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What Are The Different Types Of Solar Panel Connectors?

Not all solar panel connectors are the same. Lets explore their differences.

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Last updated:
Reviewed by
Carlos Huerta
Guide

Solar panel connectors are crucial items in the installation of solar generation systems. The connector speeds up the installation and makes it relatively easy by ensuring continuity between cables that connect the modules in the solar array. This allows the current to flow from the solar panel to the solar charge controller, into the solar inverter, and then power every appliance at the home.

The solar connector plugged at the end of each wire is the main one responsible for simplifying modular installations for solar systems. By using these connectors, a solar installer can reconfigure the modules when increasing the size of the system, installing modules in parallel or series to achieve the desired array.

Using the right solar connector is important for the wiring of photovoltaic (PV) modules with other components in the system, especially when using a combiner box for larger systems. In this article, we will dive into the basics of solar connectors, you will learn about the different types of solar connectors, the differences among them, and many other important aspects that you should know.

What are the different types of solar connectors?

In short, the most popular solar connectors are:

  • MC3
  • MC4
  • Helios H4
  • SolarLok
  • Radox

The designs for these connectors in the last 20 years have been regularly improving, making them more secure and ensuring the proper wiring for the solar array. Lets explore each connector type in more detail.

MC3

The MC3 connector was the most popular solar panel connector in past years, being a really good and simple option manufactured by Multi-Contact. This connector has a 3 mm single-contact cylindrical plug for the male connectors and a socket shell design for the female connectors.

This connector has the female and male lead respectively working as the positive and negative lead, but they are mainly a reference for a solar installer to know where the cable is coming from and where it should go. MC3 connectors have been outdated by the better and more improved version: The MC4 connector.

MC4

The MC4 connector was designed by Multi-Contact as well. The connector features a single-contact cylindrical plug perfectly fitting the socket shell working as the female connector. The MC4 also has a safety class II system, UV protection, an impedance below 0.5 Ω, and an IP68 Ingress Protection (IP) index.

By being such a simple yet secure connector, the MC4 makes solar installations very easy. This type of connector is perfect for crimping solar wires with any type of length in small, medium, or even large installations that might have a combiner box and a high-capacity battery bank.

Helios H4

The Helios H4 is another popular type of solar panel connector that is manufactured by Amphenol. This connector has a design compatible with the MC4, making it easier for homeowners to install one or the other without worrying about compatibility.

SolarLok

The SolarLok is also known as the Tyco connector for wires, which was a very popular connector around the year 2000. This connector is manufactured by Tyco and can still be seen in old installations. The Tyco SolarLok connector for solar cables was used for connecting one module to the next one in a series or parallel installation, depending on the required configuration for the solar array.

Radox

The Radox connectors are a quality option manufactured by Huber + Suhner that features a 15-year warranty. These connectors use copper-beryllium contacts made with a lamella design to properly ensure the right passage of current through the wires. Although, these connectors were manufactured in Europe and did not meet the US market requirements, which is why they are not commonly used in many installations nowadays.

Are solar panel connectors universal?

In the past, PV modules used MC3, SolarLok, or another type of connector. With all these options available, homeowners generally had a rough time when they were going to purchase panels since they could get confused with the connector or had to cut the installed connector in the end and crimp their own at the cable with a crimping tool.

The connectivity issue was a clear sign that the solar industry had to do something about it to achieve the standardization of a solar connector for PV modules. This is why the MC4 connector was established in the end as the standard for connecting PV modules and other solar equipment, especially since they were more secure and had a quality design.

The MC4 excellent performance and high-security level have not been paralleled by any other collector. Due to the popularity of the MC4 connectors, it is now considered that solar panel connectors are universal since practically all manufacturers use the MC4 connector.  

What is the difference between MC3 and MC4 connectors?

MC3 is the wire connector that Multi-Contact designed before the MC4, meaning that the MC4 is the better and improved version.

The first difference between both connectors is the ingress protection (IP) rating. The MC3 has an IP65 index that fully protects the cable against dust, but only ensures the wire protection against low-pressure water sources. The MC4 on the other hand protects the wire against dust particles and fully submersion in water for short periods, making it much safer in unfavorable weather.

The second and most important difference is the locking system. The MC3 connector does not protect wire disconnections, allowing the cable to be easily disconnected which can cause an electric arc in the cable if the module is generating energy, which is a very dangerous phenomenon. The MC4 features a positive locking system which can only be separated using an MC4 assembly/disassembly tool.

