If you are designing a main electric panel for your factory or house then you must be wondering if you should use circuit breakers or fuses. Circuit breakers seem to be modern and are more convenient but can they replace fuses? I am going to address this question in this article and after reading it, you will be able to make your decision.
A Circuit breaker is a device that can mechanically break a circuit in the event of a short circuit. To be exact, a circuit breaker can break a circuit when the current flowing through it reaches a certain threshold or limit.
A fuse is an electric component or device that protects a circuit from overloading by breaking it upon reaching a certain current limit. Or in simple words, a fuse is a device that disconnects power to a circuit once the current reaches a certain limit.
I am listing a few pros and cons of circuit breakers and fuses in the hope to help you choose what suits you the best.
A Fuse or a circuit breaker, both have the same purpose which is to break the circuit as quickly as possible to avoid possible burning of equipment and wiring.
Circuit breakers are made using mechanical parts which move to break the circuit. This movement is usually achieved by using the magnetic field or thermal changes. The fault response time of a circuit breaker is usually around 10 milliseconds or more. It is good enough to prevent fires but when it comes to sensitive equipment, this time interval is too long and can easily cause severe damage.
On the other hand, fuses which we normally use in our houses are built to thermally burn to break the circuit. The burning time decreases as the current flow increases which is very beneficial. In the case of a short circuit, a large flow of current flow through the fuse which burns it far quicker than the tripping ability of a circuit breaker. An average fuse will only take 1 or 2 milliseconds to burn. This gives fuses an edge over circuit breakers. However, fuses do not instantly blow at slight overloads, for example, a 15A fuse will not quickly blow at 15.1A or even 16A. On slight overloads, it may take several seconds to blow. Usually, a non-delaying fuse will need double amps than its rating to blow instantly.
(Winner of this section updated in 2023: Circuit breakers win.The recent circuit breaker vs fuse test video our team made shows that modern circuit breakers can now outperform fuses in latency as well therefore we are updating this article. you can see the video are the end of this article.)
A fuse can only be used once and will need to be replaced after every fault.
Circuit breakers can be reset using a button after every overload or short circuit event. It is also much quicker to reset a circuit breaker using a button while it will take a few minutes or more to replace a fuse.
Winner: Circuit Breakers win here.
Circuit breakers are significantly costlier than fuses. However please keep in mind if you are expecting a lot of overload or short circuit events then the combined cost of fuse replacement can catch up with that of the circuit breaker.
Fuses are usually placed close to mains therefore changing a fuse is a bit risky task as it involves manual placement of fuse inside fuse box using hands.
On the other hand, a Circuit breaker can be easily reset using a button which is certainly less risky.
Winner: Circuit Breaker easily wins this round.
Fuses do not have moving parts therefore they do not fail while the most fearsome issue with a circuit breaker is the possibility of failures. Although it is very rare still sometimes circuit breakers fail to break circuits due to jamming of internal mechanical parts. It can result in the burning of an entire house or building.
Winner: To me, I think the main difference between a circuit breaker and a fuse is reliability therefore a low chance of failure makes Fuse a winner.
After going through all the above differences between fuse and circuit breaker, I think it is safer to conclude that fuse is more reliable while the circuit breaker is more convenient and easier to use; therefore, I recommend you to use a bit higher rated fuse along with a circuit breaker to have a perfect pair. This will give you all the benefits of circuit breakers along with the reliability of fuses.
Note: In case you are using fuse and circuit breaker together, you should make sure that your fuse has a higher amp rating than your circuit breaker. But it should not exceed your wiring’s maximum amp rating.
Here is a video that demonstrates the actual performance of a circuit breaker and fuse during a real short circuit event. This video also shows how dangerous a short circuit event can be without a fuse or circuit breaker.
Your fuse Amp rating should be in the middle of your calculated circuit breaker Amp rating and your wiring’s Amp rating. That way it acts as a failsafe in case your circuit breaker fails and will prevent your wiring from catching fire.
Remember! Never install an overrated fuse in your fuse box. It is your last line of defense against electric short circuits.
Every circuit can only handle a certain amount of current after which it will get damaged or can even cause damage to the surrounding area by burning itself and the things nearby. That is why we need to use a fuse in series when powering an electric circuit so that if the circuit malfunctions and tries to pull more than the allowed current, the fuse will burn and break the circuit.
For example, if you have used a cable in your house’s electric wiring that can handle a maximum 20A current but you mistakenly put a load of 30A or 40A on it then the cable can burn to cause a house fire. But if you had placed a 20A fuse in the series of your house wiring then even if you mistakenly put a 30A current on its wiring, the 20A fuse won’t allow the 30A current and will break the circuit by burning itself thus your house will stay safe.