how do circuit breakers workCircuit breakers protect your home and electrical system. Modern houses draw a lot of electricity. When their circuits are balanced, energy flows smoothly from the electrical panel to your appliances and then back to the source.

However, when a circuit draws excess current, it begins to overheat. In most cases it melts, destroying your wiring and the appliances connected to it. In the worst cases, it catches fire. Circuit breakers exist to prevent this kind of damage. But how do circuit breakers work? How do they safeguard your home’s electrical system?

How Home Circuitry Operates

When connected to the power grid, your home wiring forms a large electrical circuit. It contains one set of wires (hot wires) that brings electricity into the house and another set (neutral wires) that returns it back to the source.

Every room in the house is broken down into separate circuits that repeat this pattern, with hot wires and neutral wires circulating electricity through your appliances. All these circuits are connected through your electrical panel, which controls the flow of energy through your home.

Where Circuit Breakers Fit In

To answer the question of how circuit breakers work, you need to understand the basic components of electrical capacity: volts, amps, and watts. Volts are the pressure that makes electricity flow through a conductor (e.g. a wire). Amps are the number of electrons being pushed through the conductor at any given moment. Finally, watts are the total electrons used to power an electrical device.

Volts, amps, and watts are interconnected. Multiply amps and volts to get watts. Divide watts by amps to get volts. Or divide watts by volts to get amps. Put another way:

  • Volts x Amps = Watts
  • Watts/Amps = Volts
  • Watts/Volts = Amps

Every conductor resists electrical current to some degree. This means that every circuit has a maximum wattage (i.e. load) it can carry. A 20 amp, 120-volt circuit can only carry 2,400 watts, though to be safe, electricians recommend circuits never exceed 80 percent of their capacity.

In order to imagine the danger of exceeding a circuit’s maximum load, consider what happens when you plug a 10W light bulb into a 50W socket. Light bulb filaments glow because they resist electricity. In fact, the more electricity you run through them, the brighter they glow until suddenly the filament burns up. The same thing happens when you draw 3,000 watts through a 2,400W circuit. Like filaments, wires also resist electrical current. Pump too much in and eventually, they overheat.

How Circuit Breakers Work

Circuit breakers are an integral part of your electrical panel. They’re made from insulated plastic, with two terminals that conduct electricity into your home. Inside are two contact plates: a stationary plate and a moving plate. The stationary plate is connected to the frame, while the moving plate is connected to a metal arm called an actuator.

When these plates are together, they complete the circuit. When they’re apart, they break it, stopping the flow of electricity. In a magnetic circuit, the actuator is controlled by a magnet, which charges as current flows through the circuit breaker.

As long as the current is below the circuit’s maximum load, the magnet never becomes strong enough to trip the actuator. However, when the load exceeds the circuit’s maximum capacity, the magnet turns the actuator, which rotates on a pivot and pulls the contact plates apart.

In a soldered circuit, the actuator is controlled by a block of alloy (solder) made from two metals with different coefficients of thermal expansion (i.e. they expand at different temperatures). As the current flows through the actuator, it heats the solder. When it reaches maximum load, the solder expands, but because of the difference in thermal coefficients, it bends, turning the actuator and interrupting the circuit.

Unlike fuses, which burn out when they trip, a circuit breaker can be reset after it cools down. However, it’s always a good idea to disconnect a few appliances in the room that tripped it, otherwise, the circuit’s likely to trip again. If the circuit trips again anyway, call an electrician. You may be dealing with a short circuit, ground fault, or arc fault.

Protecting Your Home’s Internal Wiring

Repairing your electrical system can be expensive. Rewiring a house can cost the average homeowner up to $10,000. Make sure you’re protected in case of a serious fault or short circuit. Homesential covers circuit breakers, breaker panels, switches, and outlets at almost no cost. For less than you spend each day on a cup of coffee, you can rest easy knowing we’ve got your back in case anything goes wrong. Contact us today and find out how much you can save!