The MC4 connector ends up being a much safer option, making it ideal for solar cables with practically any length at solar generation systems. If you want to get rid of your old MC3 connectors and place some MC4 connectors for each PV module at your home, you just need to cut the MC3 connector at the cables end and add the MC4 connector by crimping it to the wire with a crimping tool.

How to connect solar connector wires

Properly connecting or wiring a solar installation for several PV modules can be done when using the right components and if you know the basics about it. The first thing you need to learn is that for common connectors like the MC4, the female connector is the positive lead and the male is the negative one.

Installing PV modules in series will increase the output voltage while keeping the power output the same. To install a string of panels in series, you need to plug the positive lead of each panel to the negative of the next one. To close the circuit in the end you just have to connect the remaining positive and negative leads into the inverter or solar charge controller, depending on your system.

Series Connection of Solar Panels. Source: Solar-Electric

When the solar panels are plugged in parallel, they will increase the electrical current while maintaining the output voltage. For parallel installations, you have to connect positive leads between each other, the same applies for the negative ones. In order to do this you have to use an MC4 branch connector that allows you to connect several leads together.  You can install two branches with a 2-way MC4 branch connector, three branches with a 3-way MC4 branch connector, and so on.

Parallel Connection of Solar Panels. Source: Solarmo

The series-parallel connection combines both series and parallel installations for solar panels, this configuration increases both the voltage and electrical current output. In this case, you need to install equal strings of panels in series and then install them in parallel with the other branches.

Series/Parallel Connection of Solar Panels. Source: Renogy

Conclusion

While you can shop for any type of solar connector when installing solar panels, it is important to take into account safety locking mechanisms, IP index, and impedance of the connector. The MC4 connector features outstanding specifications in these categories and more, making it the best option for any solar installation, even in combined or hybrid installations when you power a home with solar panels and wind turbines.

With rated parameters of 600V and 22 – 30 amps for an MC4 connector with a size of 2.5 – 4.0 mm², you can rest assured that this is the right connector for your PV modules. MC4 connectors are perfect for every situation since they can be used both in small solar installations with direct connections and in solar farms with long-distance cables and a combiner box.

FAQs

Learning about solar connectors is important to avoid mistakes and know how to properly fix any type of situation. Here we will answer the most Frequently Asked Questions about solar connectors.


What size wire can you use for each solar panel connector?


Each type of solar connector has specific max-rated amps that you can send through it, which is related to the capacity of the solar panels, inverter, solar charge controller, and of course the wire. You can search for the recommended wire gauge for each connector in the manufacturer datasheet, but this is not regularly an issue for residential solar installations.

The MC4 connector withstands up to 22 amps for the 2.5 mm² option and 30 amps for the 4.0 – 6.0 mm² connector. Depending on the installation requirements, you might want to search for 14 AWG, 10 AWG, or up to 8 AWG cables for these solar connectors.

How do you crimp a solar connector?


To ensure proper power transfer from the PV modules to the rest of the installation, it is important to properly crimp every connector. Crimping a connector means securing the wire into the connector that will be used in the solar system.

Crimping or assembling a solar connector is relatively easy with the right tool. To crimp an MC4 connector you should expose about ½ inch of the cable, insert the connector pin into the respective wire gauge cavity in the tool, and gently hold it in place. Then insert the cable by the opposite end of the pin and finally press the crimping tool to properly crimp the MC4 solar connector to the solar cable.

If you have a solar panel or a string series of PV modules that seem to be producing less electricity than the rest, it could be a sign that there is a wrongly crimped connector. To solve this situation, you can re-crimp the solar connector or test the individual performance for each panel in the string before you connect each panel back.

Are solar panel connectors waterproof?


Solar panel connectors are protected concerning an IP index. The first number of the index represents the protection against solid objects while the second number represents the protection against liquids. In this case, the number that you should consider is the second one.

The MC4 connector has an IP67 protection index. This number means that the connector is protected against submersion in up to 3 ft. of water for up to 30 minutes, any type of pressurized source of water is of course included within this protection index. Knowing this level of protection, you can consider your MC4 solar connector to be waterproof as long as it is only submerged in water for 30 minutes or less.

Which lead is positive and which negative?

The female connector is the positive lead and the male is the negative one.

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Author Bio

Carlos Huerta

Electrical Engineer with background in solar PV designs for residential and commercial projects as well as power systems development. Fan of renewable energy topics and projects. Technical writer for papers, articles and research in related topics to sustainability and especially solar power.

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