Understanding Your Home’s Main Circuit Breaker

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Posted March 28, 2019

Performing electrical repairs in your home require you to understand how to use the main circuit breaker. Your homes main circuit breaker controls the distribution of electricity to each room. The circuit breaker manages the connection between your home and your utility company.

The utility company pumps electricity to your home through a service drop electrical line. The power from your service drop never shuts off, but your circuit breaker can stop the power from flowing through to your house. So, everything you need to perform electrical work or restore power after an overload is in the breaker box.

This article provides a complete guide to understanding your homes main circuit breaker. A step-by-step reference guide that teaches you about everything you see when you look at the breaker box. And, learn the difference between the main breaker and the branch breaker.

This guide is for educational purposes only. Before performing any electrical repairs on your own, you should always consult a professional electrician near you.

The Complete Main Circuit Breaker Guide for Beginners

Your main circuit breaker is on your electrical service panel box. If you are wondering where it is located in your house, look for the electrical service panel box in your basement or garage. Sometimes they are near your water heater or near the laundry.

In apartments and some older buildings, the service panel is built into the wall. It looks like a metal cabinet door and is tough to pull open at first. When you open the panel door, you see a row or two of circuit breaker switches.

The switches might be numbered, and if your home has a previous owner, they might even be labeled. These are your branch circuit breakers. Each breaker branches off to an area, like the upstairs hallway, living room, or basement.

Look above the branch circuit breaker and you see another switch that is larger than the branch switches. This is your main circuit breaker which controls the flow of power to your branch breaker.

The main circuit breaker switch usually faces perpendicular to your branch circuit breaker switches. It sometimes looks like three or four breakers, together, with a single on/off breaker switch. Pull the main circuit breaker switch off and there is no power going to the circuit breaker panel.

What is a Circuit Breaker?

Circuit breakers are a protective measure against damage to a circuit in the event of an electrical current overload. In other words, it makes sure that nothing breaks if you have too many appliances on at the same time and cause a short circuit.

The circuit breaker, itself, is an electrical switch. It connects to your circuit board and interrupts the flow of electrical current if it detects a fault in the flow. In the event of a fault, the breaker switch automatically pops off and stops the electricity from flowing through the circuit.

Circuit breakers are built to safety specifications to ensure that a short circuit does not cause damage to the home or building. Before circuit breakers, in the event of a power surge, you had to replace a blown fuse.

Fuses also protected against electrical fires, but only once and then you had to replace the blown fuse. With a circuit breaker, all you do is unplug some of the appliances that caused the power surge, and flip the circuit breaker switch back to the “on” position.

Circuit breakers work so well that they come in a wide range of sizes and types. Almost all residential circuit breakers are low voltage. An apartment building uses a medium-voltage circuit breaker, and a high-voltage circuit breaker is for utility companies that feed power to an entire city.

How Does a Circuit Breaker Work?

Different types of circuit breakers operation vary, but every circuit breaker performs a uniform function. Other factors that affect the breakers means of operation include the voltage class and current rating specifications.

At its core, a circuit breaker detects faults in the current flow of a circuit and interrupts the circuits’ power delivery. When an electric current passes through two contacts it takes considerable force to separate the connection. For this reason, a circuit must be broken by force in order to stop the transfer of electricity.

The low-voltage circuit breakers on your homes electrical panel are the simplest kinds of circuit breakers. They use the stored energy in the spring to throw the switch and separate contact with the circuit. This enables you to manually cut-off and resets the power delivery with the flip of a switch.

Inside the circuit breaker contacts to carry the electricity. They must deliver the load without overheating from a power surge or arc. Too much current or heat triggers fault parameters and trips the breaker.

An arc happens when the current delivery is interrupted when the breaker trips. An arc is extremely hot and erodes the contact material in the circuit. When the contacts experience a fault the connection must be broken–hence the name.

The circuit contacts are made out of highly conductive metals, like copper and silver alloy. The higher the voltage, the longer the arc created when the connection is interrupted. The stronger the current, the hotter the arc is when the breaker trips.

So, the breakers and circuits are matched, as to not exceed the acceptable current and voltage fault parameters. In the event of an overload to the circuit, the breaker switch triggers with enough force to break the current connection and the subsequent arc.

The breaker switch severs the electrical connection if the contacts preserve an excess of heat or current flow. As soon as the fault is perceived, the breaker trips. To restore current flow the interrupted contact must be closed by resetting the breaker switch.

All circuit breakers function for the purpose of interrupting the connection between the circuit contacts. However, there is a difference between the branch circuit breaker and the main circuit breaker.

