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Difference Between Isolator Switch and Circuit Breaker

Isolator switch
Isolator switch
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The difference between isolator and circuit breaker may not be clear to everyone. To shed light on why the two devices are not interchangeable, we compared their unique features and technical properties in this — not only that but also their functions and where to use each, among other facts.

Isolator Switch Meaning

An isolator switch is a manual device that’s installed in an electrical system to provide a way to disconnect or isolate a circuit. The isolator normally used as an on/off switch and creates a single point in which electricity can be controlled.

Isolator switches are not designed to break short circuits though, unless fused. They are, therefore, not to be used as overcurrent protection devices. Instead, they isolate a circuit that has been disconnected by other means, such as a circuit breaker or fuse.

A typical isolator is a single or multi-pole switch contained in a robust enclosure, and used to make sure no current can flow in a circuit, when the switch is open. This ensures safety for maintenance personnel and other people working with the installation.

Circuit Breaker Meaning

A circuit breaker is an automatic device used to protect the electrical system from overcurrent or short circuits. It works by disconnecting the circuit when a predetermined current limit is exceeded, thereby preventing further damage due to excessive currents in the wiring.

Circuit breakers, unlike the electrical isolator switch, are designed to trip and reset after a short circuit or overcurrent situation has been cleared, so they can. This allows power to be safely restored in the event of an electrical fault or emergency.

It’s good to note that both circuit breakers and isolator switches are meant for use (and installed) in the same system, with the breaker coming before the isolator. That way, the isolating device serves to provide an additional layer of safety and protection

Inside an isolator switch box
Inside an isolator switch box
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Isolator Switch vs. Circuit Breaker

The main difference between an isolator switch vs. circuit breaker is their purpose: isolator switches are used to manually disconnect or isolate a circuit, while circuit breakers act as overcurrent protection devices. Other features that further explain the difference between isolator switch and circuit breaker are given below.

Isolator Switch Rating

Being on/off devices, isolator switches are rated lower for withstand current than breakers or breaking capacity. Unlike isolator switches, circuit breakers are designed to protect electrical circuits from overcurrent and short circuits.

Thus, they come with higher ratings for current withstand capacity. The isolator rating is an important factor when installing the device, just as, just as with other electrical components.

Isolator Switch Operation

As stated earlier, isolator switches are manual devices that require user interaction to operate. Most often, they are manually opened and closed when needed, although motorized mechanisms are available for higher voltage applications.

The isolator is also a simple on/off switch, with no complex parts; only the contacts and their insulation are present. Contrary to the isolator switch operation, circuit breakers are an automatic device that trips autonomously when a pre-defined current limit is exceeded.

Breakers are also more complex in construction than isolators with different parts such as the trip coils, bimetallic strips and other components which work to detect any changes in the current. In other words, they use multiple mechanisms to operate.

Isolator Switch Function

Another major difference between isolator switch and circuit breaker is their fundamental function. The primary purpose of an isolator switch is to completely disconnect a circuit for safety or maintenance purposes, allowing the user to work on it without the risk of electrocution or further damage to equipment.

On the other hand, circuit breakers are designed to protect electrical circuits from overcurrent and short circuits. Circuit breakers also disconnect circuits for safety, but with aim to prevent overheating and fire hazards due to an overload in current.

Isolator Switch Contacts

In addition to the difference in ratings and function, the contact materials of an isolator switch differ from circuit breakers. Isolator switch contacts normally consist of main and moving contacts but no arcing protection. This is because the isolator is usually used in the no-load condition.

On the other hand, breakers come with arcing contacts. These draw and contain any arcing that may occur when the breaker trips, thereby preventing damage to contacts and other components in the circuit.

Isolator Earth Switch

An earth switch is normally used with an isolator switch. The isolator earth switch is crucial feature that provides an additional level of safety when disconnecting circuits from the power source. It grounds the isolated circuits, thereby dissipating any remaining charge before anyone can come into contact with the equipment.

In contrast, circuit breakers have trip circuits that detect any changes in the current. You do not use an earth switch with circuit breakers. This is because the trip circuit will detect any changes in the current and trip the breaker autonomously.

Isolator Switch Cost

Isolator switches are typically less costly than circuit breakers for devices rated for similar electrical systems. The lower isolator switch cost is mainly attributable to the fact that they do not contain many parts, which translates into fewer costs associated with the manufacturing process.

Because they are not designed to handle overcurrents and therefore, don’t need specialized components like trip coils and bimetallic strips that must be present in order for a circuit breaker to function correctly.

Circuit breakers are more expensive as they come with components that allow them to detect and trip under excessive currents. In addition, they are also able to provide protection to the electrical circuits from short-circuits which isolators cannot do.

Isolator Switch Installation

The isolator switch installation procedure and requirement is also different. In terms of location, isolator switches are usually installed in places where they can be used to manually disconnect the power source, but not before the circuit breaker has been disconnected by the breaker itself.

That’s because an isolator is to be use in a no-load condition, where there’s no risk of electrical arcing or further damage to the equipment. In comparison, a circuit breaker is used to protect against overload, and so should be installed (and used) in the path of the current.


The isolator and circuit breaker difference can be seen in many aspects, from ratings and function to contact materials and costs. Overall, the main difference between them is their purpose; isolator switches are designed to provide complete electrical isolation whereas circuit breakers protect against overcurrent conditions.

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