What is a relay and why is it important for solar inverters?


A solar inverter is a crucial component of a solar photovoltaic (PV) system – more commonly known to your everyday user as a solar panel system. Solar inverters are responsible for the task of changing the direct current (DC) into alternating current (AC) through solar energy.

This conversion is necessary for the day-to-day use of solar energy due to the cost and high risk of fires associated with DC energy. Some examples of appliances that require AC power include many household items such as light fittings, washing machines, televisions, and air-conditioning units.

Since solar inverters are responsible for converting raw energy into usable electricity, specific safety components must be included to ensure the inverter functions without causing serious incidents. For example, if a solar inverter isn’t properly installed, it can sometimes overheat or experience an isolation fault. And because the wiring leading to the inverter is producing potentially lethal amounts of DC electricity, any faults or irregularities can become dangerous very quickly.

Plus, installing and using an inverter the right way can help significantly prolong both its lifecycle and efficiency.


Relays in solar inverters

One of the key components that can help improve the safety and effectiveness of a solar inverter is a simple electromechanical switch, known as a relay.

Similarly to how we would manually use normal switches to close or open a circuit, a relay also connects or disconnects two circuits. However, relays are electrically operated switches that are placed at the output side of an inverter. So, unlike our manually operated switches, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit.

The way relays and inverters work together is pretty intuitive: If one malfunctions, the other is ready to step in and ensure that everything stays safe. For instance, if solar inverters (for whatever reason) aren’t working or experience a breakdown in functionality, relays will cut the inverters off from the main grid to ensure the safety of both the users and the equipment. In turn, when relays go wrong or lose performance, inverters will disconnect from the grid or reduce the output power.

In a normal circuit, power flows until the relay is activated. Once the relay is activated, it disconnects the circuit and power stops flowing. The power then only returns to the circuit when the relay is deactivated again. The same can be said for inverters: Relays are only activated when something goes wrong or if the inverter stops working. The only difference is that this process happens automatically.

The status of relays is automatically controlled by the inverter itself. If there is no relay inside the inverter, then there must be an external relay to ensure safety.


Standards and regulations

Even if the solar PV system inverter has a preinstalled isolation switch, the electrical wiring connected to the inverter still carries live and potentially lethal amounts of DC electricity. Fires have been known to occur within inverters that fail to properly manage the current flowing through them. And despite sensors and other safety features being present, fires caused by inverters in a solar PV system can still happen.

Relays can significantly reduce the risk of hazards occurring within an inverter. Because of this, many countries have made relays compulsory for inverters within their PV standards and regulations.

Europe’s IEC 62109-1 standard now states that components such as motors, relays, other electromagnetic devices, and heaters, which are normally operated only intermittently, shall be operated continuously.

Similarly, Brazil’s INMETRO ORDINANCE 140_2022 also states that the use of relays and other safety features has become a mandatory consideration for the installation of solar inverters.


Safety is our priority 

It’s rare for something as dangerous as a fire to actually happen in real life, thanks to advances in solar technology, the breadth of expertise within the field, and the know-how of installation professionals.

However, this also means that some manufacturers don’t give enough attention to relays, and tend not to place them within their products. And it’s fair to assume that general users either don’t know about relays, or wouldn’t know how to disassemble an inverter to check for one. Even if users do know how to disassemble it, doing so would invalidate the manufacturer’s warranty and may result in accidental damage to the internal structure. So in most cases, people who have PV systems installed may not be aware that important safety equipment could be missing.

Hoymiles is all about ensuring the safety and efficiency of PV systems for years to come. Our microinverters come with the lowest failure rates and the very best safety components as standard.

Our industry-leading microinverters are strictly compliant with local electrical standards and ensure your safety. Hoymiles’ installer-trusted technology is built to last, by a team who are committed to expertly delivering innovation through our products.

When you choose Hoymiles, you’re choosing the ultimate safety.