Surge Protection Circuit Breaker

Surge Protection Circuit Breaker

Created by: Glen Zhu | Updated Date: Feb 23, 2023

Surge Protective Device and Circuit Breaker

Surge Protection vs Circuit Breaker

Circuit breakers and surge protectors protect against two different things, you need both. Actually circuit breakers in the panel aren’t even expected to protect what is plugged into a circuit, for that you need a properly sized circuit breaker or fuse at the device, and a surge protective device.

What is Surge Protective Device?

Surge protective device (SPD) is a protection device designed to prevent various electronic equipment, instruments, and communication lines from being subjected to surge shocks (such as lightning strikes).

Surges happen when lightning strikes power lines or during sudden connection or disconnection of power lines at the electric supply network.

They’re way too fast and furious to trigger a fuse or an MCB, so be protected with a surge protection device when a surge strikes.

When the electrical circuit or communication line suddenly generates a peak current or voltage due to external interference, the lightning surge protection devices (SPDs) can conduct and shun the current in a very short period of time, thereby avoiding the damage of the surge to other equipment in the circuit.

Surge protectors protect electrical equipment from power surges, by absorbing or redirecting the power surge to earth before it reaches the protected equipment.

The surge protection devices mainly prevent the sudden high voltage in the circuit. When the sudden high voltage appears, the surge protector behaves as a short circuit and releases the excessive voltage to the ground, thus protecting the electrical equipment.

Surge protective devices protect your electrical appliances from voltage spikes. SPDs aren’t mandated by state or community regulations but are highly recommended.

What is Circuit Breaker?

A circuit breaker is a mechanical switching device that can make, carry and break current under normal circuit conditions.

Circuit breakers are used to protect electrical circuits from damage caused by overloading or short circuits or a ground fault. When the current exceeds the rated current, it starts to cut off the circuit to protect the electrical equipment.

Miniature circuit breakers are the most widely used terminal protection appliances in building electrical terminal distribution devices. It is used for short circuit, overload and overvoltage protection of single-phase and three-phase below 125A.

A circuit breaker has a limited response time, a few milliseconds, and it is best to describe it as an off-switch that reacts to over-current. A fuse serves the same function as a circuit breaker but requires replacement after a short circuit.

While a circuit breaker is still there to protect your home from electrical issues, the exact kind of electrical issue and how it functions is very different from the surge protector.

What’s the difference between Surge Protective Device and Circuit Breaker?


Surge protection devices protect only from surges, that is over-voltage spikes and for short periods, milliseconds, whereas circuit breakers protect against over-current in a circuit or house wiring.

While circuit breakers protect wires from starting a fire due to too many amps (amount of electrical current), surge protective devices protect your appliances from power surges, which is a brief spikes in voltage (electrical power or force).

Surge protective device and circuit breakers both cut off power during exceptional conditions, but they have different purposes and react to different events:

Circuit breakers have only one job: to prevent the wiring inside your house from catching on fire. That’s it, they do nothing else. They don’t protect you from shocking yourself, or from lightning, or from your cat chewing through a power cord.

A surge protective device is designed to protect an appliance against voltage spikes, whereas a circuit breaker will protect your home’s electrical system from high currents and potential fire.

A circuit breaker is usually installed in your home’s main electrical panel. At the same time, a surge protector is generally built into a power strip, although you can also have a ‘house surge protector’ installed in your main/sub-power boxes.

A circuit breaker is mandatory for home electrical safety, whereas a surge protection device is optional and can provide peace of mind.

So as you can see, they both offer protection, but in different ways. Surge protection device (SPD) protects from a surge of volts, whereas a circuit breaker protects from an overload of amps.

The Basics of Type 2 Surge Protective Device

A commonly used technology in Type 2 SPDs is the metal-oxide varistor (MOV) type. The way such devices work is that they act as an open circuit at normal voltages and start conducting at high voltages (like those encountered during a surge) to safely dissipate the surge energy to the earth, thereby protecting the circuit and the loads.


The SPD would need to be replaced once the cartridge reaches end-of-life. This is dependent on both age as well as number of surges that has hit it. There are broadly two ways in which the SPD reaches end-of-life:

Thanks to pluggable cartridge for easy replacement when failing without shutting down the power
The working principle of surge protector
  • Thermal disconnection – where after protecting against several surges the leakage current through the MOV increases and heats it. At this time a fusing element disconnects the MOV from the system.
  • Short-circuit failure – where the device was subject to surges greater than design capacity or was subject to continuous over-voltage.

Well-designed products have a visual indication that shows that the SPD needs to be replaced.

Some products are available in a pluggable form where only a cartridge needs to be replaced.

Some products also come with a remote indication contact which can be used to trigger an alarm, although these are generally used more in industrial applications where continuity of service is more critical.

One thing to remember is to always use a backup short-circuit protection device (like an MCB or a fuse) along with the SPD. This ensures the safety of system.

The Basics of Using Circuit Breakers with Surge Protectors

Does a surge protective device need a dedicated circuit breaker or fuse?

In the electrical profession, questions still arise about what type of circuit breaker to use with surge protectors. It’s necessary to choose the right dedicated circuit breaker coordinated with the panel’s main breaker or panel’s upstream breaker.

Essentially, the circuit breaker must be sized to the surge protector’s wire size and the electrical panel’s ratings. For example, a surge protector with 6-10mm2 wires should be used with a breaker rated at 32A. The circuit breaker’s ratings (interrupt rating, voltage rating) must also be suitable for the panel. Of course, to be 100% sure, follow the surge protection devices (SPDs) manufacturer’s installation instructions.

A stand-alone or dedicated circuit breaker for surge protector performs the following functions:

  • Allows power to the surge protector to be removed without interrupting power to other loads.
  • If a component fails inside the protector, only the circuit breaker will trip, and the power of any other load will not be disturbed.

