How To Properly Fuse A Solar System

Home How To Properly Fuse A Solar System

Solar panels have recently become much more common as people all over the world begin to shift toward a greener and more sustainable way of life. Going off-the-grid requires some people to be able to do their own housework, and in circumstances like this, knowing how to correctly wire the solar panels is essential. 

In most cases, a solar system fuse is required between a solar panel and its charge controller because fuses and circuit breakers protect the wiring from overheating. This also avoids any appliances from catching fire or being damaged in the event of a short circuit. However, if the solar panels are wired in series, a fuse is rarely required.

What Is A Solar Fuse?

A solar fuse is a kind of fuse especially meant for solar power systems. This fuse solar protects the solar equipment against overheating, overloading, or short circuits that might occur. The solar fuse can be chosen based on several factors such as physical size and shape, amperage rating, breaking capacity, and many more.

What Type/Size Of Fuse Do We Need?

Fuse connector kit
Source: Pinterest

For photovoltaic (PV) systems to operate safely, dependably, and over the long term, the fuses must be properly sized. In contrast to customary electrical power distribution and control applications, solar system fuses are susceptible to special circumstances. Long-term exposure to environmental factors can lead to aberrant ambient temperatures, which in turn impacts conductor choices, sizing, and fuse performance. 

Additionally, PV modules produce continuous currents, unlike traditional circuits, which are typically sized based on continuous loads, necessitating additional considerations for sizing fuses. Given these circumstances, a special technique for sizing solar fuses in PV systems is required.

Where To Fuse?

A fuse holder
Source: Beny

There are three most common places where the fuse can be installed in the solar panels. The first is between the battery bank and the charge controller. Secondly, it can be placed between the charge controller and the solar panels. Lastly, the fuse can also be present between the inverter and the battery bank. 

The fuse between the charge controller and solar panel functions efficiently to protect against the overheating of wires while at the same time protecting the appliance against any damage. 

Tools Required 

Solar photovoltaic PV support system
Source: Pinterest
  • Angle finder
  • Torpedo level
  • Fish tape
  • Chalk line
  • Cordless drill (14.4V or greater), multiple batteries
  • Unibit and multiple drill bits (wood, metal, masonry)
  • Hole saw
  • Hole punch
  • Torque wrench with deep sockets
  • Nut drivers 
  • Wire strippers
  • Crimpers
  • Needle-nose pliers
  • Lineman’s pliers
  • Slip-joint pliers
  • Small cable cutters
  • Large cable cutters
  • AC/DC multimeter
  • Hacksaw
  • Tape measure
  • Blanket, cardboard, or black plastic 
  • Heavy-duty extension cords
  • Caulking gun
  • Fuse Pullers

How To Fuse A Solar System?

Solar panel fusing 

Solar panel fusing
Source: Pinterest

The commercial solar panels with over 50 watts utilize 10 gauge cables that can withstand the current flows of up to 30 amps. In such instances, fusing is not a necessity if the panels are interlinked in the series. For instance, if there are four panels, each rated for 15 amps, a short in one of them could cause all 60 amps to be directed at the shorted panel. This will result in the wires leading to that panel receiving significantly more current than 30 amps, potentially causing that wire pair to catch fire. 

Fusing for a parallel/combiner box

600V CD Combiner Box
Source: Beny

A combiner box is used in a parallel system to contain the fuses and breakers for each panel as well as one or more “combined” fuses that connect to the charge controller or grid tie inverter. We must first calculate the worst-case current that will flow based on our unique panels before sizing this “combined” fuse/breaker.

Charger to Battery Fuse or Breaker

Battery Fuser
Source: Pinterest

Because the worst-case amps flowing to and from a Pulse Width Modulated (PWN) charge controller is the same, the fuse and wire size can match. Contrarily, MPPT charge controllers have the capacity to both reduce voltage and increase the current flowing between the controller and the battery bank, necessitating a recalculation of the exact size of the wire and fuse or consulting the charge controller manual. For their Solar Boost 50 (amp) charge controller, for instance, Blue Sky advises installing a 60-amp fuse/breaker between the device and the battery bank. Once more, pick a wire with the correct rating.

Situations You Do Not Need To Fuse

Solar panel Parallel Fuse Connectors
Source: Pinterest

The solar array does not need to be fused if the short circuit current of the solar array is less than the maximum series fuse rating of the solar panel. Because of the following, there is no added protection or benefit by fusing this kind of array:

Three 200W panels are connected in sequence. Each solar panel has a maximum series fuse rating of 15A and a maximum series short circuit current of 10.2A, 9.8A, and 9.8A, respectively.

Given that the maximum series fuse rating is 15A, we can assume that the internal wires, diodes, connections, and other parts of the real solar panel can withstand a maximum current of 15A.

Since the array’s short circuit current is 10.2A, it is reasonable to state that if a short circuit or other malfunction were to occur within one of the solar panels, the panel would be equipped to manage the situation because the short circuit current cannot surpass the panel’s maximum fuse rating.

It will ultimately never permit the fuse to blow. Make the fuse endure bothersome blows on a constant basis when it is performing normally. Due to this, a fuse is not necessary for this situation, according to code.


Any solar panel system that includes a fuse between the panels and the charge controller is highly advised since it will shield electrical appliances and gadgets from power surges and keep the wires from overheating or catching fire as a result of an overcurrent. Even though a smaller PV system with panels connected in series may not require a fuse, it is always advisable to be safe than sorry. A fast-blow fuse is the safest option for the system. Refer to Beny for better solutions for solar power systems. 

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