Absolutely Everything You Need to Know About a Thermal Magnetic Circuit Breaker

Do you know how a thermal magnetic circuit breaker works?

If not, it’s worth finding out as these popular options are probably going to be the best bet for your home or building.

How a Thermal Magnetic Circuit Breaker Works

Despite the name, it’s actually fairly easy to understand how a thermal magnetic circuit breaker works. You just have to understand how two other versions operate first.

How a Magnetic Circuit Breaker Works

The main difference between these two circuit breakers comes down to what makes them trip. In other words, the difference is in how they protect the home/building’s wiring.

In a magnetic circuit breaker, this is done with an electromagnet.

When an acceptable amount of current is throwing through the breaker, the electromagnet is unaffected. It’s calibrated to move the trip bar when sufficient magnetic force – via a strong enough current – is present.

As the current increases through the coil, it could eventually reach a threshold where it becomes powerful enough to pull the trip bar toward the electromagnet. This would open the contacts and stop the current.

In doing so, it prevents significant damage from occurring – including a fire.

Magnetic circuit breakers shut down immediately when the current becomes too powerful. The moment the magnetic current becomes strong enough, it automatically pulls the trip bar.

How a Thermal Circuit Breaker Works

A thermal circuit breaker accomplishes the same thing by using a bimetallic strip.

Again, as the current builds in power, it becomes hotter and hotter.

At some point, the temperature reaches a predetermined threshold for the breaker and actually damages the bimetallic strip to the point that it gives and breaks the connection.

Fortunately, when it cools down, the strip is able to be reset and normal operation can continue.

Unlike the magnetic version, a thermal circuit breaker works on a time delay. The heat must build until it is able to deform the strip enough to shut down operation.

How a Thermal Magnetic Circuit Breaker Works

As the name suggests, a thermal magnetic circuit breaker works by combining the two versions above.

It essentially leverages both forms to protect the conductors and other elements connected to the circuit breaker from the dangers of excessive current.

The main advantage of how a thermal magnetic circuit breaker works is that it gives you both instantaneous and time-delayed protection.

Instantaneous protection is good for interrupting currents that are extremely powerful but not part of normal operation, like line-line faults, line-ground faults, and short circuits. They must be interrupted right away or they could become dangerous, even fatal.

So why would you ever want a delayed response?

Some pieces of electrical equipment temporarily draw currents that exceed their rated values. This is part of their normal operation. Examples of this type of equipment include electric motors and HID lamps.

When started, they can pull extremely high inrush currents.

A magnetic circuit breaker would not allow this initial requirement, so these devices wouldn’t work.

Choose a Thermal Magnetic Circuit Breaker

The advantages of relying on a thermal magnetic circuit breaker should be fairly obvious. In short, they will keep your home or building safe without limiting the types of devices you can use. Given their popularity, you’ll also have no problem finding one that fits your unique needs.