Do circuit breakers protect against power surges?

Absolutely not.

Does a SPD need a dedicated MCB?

In certain surge protector applications, a stand-alone circuit breaker is needed to ensure a safe and reliable system. A stand-alone breaker is one that is not part of the load center.

Quality circuit breakers work well with surge protectors and provide an extra measure of safety and convenience.

Does a surge protector prevent tripping circuit breaker?

If the SPD fault, the panel’s main breaker or panel’s upstream breaker can’t trip, the dedicated circuit breaker which installs before SPD will trip.

Surge protective device before or after breaker?

Take an electric power supply system for example, when inserting a surge protective device in the system, it needs a stand-alone or dedicated circuit breaker for this SPD.

How to properly install a dedicated MCB for a surge protective device?

We’ll show you how to install it at single and three phase power supply system.

Wrong installation

Single Phase Energy Meter Connection Wiring Diagram Installation with Surge Protection Device SPD without a dedicated MCB Circuit Breaker

Correct installation

Single Phase Energy Meter Connection Wiring Diagram Installation with Surge Protection Device SPD with a dedicated MCB Circuit Breaker

Wrong installation

Three Phase Energy Meter Connection Wiring Diagram Installation with Surge Protection Device SPD without a dedicated MCB Circuit Breaker

Correct installation

Three Phase Energy Meter Connection Wiring Diagram Installation with Surge Protection Device SPD with a dedicated MCB Circuit Breaker

To learn more about correct surge protective device installation and wiring diagram, please visit our webpage:

How to match a surge protective device with a circuit breaker?

We list a table as a general reference about how to match a SPD and MCB, it needs a concrete analysis of specific situations.


Main Circuit Breaker

Dedicated Circuit Beaker

Surge Protective Device

SPD Selection Reference


< 40A or 63A

20A – 32A

10-20kA (Type 2)

SLP20 series


63A or 100A

32A – 40A

20-40kA (Type 2)

SLP40 series




20-50kA (Type 2)

7kA (Type 1)

FLP7 series




20-50kA (Type 2)

12,5kA (Type 1)

FLP12.5 series




25-100kA (Type 2)

25kA (Type 1)

FLP25 series

Coordination between surge protective device and its disconnect circuit breaker (or fuse)

To learn more about coordination between surge protective device and its disconnect circuit breaker (or fuse), please visit our webpage:

Surge Circuit Breaker

A new product to replace dedicated MCB or Fuse, it is SCB – Surge circuit breaker.

Why SCB - Surge Circuit Breaker?

The mismatching between surge protection devices and fuse or breaker. SCB successfully solved the problem of surge protective device failure ignition trip.

The traditional method is to link a fuse or breaker in series in front of lightning protection devices, there would be four mismatching aspects if doing so.

  1. When lightning protective devices degrade or there is overvoltage occurring in the distribution circuit, lightning protective devices will become short-circuited to grounding and Fuses or breakers can’t disconnect quickly.
  2. When lightning occurs, fuses or breakers can’t stand the temporary energy of lightning current, for they were used as components of power distribution in the early design. So it is easy to cause them to trip or explode, making lightning protection ineffective.
  3. When lightning currents go through breakers, the Up value is very high and lightning protective devices can’t protect equipment well.
  4. Fuses or breakers can’t disconnect in the power installed line of the transformer. When a short circuit takes place, it can’t break quickly.

Where does SCB install?

Installing an SCB (Surge Circuit Breaker) in the front end of SPD (Surge Protective Device) can solve four problems at the same time:

  1. When lightning protective devices degrade or there is overvoltage occurring in the distribution circuit, SCB can disconnect quickly to avoid lightning protective devices from Firing. The breaking current is less than 3 A.
  2. When the lightning current goes through, the Surge Circuit Breaker linked in series in front of SPD can keep no tripping and no damage under the lightning current of 100kA, keeping the SPD in working order.
  3. When the lightning current goes through SCB, the Up value is very low, equal to copper with the same length.
  4. The breaking capacity of SCB exceeds plastic breakers, up to 100kA.

Working principle

A Surge Circuit Breaker (SCB), the exclusive external disconnector of SPD, is a kind of equipment that is developed according to article 430.3 in the IEC61643-4-43: adopt suitable over-current protection devices before dangers are caused by a circuit.

It mainly solves problems that when following currents or leakage currents take place in SPD, SCB can trip quickly, while lightning currents pass, Surge Circuit Breaker does not trip, SCB ensures that SPD does not cause a fire and the lighting protection of equipment lasts long, solving the problems that there is protection blind in current widely used fuses and breakers which are used as external disconnectors.

Surge Circuit Breaker is the ideal matching device of voltage switching type SPD, and voltage limiting type SPD used in low-voltage power supply systems.

Product Usage

  1. Selective disconnection of the passed power frequency current and lightning current can effectively protect the SPD from short-circuiting and short-circuiting of SPD due to abnormal transient over-voltage, resulting in serious fire accidents.
  2. The selective division of the passed power frequency current and lightning current can effectively protect the SPD from causing the SPD starting voltage to drop below the power supply voltage, and the power frequency leakage current increases, causing a serious fire accident.
  3. When the SPD has lightning current, the external disconnector will not be accidentally tripped, so that the lightning protection of the electrical equipment is always in an effective state.

Scope of application

The Surge Circuit Breaker dedicated backup protector provides professional backup protection for the SPD (Surge Protection Device) that protects the power supply of the first, second and third levels.

Applicable to places where SPD lightning protection equipment has been installed, such as power equipment for industrial and civil construction, electrical, communications, road transportation, petrochemical and other industries.

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