How to Choose the Right Circuit Breaker
Learn how to select the perfect breaker for your project based on load requirements, application, and safety standards.

Electrical Supplies Unlimited (ESU) is your trusted source for Circuit Breakers in Miramar San Diego, serving contractors, electricians, property managers, and homeowners throughout Miramar and surrounding communities including University City, Hillcrest, Golden Hill, Bankers Hill, and greater San Diego County.
We buy and sell both new and used circuit breakers, electrical panels, transformers, and electrical equipment. Whether you need replacement breakers, obsolete breakers, or hard-to-find electrical components, ESU provides dependable solutions backed by over 40 years of industry experience.
ESU has proudly served the San Diego electrical supply industry for more than four decades. As a fully stocked electrical distributor and wholesaler, we carry a wide range of residential, commercial, and industrial electrical supplies designed to meet virtually any project requirement.
Our experienced team specializes in locating discontinued, surplus, and specialty electrical products, helping customers source reliable solutions quickly and efficiently.
Our extensive inventory includes major circuit breaker manufacturers and trusted industry brands, including:
General Electric (GE), Siemens / ITE, Cutler Hammer, Square D, Federal Pacific (FPE), Pushmatic, Zinsco, Challenger, Bryant, Westinghouse, Sylvania, Crouse Hinds, Bulldog, and many more.
In addition to circuit breakers, ESU stocks a large inventory of:
We also offer Greenlee tool rentals, conduit benders, wire pullers, and additional electrician equipment for contractors throughout San Diego County.
ESU is San Diego’s go-to source for new, used, surplus, and obsolete circuit breakers. We carry a broad range of amperages and voltages for nearly every major electrical system.
Examples of our inventory include:
Whether you need residential breaker replacements, commercial electrical upgrades, or industrial breaker solutions, our knowledgeable staff can help you select the right product for your project.
We proudly provide circuit breakers and electrical supplies throughout:
We also ship many products nationwide for customers outside the San Diego region.
At Electrical Supplies Unlimited, we combine decades of electrical supply expertise with one of the region’s most diverse inventories of circuit breakers and electrical equipment.
Whether you’re replacing outdated breakers, sourcing specialty equipment, or upgrading electrical infrastructure, ESU delivers dependable products, expert guidance, and exceptional customer service.
Call ESU today at 858.558.2850 to speak directly with one of our electrical supply specialists and find the right circuit breaker or electrical solution for your needs.
Circuit Breakers Bay Ho San DiegoElectrical Supplies Unlimited (ESU) is your trusted source for Circuit Breakers in Bay Ho San Diego, serving contractors, electricians, property managers, and homeowners throughout Bay Ho and surrounding communities including University City, Hillcrest, Golden Hill, Bankers Hill, and greater San Diego County.
We buy and sell both new and used circuit breakers, electrical panels, transformers, and electrical equipment. Whether you need replacement breakers, obsolete breakers, or hard-to-find electrical components, ESU provides dependable solutions backed by over 40 years of industry experience.
ESU has proudly served the San Diego electrical supply industry for more than four decades. As a fully stocked electrical distributor and wholesaler, we carry a wide range of residential, commercial, and industrial electrical supplies designed to meet virtually any project requirement.
Our experienced team specializes in locating discontinued, surplus, and specialty electrical products, helping customers source reliable solutions quickly and efficiently.
Our extensive inventory includes major circuit breaker manufacturers and trusted industry brands, including:
General Electric (GE), Siemens / ITE, Cutler Hammer, Square D, Federal Pacific (FPE), Pushmatic, Zinsco, Challenger, Bryant, Westinghouse, Sylvania, Crouse Hinds, Bulldog, and many more.
In addition to circuit breakers, ESU stocks a large inventory of:
We also offer Greenlee tool rentals, conduit benders, wire pullers, and additional electrician equipment for contractors throughout San Diego County.
ESU is San Diego’s go-to source for new, used, surplus, and obsolete circuit breakers. We carry a broad range of amperages and voltages for nearly every major electrical system.
Examples of our inventory include:
Whether you need residential breaker replacements, commercial electrical upgrades, or industrial breaker solutions, our knowledgeable staff can help you select the right product for your project.
We proudly provide circuit breakers and electrical supplies throughout:
We also ship many products nationwide for customers outside the San Diego region.
At Electrical Supplies Unlimited, we combine decades of electrical supply expertise with one of the region’s most diverse inventories of circuit breakers and electrical equipment.
Whether you’re replacing outdated breakers, sourcing specialty equipment, or upgrading electrical infrastructure, ESU delivers dependable products, expert guidance, and exceptional customer service.
Call ESU today at 858.558.2850 to speak directly with one of our electrical supply specialists and find the right circuit breaker or electrical solution for your needs.
Thermal magnetic circuit breakers are one of the most widely used types of circuit protection in residential, commercial, and industrial electrical systems. They combine two separate protection mechanisms—thermal protection for overloads and magnetic protection for short circuits—making them highly reliable and efficient.
These breakers are commonly found in modern electrical panels and are essential for protecting wiring, appliances, and electrical systems from damage caused by excessive current.
Thermal magnetic circuit breakers use a dual protection system:
This combination allows the breaker to protect against both slow-building overloads and sudden electrical faults.
