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June 17, 2024

Solar Learning Centre

What Are Arc Faults in a Solar System?

Two exposed electrical wires with sparks in between, illustrating an arc fault. The text above reads, "What are Arc Faults?" with a logo in the bottom left corner.

Most homeowners shopping for solar are unaware of the risks associated with arc faults. The phrase itself is a little weird and doesn’t really describe what is to the average customer.

There are character arcs, the Arc of the Covenant, and the different types of arcs you’ll find with a protractor. None of those seem to be a threat to solar systems nationwide.

What is an arc fault?

At Penrith Solar Centre, we’re experienced in installing and maintaining solar systems. We are well-versed in the potential hazards associated with it. We’ve seen the effects of arc faults and understand the importance of proper system design (and the importance of choosing a safe solar system).

In this article, we will delve into the causes of arc faults, how they affect your solar system, and the steps you can take to prevent them.

You’ll learn the following:

  • What is an Arc Fault in Solar Systems?
  • How Do MC4 Solar Connectors Keep My System Safe?
  • Microinverters Are a Safety Solution

By the end of this article, you will have a clear understanding of how to invest in a solar system that will ensure the safety of your home.

What is an Arc Fault in Solar Systems?

An arc fault occurs when electricity discharges powerfully between two or more conductors when there’s space between them. This discharge produces heat that can degrade the wire’s insulation and start an electrical fire. Things like loose wires, gaps, or moisture can cause arc faults.

When an arc fault jumps from one conductor to another, it has the potential to start an electrical fire in solar systems.

There are two main types of solar systems have different types of electrical architecture. String inverter solar systems utilise high voltage direct current (DC) power and microinverters utilise alternating current (AC) power.

The arc faults that happen in a system with high voltage DC power are more dangerous. Higher voltage leads to bigger arcs (which are kind of like sparks), which have the potential to catch fire more easily. Lower-voltage AC power systems don’t have this issue.

Take a look at the following video. AC arc faults self-extinguish before they cause a fire.

As you can see, the high voltage DC power created a hot, sustained arc that could easily start a fire.

Even a minor equipment malfunction, like a frayed cable or a loose electrical connection, can trigger a DC arc fault, potentially causing an instant and intense fire.

The AC arc fault, on the other hand, only made a brief, small arc that extinguished itself quickly. This difference is crucial for safety.

DC arc faults can reach temperatures of up to 1,085°C. They can easily melt materials like glass, copper, and aluminium.

All solar system fires are caused by DC arc faults, which only occur in string inverter solar systems.

This claim is very easy to Google. Please investigate how many solar fires are caused by an AC system with microinverters. If you’re stumped about how to search for that, we recommend Googling the following phrase: “microinverter arc fire.” Go check it out. We’ll be here when you come back.

The results speak volumes.

AC solar systems reduce the risk of arc fires because they have a different electrical architecture. The technology is different. This isn’t one brand competing against another. This is not Enphase versus Whoever, this is about safety in two different types of technology.

The following video makes a pretty good argument for the importance of rapid shutdown in a solar system. An Amazon building caught fire and firefighters couldn’t shut down the high-voltage DC system.

The fire grew because they couldn’t switch off the power from the solar panels. This shows the need for safer systems. Microinverters would have made a big difference. They have a feature called “rapid shutdown,” making firefighting safer.

High-voltage DC systems are risky during fires because they can’t be easily shut down.

AC systems with microinverters can be fully shut down with the flip of a switch.

Saving money with string inverters can be dangerous. Firefighters can’t work safely with high-voltage DC systems, so they let the Amazon fire burn. There’s a spectacularly good chance they will do the same if you invest in a high-voltage DC system for your home.

The video also mentioned (repeatedly) how crucial it is to get a competent solar installer. It’s about safety, not just cost. We need to focus on preventing fires and protecting people.

It’s in your best interest to know how different solar systems work before you invest in one. Educating everyone about these differences is important. It helps prevent fires and protect lives and property.

If you’re interested in learning more about the rapid shutdown feature in solar systems, you might want to check out the following article titled, How Important is Rapid Shutdown in a High Voltage DC Solar System?

Find out more

MC4 Solar Connectors

MC4 connectors are single-contact, weatherproof connectors. They snap together with a locking mechanism, which ensures a secure and stable connection. They are designed for use with solar panels and other solar equipment. The “MC” stands for “multi-contact,” and the “4” refers to the 4 mm contact pin.

Two black electrical connectors, one male and one female, with a cylindrical shape and ridged exterior, shown on a solid black background.

MC4 connectors are essential components in solar installations because they ensure safe, reliable, and efficient connections between solar panels and other system components.

MC4 connectors are found across almost every solar system. Enphase has MC4 connectors, string inverters have MC4 connectors, SolarEdge systems have MC4 connectors.

In an Enphase system, there are zero man-made MC4 crimps on the roof. A man-made MC4 crimp refers to the manual process of attaching an MC4 connector to a cable in on-site.

This is the meat of the issue: eliminating human error. What fails in solar installations is the installer’s hand crimping a cable to an MC4 connector.

Microinverters already have the MC4 in it, and panels have MC4 plugs on them, the MC4 crimp on a panel is already done by a machine at a factory, not a human. The machine will manufacture it perfectly every time. There’s no human error. So, all our guys need to do on site is plug the panel into the microinverter.

MC4 connectors eliminate one more possibility of human error in solar installations.

Here are a few more reasons why MC4 connectors are important in a solar system installation:

Ease of Installation:

MC4 connectors are easy to install and connect. They have a plug-and-play design, which speeds up the installation process and reduces labour costs. The wires are crimped in a factory and assembled off-site.

