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Today’s topic is on residential grade 120v/240v rated circuit breakers also known as overload protective devices. We will go over what a circuit breaker is, what is the circuit breaker role in an electrical installation and finally how are circuit breakers classified from a Phoenix electrician point of view.

What is a circuit breaker from a Phoenix electrician point of view?

A circuit breaker is an overload protective device that automatically interrupts the flow of current in a live circuit. The purpose of a circuit breakers is to interrupt the flow of electricity to any given circuit in the attempt to preserve the integrity of the electrical wiring. When current flows through an electrical wire heat is generated as a byproduct. The job of the breaker is to interrupt the power when the operating temperature & amperage of the circuit is close to exceeding the maximum operating temperature & amperage rating of the electrical wiring. In basic terms the circuit breaker exists to prevent the wiring from being overloaded which could lead to an electrical fire.

How do circuit breakers work?

Standard circuit breakers are primarily composed of these two components: spring loaded switch and bimetallic strip. The bimetallic strip acts as trigger for the spring loaded switch. When the bimetallic strip reaches a certain temperature and begins to warp it trips the spring loaded system acting as an automated shut off system in a circuit that is either being overloaded or a short circuit is present.

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Residential grade 120V & 240V rated circuit breakers are classified by the following:

Operating voltage

The operating voltage of a circuit breaker refers to the maximum voltage the breaker was designed to safely handle. In a residential scenario the two common voltages would be 120v and 240v. Most plug and play appliances are 120v rated in a home such as floor lamps, hair blow dryers and blenders. An example of 240v rated appliances in a residence would be a full size 50 amp electrical range, 30 amp electric water heater and an electric furnace.

Amperage rating

All circuit breakers have different maximum amperage ratings. An amperage rating is the amount of current you can put through the circuit breaker before it trips. This important detail is generally found on the lever or the top spine of the circuit breaker. The most common amperage ratings utilized in residential electrical system applications are 15A, 20A, 25A, 30A, 35A, 40A, 50A, 60A, 70A, 80A, 90A, 100A, 125A, 175A, 200A, 225A, 275A, 300A, 400A ETC.

Tandem breakers

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This type of circuit breaker is what I call two single pole breakers in one. It is the size of one standard single pole breaker but has two levers and  two outputs instead of one. This type of breaker only takes up one slot at the main panel but generates two completely isolated outputs. What I mean by isolated outputs is that both outputs function independently from each other. If one lever/output trips the other will continue to operate.

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Amount of poles


In single phase residential systems 1 pole or 2 pole breakers are utilized. Single pole breakers physically take only one slot at the panel and 2 pole circuit breakers take up two vertical slots. The reason for having 1 pole & 2 pole breakers is because in a residential scenario the single pole breakers will deliver 120v and a double pole breakers will deliver 240v to the circuit it supplies. An easy way to put this would be that the single pole breakers in a home supply power to outlets and light fixtures and the two pole circuit breakers supply power to the bigger appliances in the home such as water heaters, air condition units and electric ranges.

Quad circuit breakers

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This type of circuit breaker is similar to the Tandem breaker we discussed. It is basically combining two tandem breakers together. This type of circuit breaker gives you a total of 4 outputs and 4 poles. The most important features of this quad circuit breaker is that it allows you to create two 240v circuits by only using two slots at the load center panel. Now there is a catch when utilizing quad circuit breakers and that is that they may only be utilized on approved load centers.

Circuit breaker brands

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Circuit breaker brands are very important and it is not recommended to mix and match them unless approved by the load center manufacture you are specifically working on. An example of miss and match would be if you have a Siemens main panel it would be a fire hazard to install square D circuit breakers. Now there are cases where one breaker brand is allowed to be installed in different manufacture brand panels. One of the exceptions is the EATON brand which is compatible with Cutler Hammer, Westinghouse and Bryant. Furthermore some of the most well-known brands are: Cutler Hammer, Siemens, Square D HOM, General Electric, Square D QO, Cutler Hammer CH & EATON.

In conclusion  we can all agree that circuit breakers are a must have in any sort of electrical installation whether you are a homeowner or a Phoenix electrician. Having overload protective devices gives us peace of mind and provides a fail-safe for when things actually go wrong whether its due to lack of maintenance or user malpractice.  

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Until next time, friends.

Hector and Kathryn Torres (the power couple)