These breakers are standard in many electrical applications, including:
In San Diego, they are commonly used in both new construction and panel upgrades to meet modern electrical code requirements.
Unlike specialty breakers such as AFCI or GFCI breakers, thermal magnetic breakers focus on core electrical protection. They do not provide arc-fault or ground-fault protection but are essential as the primary layer of circuit safety.
Learn more about other breaker types in our guide on circuit breaker types and applications.
You may need to replace a breaker if you notice:
If your breaker is frequently tripping, visit our guide on why circuit breakers keep tripping.
Thermal magnetic circuit breakers are commonly used throughout San Diego homes and businesses due to their reliability and compliance with electrical code standards.
They are often installed during:
For local electrical solutions, visit our main page on circuit breakers in San Diego.

Welcome to ESU’s Circuit Breaker Resources Hub — your ultimate guide to understanding, selecting, and maintaining circuit breakers for residential, commercial, and industrial applications. Whether you’re an electrician, contractor, or a homeowner looking to upgrade your electrical panel, this hub provides authoritative guides, brand comparisons, safety tips, and troubleshooting advice to help you make informed decisions.
Circuit breakers are the heart of any electrical system. They protect your home, business, or industrial facility from electrical overloads and short circuits, preventing fires and costly equipment damage. Selecting the right circuit breaker is essential for safety, compliance, and long-term reliability.
Our resources cover all aspects of circuit breakers, from low voltage residential breakers to medium voltage industrial solutions, and help you navigate the many brands, types, and technical specifications available.
Below, you’ll find our full library of guides — each page is designed to provide in-depth knowledge, actionable tips, and expert advice:
Learn how to select the perfect breaker for your project based on load requirements, application, and safety standards.
Discover how low voltage breakers work in residential and light commercial applications, including installation tips and common brands.
Explore medium voltage breakers used in industrial and commercial settings, including compliance and safety guidelines.
Compare popular brands like Square D, Eaton, Cutler Hammer, and Challenger to find the best option for your system.
Step-by-step solutions for common breaker problems, including tripping, failure, and maintenance tips.
Essential safety tips to protect your home and family from electrical hazards.
Expert guidance on safely replacing outdated or unsafe breakers in older panels.
Insights for industrial and commercial installations, including brand recommendations and maintenance best practices.
Everything you need to know to buy the right circuit breaker for your project, from residential panels to industrial systems.
We are circuit breakers and electrical hardware experts. Do not hesitate to call us at 858.558.2850 to find out which Circuit Breaker is right for your requirement.
Your one stop go to guys. Always at your service!
Many homes, commercial buildings, and industrial facilities continue to operate with electrical panels that require discontinued circuit breakers. When a breaker fails or additional circuits are needed, locating a compatible replacement can be challenging. Electrical Supplies Unlimited (ESU) specializes in helping customers find replacement breakers for obsolete and discontinued electrical systems throughout San Diego and Southern California.
Whether you're an electrician, contractor, facility manager, or property owner, understanding your options for discontinued breakers can help extend the life of your electrical system and avoid unnecessary panel replacement costs.
What Are Discontinued Circuit Breakers?Discontinued circuit breakers are breakers that are no longer manufactured by the original company. Although production has ended, many of these breakers remain in service in residential, commercial, and industrial electrical panels throughout the United States.
As electrical equipment ages, replacement breakers often become difficult to locate through traditional electrical supply channels. This creates a growing demand for surplus, obsolete, and hard-to-find replacement breakers.
Some of the most frequently requested discontinued breaker brands include:
Many of these systems were installed decades ago and continue operating today, making replacement breakers an ongoing necessity.
Manufacturers discontinue breaker lines for several reasons:
Even when production ends, many panels remain functional and continue requiring replacement components for maintenance and repairs.
In many cases, yes. Discontinued breakers are often available through specialized suppliers that deal in surplus, obsolete, and hard-to-find electrical equipment.
Replacement options may include:
Working with an experienced electrical supplier can help ensure compatibility and safe operation.
Among the most searched discontinued breaker brands are Federal Pacific (FPE), Zinsco, and Challenger. These panels remain common in older residential and commercial buildings throughout California.
Learn more in our guide on Replacing FPE, Zinsco, and Challenger Breakers.
Before purchasing a replacement breaker, it's important to identify:
If labels are missing or difficult to read, an experienced electrical supplier may be able to identify the breaker based on physical appearance and panel information.
Visit our Circuit Breaker Identification Guide for additional help.
Although replacement breakers are often available, some electrical systems may benefit from a complete panel upgrade.
Factors that may indicate a panel replacement is appropriate include:
Learn more in our guide on When to Upgrade Your Electrical Panel.
Electrical Supplies Unlimited maintains inventory of many discontinued, obsolete, and hard-to-find circuit breakers for customers throughout San Diego County. Our team works with electricians, contractors, maintenance departments, and property managers to help locate replacement breakers quickly and efficiently.
Whether you need a discontinued residential breaker, a commercial panel component, or a hard-to-find industrial breaker, ESU can help identify and source the right solution.
For more than 40 years, Electrical Supplies Unlimited has been one of San Diego's trusted sources for circuit breakers, transformers, electrical panels, and obsolete electrical equipment.
We specialize in helping customers find replacement breakers that many traditional suppliers can no longer obtain.