Created by: Glen Zhu | Updated Date: Feb 23, 2023
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.
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.
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.
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.
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:
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.
Does a surge protective device need a dedicated circuit breaker or fuse?
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:
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.
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.
We’ll show you how to install it at single and three phase power supply system.
To learn more about correct surge protective device installation and wiring diagram, please visit our webpage: https://lsp.global/surge-protective-device-installation-and-wiring-diagram/
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)
63A or 100A
32A – 40A
20-40kA (Type 2)
20-50kA (Type 2)
7kA (Type 1)
20-50kA (Type 2)
12,5kA (Type 1)
25-100kA (Type 2)
25kA (Type 1)
To learn more about coordination between surge protective device and its disconnect circuit breaker (or fuse), please visit our webpage: https://lsp.global/surge-protective-device-coordination/
A new product to replace dedicated MCB or Fuse, it is 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.
Installing an SCB (Surge Circuit Breaker) in the front end of SPD (Surge Protective Device) can solve four problems at the same time:
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.
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.