Branch Breaker vs Main Breaker

The branch breakers and the main breaker are, basically the same thing, but not quite. They function in the same way, but the branch breakers are smaller. The main breaker is designed to interrupt a larger amperage load.

The two power lines that bring electricity into your home run through the service panel. Each of the main wires carries 120 volts of electricity, equaling 240 volts in total. The main breaker attaches directly to these two wires.

Below the main breaker, the two wires connect to two electrically conductive bars, called hot buss bars. The hot bus bars are where you attach individual branch circuit breakers, which is why they often appear as two parallel rows.

The main circuit breaker controls the electricity flow from your two main wires to your hot buss bars. Tripping the main circuit breaker disrupts the 240 volts of electricity before it reaches your branch breakers. When the main breaker is tripped, everything in your home is off.

How to Perform a Main Circuit Breaker System Shutoff

If you need to do major electrical work on your system, use your main breaker as a system shutoff. Do not just shut off the main circuit breaker right away. First, start at the top of your branch breaker and shut off each breaker, individually.

When you are sure that you successfully turned off each branch breaker, one at a time, perform a system shutoff by flipping your main circuit breaker switch to the “off” position. Power should be out for your entire property.

After you complete your work and are ready to turn the power back on, reverse the process. Turn the main circuit breaker to the “on” position, before turning on your branch breakers. Then, take your time as you flip each branch breaker back on, one-by-one.

You do not want to create a power surge by placing too high demands on your electrical system all at one time. So take a few seconds in between each branch breaker.

As always, we highly recommend contacting a licensed, electrician before performing your own electrical work.

How to Reset a Tripped Main Circuit Breaker

The main circuit breaker can trip for several reasons. If the power company causes a surge it can trip the main breaker for every house on the street. A faulty branch breaker can cause the main breaker to trip as a secondary precaution.

If the main circuit breaker gets tripped you must reset it correctly to avoid a surge to your system. When power is restored, any branch breaker that is “on” will engage the circuits driving motor. If all of the motors engage at once it places stress on your system and increases the likelihood of a short-circuit.

Before trying to reset your main breaker, get safety goggles and hardware gloves. Sometimes some sparks can fly when you flip the main breaker back on. And, stand off to the side whenever flipping breakers to avoid sparks in your face.

When your main breaker trips, start by turning each individual branch breaker to the “off” position. When all the breakers are off, turn your main breaker back on. The power should remain off since your branch breakers are disengaged.

Now, slowly turn the branch breakers on, one at a time to avoid an overload. Each time you flip a branch breaker back to the “on” position, power should return to the areas in your home controlled by that circuit.

The main circuit breaker should not trip easily and each time it trips the connections weaken. If you experience frequent main circuit breaker trips call a professional electrician for help. It could be indicative of a serious electrical system issue or faulty wiring throughout your home.

Why do You Need a Main Circuit Breaker?

The main circuit breaker provides a safety measure that is reliable. Without the main circuit breaker, you are relying on each of your branch breakers to handle a much larger load than they are designed for. And, shutting off the power to the whole house comes in handy when you are doing any electrical work.

In the event that any individual branch circuit is drawing too much power, it should simply trip the branch breaker. But, if too many of your branch breakers are drawing too much power the main circuit breaker protects you from a dangerous overload.

It is essential to kill power to your electric box whenever you perform electrical work at home. Cutting into a live wire is a mistake you won’t make twice, because you won’t get the chance. Whether you are installing track lighting or putting in extra wall outlets, the main circuit breaker protects you from electrocution.

None of your circuit breakers should be tripping on a regular basis. If you find yourself resetting the breaker regularly it might be time to upgrade your electrical panel.

Final Thoughts

Your homes electrical distribution system is easy to understand when you understand how your circuit breakers interact. The main breaker provides the kill-switch safety measure to ensure that a branch breaker fault doesn’t overload the system. Take a look at your breaker box at home and you see how physical the electricity is which flows inside of your walls.

Even though it is rare, breaker boxes produce flashes and sparks, so always use the right safety precautions when you are working with electrics. And, always use tools and shoes with rubber surface covering. Rubber is non-electrically conductive and mitigates the flow of electricity through your body in the event of an accident.

If you like this article on understanding your main circuit breaker share it on social media. And check out the blog for more resources for home electrical issues. One final thought, this guide is for educational purposes only. We highly recommend that before you attempt to perform any electrical repairs on your own, please consult an electrician near you. Thanks for reading!

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