Updated on October 14, 2025
Most homeowners shopping for solar are unaware of the risks associated with arc faults. The phrase 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 it 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 seems to be a threat to solar systems nationwide.
What is an arc fault?
At PSC Energy, 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 and installer).
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
- FAQ: Arc Faults
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, each with a different kind of electrical architecture.
DC Architecture: String inverter solar systems send direct current (DC) power to an inverter on the side of the house to convert it to AC power.
AC Architecture: In an Enphase microinverter system, the DC power is converted to AC power at the panel before being sent to the house. This is a system with AC architecture.
The arc faults that happen in a system with DC power are typically more dangerous. Higher voltage leads to bigger arcs (which are kind of like sparks), which can more easily catch fire. Lower-voltage AC power systems don’t have this issue because they can automatically shut off when an arc is detected.
Even a minor equipment malfunction, like a frayed cable or a loose electrical connection, can trigger a arc fault, potentially causing a fire.
Arc faults can reach temperatures of up to 1,085°C. They can easily melt materials like glass, copper, and aluminium. This is why a sound solar installation is critical.
If you’re interested in learning a bit more about solar panels and energy systems, you might want to check out the following article titled, Are Solar Panels Worth It in NSW, Australia? A Price Breakdown for 2025.
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.
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. Microinverters, string inverters, and SolarEdge systems all have MC4 connectors.
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 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.
MC4 connectors eliminate one more possibility of human error in solar installations.
Here are a few more reasons why MC4 connectors are essential 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.
Safety:
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. Humans did not crimp them.
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.
You don’t want an installer high up on the roof with a pair of pliers and some MC4 tools.
MC4 plugs are in every single system, but the fewer of them that your preferred solar installer crimps on the roof, the better.
Reliability:
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.
Compatibility:
MC4 connectors are widely used in the solar industry, making them compatible with most solar panels and inverters. This standardisation 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, as improper connections can cause arcs, which may lead to potential fires.
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?
Conclusion: Arc Fires and Solar Equipment
Arc fires in solar systems are a significant risk. DC systems can experience arc faults more easily, leading to fires without a sound solar installation. AC systems are less risky.
The greatest protection for your solar system and home is a high quality installation that’s safe and secure.
At PSC Energy, we want you to understand the differences in solar architecture. We install both DC systems and AC systems. While there’s always a risk of fire with electricity, our installations go the extra mile. It’s what we do.
If you’re interested in learning a bit more about weighing the cost of solar against the cost of the grid, you might want to check out the following article titled, Cost of Solar Panels vs. Cost of Energy from the Grid.
FAQ: Arc Faults
What is an arc fault in a solar system?
An arc fault is a sudden electrical discharge between conductors across a gap. It creates intense heat that can damage insulation and start a fire. Loose terminations, poor crimps, gaps, or moisture often cause arc faults.
Why are DC arc faults more dangerous than AC arcs?
High-voltage DC on string systems produces hot, sustained arcs that can keep burning. AC arcs are brief and self-extinguish when the current crosses zero each cycle. That makes AC architecture safer on a roof.
How hot can a DC arc get?
DC arc faults can reach temperatures around 1,085°C. That is hot enough to melt copper, aluminium, and even glass.
Where does high-voltage DC live in a string inverter system?
Panels connect in series on the roof. Voltage stacks panel by panel and can climb into the 600–1,000 volt range before it travels down to the inverter.
How do microinverters reduce arc fault risk?
Microinverters convert DC to AC at each panel. That removes long runs of high-voltage DC across the roof. The trunk is AC, which reduces the chance of a sustained arc and adds rapid shutdown capability.
What is rapid shutdown, and why does it matter?
Rapid shutdown is a safety feature that de-energises rooftop circuits quickly. It protects firefighters and homeowners during an emergency by dropping voltage at the array level.
Can arc fault detection in string inverters solve the problem?
Arc fault detection can help, but it is not a cure-all. If a short or fire has already started on the roof, detection at the inverter may not stop the event. Damaged conductors and live DC can keep feeding a fire until the sun sets.
What are MC4 connectors, and why are they important?
MC4s are weatherproof, locking connectors used to join solar cables and equipment. Factory-crimped MC4s on panels and microinverters give reliable, repeatable terminations that lower arc risk.
Are MC4 connectors interchangeable between brands?
No. Mixing MC4-style connectors from different makers is unsafe and non-compliant. Use matched, listed pairs from the same manufacturer to avoid poor mating and arcing.
Where do most MC4 failures occur on string systems?
Failures often happen at the end of the string, where installers make a hand crimp on the roof. Any error in strip length, crimp pressure, or assembly can create a hot spot and an arc.
How do microinverters change MC4 risk on the roof?
Microinverters and panels arrive with factory MC4 leads. Installers plug them together. Fewer field crimps means fewer human-error failure points and lower arc risk.
What causes arc faults besides bad crimps?
Common causes include loose connectors, damaged insulation, crossed conductors, trapped or pinched cables, water ingress, UV-degraded plastics, and animal damage from rodents or birds.
How do arc faults relate to firefighter safety?
High-voltage DC is hard to de-energise at the roof during a fire. That can delay suppression. AC architecture with rapid shutdown lowers rooftop voltage and makes the scene safer.
Can weather trigger arc faults?
Yes. Heat, UV, and thermal cycling age plastics and seals. Wind can rub cables against sharp edges. Moisture can intrude into compromised connectors. Good hardware and tidy routing help prevent this.
How can I spot early warning signs of an arc risk?
Watch for inverter or app alerts, tripped protection, burnt smells, discoloured connectors, or unexplained production drops. Do not open rooftop connectors. Call your installer for inspection.
Do microinverters eliminate arc faults?
No system is risk-free, but microinverters remove long high-voltage DC runs and rely on factory terminations. That design dramatically reduces the chance and impact of arcing on the roof.
What maintenance helps prevent arc faults?
Keep the area around the array clear of debris. Schedule checks after major storms. Review monitoring data regularly. Book a professional inspection if you notice faults, alerts, or production changes.
Are AC systems always the safest choice?
For rooftop safety, AC architecture has substantial advantages. It reduces high-voltage DC exposure and supports rapid shutdown. Your site, budget, and goals still matter, so weigh the whole design.
What should I do if I suspect an arc or smell burning near the array?
If it is safe, isolate the solar system using the marked switches and call your installer. If you see smoke or fire, evacuate and call emergency services. Do not touch rooftop connectors or cables.
Can animals really cause arc faults?
Yes. Rodents and possums can chew through insulation and expose conductors. Use protected cable routes, screened entry points, and tidy wiring to reduce that risk.
How do I verify that rapid shutdown works on my system?
Ask the installer to demonstrate the shutdown procedure and show where the switches are. Confirm that the labels, user instructions, and the monitoring app reflect the state change.
