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Solar Fuse Vs. Breaker: Which One Should You Use?

Solar fuse placement in a solar system
Solar fuse placement in a solar system
Resource: https://www.cruisersforum.com

Solar fuses and circuit breakers are both protective devices for electrical systems, but which one is better for your solar system? In this comparison of solar fuse vs. breaker, we’ll help you understand the major differences between the two devices. After that, we will give our verdict as to which one is better for solar systems.

To start us off, here is a quick definition of each device:

What is a Solar Fuse?

A solar fuse is a type of overcurrent protection device that is specifically designed for solar PV systems. It’s commonly used on the DC side of the system, but can also be used on the AC side and rated for AC currents.

Usually, fuses for solar system protection are sized in terms of their amperage and voltage. For example, a 10A, 600V solar fuse can safely interrupt a 10A current at up to 600V, while a 20A, 1200V solar fuse will interrupt a 20A current at up to 1200V.

It’s also common practice to size solar fuses at 1.25 times the rated current of the specific circuit. For example, if a circuit is rated for 15A, then a 20A solar fuse would be used.

What is a Circuit Breaker?

A circuit breaker is an electrical switch that automatically opens (and sometimes resets) a circuit in the event of an overload or short circuit.

Like fuses for solar, these circuit breakers are designed for use in photovoltaic (PV) systems. They are available in both DC and AC versions, but DC-rated solar circuit breakers are more common.

Solar circuit breakers are rated in terms of their amperage, voltage, and interrupting capacity. More importantly, the breakers will contain a means of handling the stubborn arcing of DC circuits.

Solar circuit breaker or resettable solar fuse
Solar circuit breaker or resettable solar fuse
Resource: https://www.youtube.com/watch?v=z4ugx9WW-sI

Solar Fuse vs. Breaker

Now, on to the solar fuse vs. breaker dilemma and which one you should use in your PV system. First is a look at the main differences between the two devices. After that, we’ll see what is better for solar.

Solar Fuse vs. Breaker: Working

A PV solar fuse works by melting a conductor when the current flow through it exceeds the rated value. This interruption of current flow protects the circuit from further damage. In other words, it’s a sacrificial device – once the fuse melts, it needs to be replaced

On the other hand, circuit breakers generally use electromagnets, bi-metal strips (or both an electromagnet and bi-metal strip), or they can be electronic. This allows the circuit breaker to be reused after it has been triggered.

Solar Fuse vs. Breaker: Installation

Solar fuses are generally easier to install than circuit breakers, especially when it comes to retrofitting an existing system. This is because solar fuses don’t require any special wiring – they can simply be connected in line with the circuit or inserted into a solar fuse holder.

Circuit breakers, on the other hand, need to be mounted onto a panel or some other type of support, in addition to requiring some wiring. This can make installation more difficult, especially in systems where you need several installed.

Solar Fuse vs. Breaker: Response Time

The response time of a fuse, whether solar battery solar fuse, panel protection fuse or other type, is typically faster than that of a breaker (around 0.002 seconds).

This is because the fuse uses a simple melting mechanism to open the circuit, while most circuit breakers use a thermal mechanism, which can take slightly longer to respond.

In contrast, most breakers have a response time of around 0.02 – 0.05 seconds. In cases where fast response is critical, such as in short-circuit protection, fuses may come out as better protection devices. In some applications, though, the breaker delay also prevents unnecessary tripping and downtimes.

Solar Fuse vs. Breaker: Maintenance

Solar power fuses may appear to require more maintenance than breakers (they need to be replaced every time they “blow”). However, when rated correctly, a solar fuse in a PV system will rarely “blow.”

If they did, the solar fuse replacement cost would start to add up, and the inconvenience of having to replace them would be a hassle. In these cases, circuit breakers would be a better choice.

That said, it’s good to note that DC arcing can take a toll on breakers, causing them to wear sooner than expected and making properly sized fuses a better option for most solar installations.

Solar Fuse vs. Breaker: Cost

The solar fuse price is normally much lower than that of the circuit breaker price for the same amperage and voltage rating. This is because solar fuses are less complex than circuit breakers, and can be mass-produced more easily.

DC current circuit breakers, in particular, are usually more expensive than their AC counterparts. This is because they normally come with the ability to handle the arcing that is common in DC circuits or systems.

 Solar fuse box with the fuses installed
Solar fuse box with the fuses installed
Resource: https://youtu.be/vAGEeRt-L6E

Solar Fuse or Breaker?

Now onto the big question: Which one, between a solar fuse vs. breaker, is better for a PV system? The best answer, as with most things, is “it depends”, and one can use either. With that said, these points will help you make a decision:

  • If cost is your primary concern, then you may want to go with fuses. They cost less upfront.
  • If ease of installation is necessary (you are a DIY-re), then opt for fuses. They are easier to install and DIY-friendly.
  • If response time matters much, then go with fuses. They have a faster response time than circuit breakers.
  • If you want the convenience of being able to reset the device in the event of an overcurrent, then a breaker is the better choice. Breakers can also be used repeatedly, plus they can also act as isolation devices.

While both devices have their own advantages and disadvantages, the decision of whether to use a fuse or breaker in your solar system ultimately comes down to personal preference.

In general, though, fuses – whether PV string fuses or battery protection fuses- are better for small systems and circuit breakers are better for large systems. They’re also generally better for short-circuit protection, while breakers offer more flexibility and conveniences for larger installations

Besides, breakers can wear quickly when used in the DC circuits of a solar system. This usually happens because of the DC arcing that occurs when the breaker trips.

For that reason, many solar PV systems use a combination of solar system fuses and circuit breakers, with fuses being used mostly on the DC side and breakers on the AC side. This provides the best protection for the system while still keeping costs down

Conclusion

As a solar system owner, it’s upon you to make sure that your assets are protected against damage. That means using either solar PV fuses or breakers to protect your system against any potential electrical problems. Some people opt to use both, while others use just one or the other.

The bottom line is that it’s up to you to decide which device will work best for your system. Just make sure to do your research and choose the option that will provide the best protection for your solar PV system.

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