It’s the plug-and-play design that makes them so wonderfully safe in solar installations. When those two ends snap together, you can hear it.

By providing a stable and secure connection, MC4 connectors keep your system safe when used correctly.


MC4 connectors are designed to handle high voltages and currents safely. They help prevent accidental disconnections and reduce the risk of electric shock.

MC4 plugs on a DC string system are factory crimped on panels. These are not the ones that fail. They were not crimped by humans.

On a string system, the panel plugs into the panel next to it and the voltage is cumulative. So, if you’ve got 50-volt panels, the first one is 50V, then the next one makes it 100V total, then 150V, then 200V, 250V, and it keeps going all the way up to 1000V.

Diagram of a String Inverter System showing multiple solar panels connected in series to a string inverter, which then connects to a home labeled "Home Sweet Home.

The real problem with human error in a string system installation lies at the end of the string. The final crimp is man-made. An installer is high up on the roof with a pair of pliers and some MC4 tools. The installer must strip the cable perfectly, twist it perfectly, do the crimp perfectly, attach the MC4 plug to the crimp perfectly, and then plug it into the cable.

All MC4 failures happen at the end of the string. Because that’s where the man-made crimp is.  

Within an Enphase system, there are 0 man-made crimps. Microinverters with a genuine Enphase trunking cable don’t need any crimps at the end of the panels.

MC4 plugs are in every single system, but the fewer of them that your preferred solar installer crimps on the roof, the better.

We don’t even stock MC4 plugs. We don’t need to do it. We install microinverters and everything is plug-and-play.


These connectors are built to withstand harsh weather conditions, including rain, snow, and high temperatures. This ensures that the solar system remains operational in various environmental conditions.


MC4 connectors are widely used in the solar industry, making them compatible with most solar panels and inverters. This standardization simplifies the design and installation of solar systems. Some installers believe that MC4 connectors are interchangeable. They are not.

Mixing connectors from different manufacturers is unsafe and illegal. They must be UL-rated for safety. Improper connections can cause arcs, leading to potential fires.

Microinverters have MC4 connections integrated into their design. There’s no need for any adapter cables.  

Can’t say the same for high voltage DC power systems.

The fewer connections you have, the less human error exists in your system. The less human error, the less chance of an arc fault. Fewer arc faults mean fewer fires.

If you’re interested in learning a bit more about how installation craftsmanship affects the efficiency of your solar system, you might want to check out the following article titled, In-house Installers vs. Subcontractors: Which is Better?

Get more info

Microinverters as a Safety Solution

By now, you’re sure to understand how biased we are on this topic. It’s why we exclusively install Enphase microinverters.

Arc faults are a major concern in solar systems. The wiring in high voltage DC systems runs from the solar panels on the roof down to the inverters. This makes them difficult to shut down in an emergency, increasing the risk of a sustained fire.

There are still 600 – 1,000 volts in the cable coming down from the roof.

Diagram of a High Voltage DC String System. Solar panels connect to a central inverter and main switchboard, with power from the grid. Instructions show where to cut or not cut power.

Unlike string inverters, which convert DC to AC at a central point, microinverters are installed under each solar panel. The high voltage DC power is converted to much safer AC power immediately.

The 600 – 1,000 volts that firefighters worry about in the cables of a string solar system are eliminated in an AC power system with microinverters.

Saving money with string inverters meets an immediate need, but the safety risks are high. Prioritizing safety over cost can prevent fires and protect both property and lives.

If you’re interested in learning more about the other advantages of microinverters, you might want to check out the following article titled, Myths & Misconceptions About Solar Microinverters.

Learn about microinverters

Parting Thoughts from Jake Warner, Managing Director of Penrith Solar Centre

A smiling man in a black polo shirt standing in front of a blurred sign that reads "the future is electric."

All high voltage DC architecture is susceptible to arc faults. It’s one of the biggest risks when installing solar because this causes fires. Microinverters eliminate any risk of an arc fault.

There are string inverter manufacturers such as Fronius and Sungrow that are integrating arc fault protection into their inverters now. They’re saying that they can detect an arc and turn the inverter off.

That’s all well and good if the arc is just localised to one of the polarities of the cable coming from the roof to the ground. If the arc was on the positive or the negative, then it would be fine.

But if that arc has already caused a fire on the roof and caused a DC short, that arc fault protection is absolutely useless. The fire (and the DC power that’s fuelling the fire) will just keep on going until the sun goes down.

So, it’s all well and good to say that arc fault detectors will eliminate some fires, and yes, that is true, it will eliminate some fires. But if a rat or a rodent or possum, which we very commonly see, chews through both conductors of your solar system, or your solar system shorts out against metal, you know, metal in your roof or like a Colourbond roof, then arc fault protection is basically useless.

It’s great that string inverters are acknowledging that there is a problem there, but the solution is not good enough.

Speak with an expert

Conclusion: Arc Fires and Solar Equipment

Arc fires in solar systems are a significant risk. High-voltage DC systems can create arc faults, leading to fires. These systems operate with high voltage, which can cause faults in wiring and connections.

Microinverters eliminate these risks. They have rapid shutdown and reduce the likelihood of arc faults.

At Penrith Solar Centre, we want you to understand the differences in solar architecture. High-voltage DC systems pose significant risks during fires. AC systems with microinverters offer better safety. Educating customers and installers about these differences is crucial. We will never reach Net Zero by 2050 if we are all this flammable.

A group of people posing in front of a building at Penrith Solar Centre.

If you’re interested in reading up on safety in solar installations, you might want to check out the following article titled, Solar Safety: Microinverters vs. String Inverters.

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