Considerations for Using Circuit Breakers as Disconnect Switches

We’ve often been asked if circuit breakers can be used as system disconnects in police cars and other vehicles with a large number of electrical accessories. Although using a circuit breaker this way may seem practical or cost-effective, it’s important to be aware of certain risks since most circuit breakers have not been designed for routine On/Off use.

In many cases it makes best sense to install a battery disconnect switch for shutting down system electrical power in a vehicle. However, some circuit breakers are available that have been designed to handle On/Off switching. Let’s explore the options.

Battery Disconnect Switches
Incorporating a battery disconnect in the electrical system enables operators and technicians to shut down a vehicle's power quickly and easily. By cutting off power at the battery, the vehicle is rendered inoperable, ensuring safety for officers, technicians, first responders, and others. It also helps prevent theft or unauthorized use of the vehicle, and prevents battery drain when the vehicle is not in use.

You can see a broad selection of vehicle battery disconnects on the Waytek website.

Right: The Cole Hersee Master Battery Disconnect, a small, easy-to-install option that provides effective power cut off to ensure safety during emergencies and prevent battery drain when a vehicle is not in use.

Circuit Breaker Considerations
Circuit breakers are designed to cut off power to an electrical circuit when a fault or overload is detected. Although ideal for their intended purpose, most thermal DC circuit breakers are not suitable as a main branch cut off.

Depending on a vehicle’s wiring design, a circuit breaker may not ensure complete shut-down of all of the vehicle accessories. If your goal is to eliminate battery draw, flipping a circuit breaker may not do the trick.

Another reason why a circuit breaker may not be suitable for main branch cut off is its capacity. Many thermal automotive DC circuit breakers are rated for low current (50 amps or below), which is not appropriate for handling main branch current.

But even higher amp circuit breakers are not typically designed for main branch cut off. If you intend to use a circuit breaker as a disconnect, your best option is to look at high-amp circuit breakers that are marine-rated.

Marine-Rated Circuit Breakers
Marine-rated circuit breakers have long been built to meet exacting standards required by the marine industry – including the ability to function as both a circuit breaker and a main branch disconnect. Because of their high-performance capabilities, they also have a growing track record of use in vehicles and other electrical systems.

Two leading examples are Eaton’s Series 187 circuit breakers (below, left) and Mechanical Products’ Series 87 circuit breakers (below, right). If you intend to use a circuit breaker as a disconnect, be sure to consider these two product lines.

 

                                 

 

Another interesting option is the Series 53 Branch Disconnect from Mechanical Products – a “two-in-one” product that contains both a circuit breaker and an on/off switch in one space-saving component (photo below).

Although originally designed for use in the marine industry, all the marine-rated circuit breakers discussed above can be utilized in police vehicles, work trucks, and other vehicles requiring an ability to quickly disconnect the electrical system when a vehicle is not in operation.

Check Your Specs
Whether you decide to use a disconnect switch or a marine-rated circuit breaker for main branch cut off, be sure to check the manufacturer specifications to make sure the component can handle the requirements of your vehicle’s electrical system.

Learn more about battery disconnect switches and marine-rated circuit breakers from Eaton and Mechanical Products on the Waytek website, and feel free to contact us if you have any questions.