromagnet will pull the electrical contacts apart.
    GFCI breakers are required in areas where there is a greater possibility of shock or electrocution if there’s a fault. They measure the power going out on the hot and the power returning on the neutral, and disconnect if they detect a difference, preventing severe shock or electrocution. AFCI breakers, now required in most rooms of the house, use a circuit board to monitor and protect against problems stemming from arcing wires (chewed, frayed, or poorly connected wires that spark). While usually not enough to trip a regular breaker, these sparks can be enough to start a fire.
  2. Neutrals complete the circuit. After the electricity has dropped off its energy at the load (lamp, TV, heater, etc.), it returns to the panel via the white-insulated neutral wire. The individual branch-circuit neutrals are connected to a neutral bar, which ties directly to the much larger neutral-service conductor, returning the electricity to the utility to complete the loop.
  3. Grounding is for safety. For tools, light fixtures, table lamps, appliances, and any other electrical devices that have exposed metal parts, there is the possibility that a frayed or damaged wire inside might touch an exposed metal part, creating a risk of shock or electrocution for someone who touches the metal. A ground conductor connected to the metal case of the device runs back to the panel, where it connects to an equipment grounding terminal bar (usually referred to as a ground bar). This allows the electricity to flow back to the panel, creating a short circuit that will trip the breaker and kill the power to that circuit. The ground bar is connected to the earth via ground electrodes, which also protect the system as a whole in the event of a lightning strike or other high-energy, high-voltage pulse traveling through the service conductors.

Photos by Rodney Diaz; drawing by Christopher Mills


RELATED LINKS

  • Installing an Electrical Service
  • Organizing a Panel Box

From Fine Homebuilding #257

View PDF
Next: Understanding Service Panels

Guide

Wiring

Chapter

Panels and Subpanels

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Wiring

Wiring

Trusted, code-compliant guidance from the pros for working safely on any wiring project

View Project Guide

View All Project Guides »

Become a member and get unlimited site access, including the Wiring Project Guide.

Start Free Trial

Working with Electricity
  • Basics
  • Safety
  • Troubleshooting and Upgrades
Tools and Materials
  • Electrical Tools
  • Electrical Boxes
  • Cables and Wires
Receptacles and Switches
  • Materials
  • Wiring Receptacles
  • Wiring Switches
Lights and Fans
  • Lighting Design
  • Installing Lights
  • Fans
Rough-In
  • Planning
  • Installing Electrical Boxes
  • Running Cable
  • Retrofit Work
  • Making Connections in Boxes
  • Electrical Conduit
Outdoor Wiring
  • Basics
  • Outlets
  • Installing Lighting
Panels and Subpanels
  • Understanding Panels
  • Circuits
  • Installing a Subpanel

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Project Guides
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 81%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data