The Complete Guide for Solar Panel Connectors

Solar panel connectors are one of the most underestimated components in photovoltaic (PV) installations, but they are one of the most essential. Solar connector technology improvements have granted solar installers the ability to easily and rapidly install solar arrays that will last for decades. All connections remain secure unless they are disconnected intentionally for maintenance or other reasons.

If you want to learn more about solar panel connectors, you will find all the information you require in this article. Here you will learn the basics about connectors for solar panels, how to connect the different types of solar panel connectors, what their main specifications are, and which one is the best for you.

Solar Panel Connector by Multi-Contact
Image: Multi-Contact

Starting with the basics

Before diving into the world of solar panel connectors, you should learn the basics about them. In this section, we explain what they are, their evolution throughout history, and more.

What is a solar panel connector?

Solar panels come with wires connected on one end to the junction box while on the other to a solar panel connector. The solar panel connector is used to interconnect solar panels in PV installations. Their main task is ensuring power continuity and electricity flow throughout the whole solar array. There are many types of solar connectors in the market, but the most popular option available is the MC4 connector.

A brief history of the most important solar panel connectors

PV technology was first invented in 1883, but the technology did not become popular until 1950 when it captured the eye of Bell Laboratories. With the increasing number of applications for PV technology, there was a need for a safe and easy-to-use solar panel connector, this is when MC3 solar connectors were created.

The MC3 solar connector was invented in 1996, named after Multi-Contact (MC), the company that invented it, and the 3mm2 size of the contact pin installed within. The MC4 solar connector created in 2004 is an improved version of the MC3 connector, featuring a 4mm2 contact pin, an efficient safety mechanism, and a practical installation that turned it into a standard in the solar industry.

Why are solar panel connectors so important for solar PV systems?

Solar panel connectors safely lock PV wires in place while resisting harsh exposure to the elements and solar radiation for decades. This safety mechanism also reduces electrical arcing, making solar arrays safer.

Another important task of solar panel connectors is reducing the electrical resistance between PV modules by properly connecting wires. This reduces electrical hot spots (not the same as solar hot spots) that could otherwise overheat wires or connectors as a result of loose connections or other factors. This also makes PV installations much safer by reducing possible fire hazards.  

How are solar panel connectors selected?

MC4 connectors have become the standard in the solar industry, but there are a few other solar connectors that are still used by some installers. Some of these include Amphenol, Tyco, Radox, and the outdated MC3 solar connector.

To select the right solar panel connector for each application, installers consider different features and technical specifications. The following list illustrates some of the most important factors considered when selecting a solar connector:

  • Max. voltage
  • Max. current
  • Max. temperature
  • Contact resistance
  • Contact material
  • Ingress Protection (IP) index
  • Safety class.
  • Wire cross-section (wire size).

Solar panel connections: How are solar panel connectors used?

Learning how to use solar panel connectors is extremely important if you own a PV system. In this section, we teach you how to attach a solar connector to a wire, lock or unlock it, and install it in series, parallel, and series-parallel.

Crimping & tightening of solar panel connectors

Solar panels do not always come with the solar connector attached. Attaching a solar panel connector to a PV wire is a two-step process: (1) crimping and (2) tightening the connector, to do this you require a wire stripper, crimping tool, and a solar panel connector assembly tool.

  • First, you strip the wire, then place the metal connector on top, and finally, use the crimping tool to crimp the metal connector to the wire.
  • After the metal conductor is crimped to the wire, you have to place the metal connector into the terminal cover, strain reliever, and compression sleeve.
  • Finally, you plug the metal connector into the connector housing and screw all the components together using the assembly tool. Properly tightening MC4 solar connectors ensures they are water-tight and safe to use.

Locking and unlocking solar panel connectors

The connectors for solar panels feature a locking and unlocking mechanism that keeps them tucked into place, reducing the risks of electrical hot spots and arcing. This mechanism also makes it easy for solar installers to connect the whole solar array.

Locking an MC4, Amphenol, Tyco, Tonglin, and Hosiden solar connector just requires connecting the male and female connectors until safety pins are plugged into place. All connectors should be unlocked with the assembly tool, but the MC4, Tonglin, and Hosiden connectors can be unlocked by pushing the safety pins as you pull the connectors.

Radox solar connectors are locked and unlocked by a screwing mechanism. You plug the male and female solar connectors until there is a 2 mm breach between them, then you screw them together. To disconnect them, you perform the opposite process.

Installation of series, parallel, and series-parallel solar arrays using solar connectors

Solar connectors can be used to connect solar panels in series, parallel, or series-parallel. Installing them in series is quite simple while installing them in parallel requires an additional component.

To connect solar panels in series you just plug the positive connector of a PV module into the negative connector of the next module. At the end of the string, you plug the negative connector of the first module with the positive connector of the last one to the inverter.

Solar Panels Connected in Parallel With 4-In-1 MC4 Combiners
Image: Renogy

To connect solar panels in parallel, you require an additional component known as an MC4 combiner (or MC4 multi-branch connector), this name differs for other types of solar panel connectors. The image above illustrates a 4-in-1 MC4 combiner, but these components can be 2 in 1, 3 in 1, and so on. By using a 4-in-1 MC4 combiner you can connect up to 4 solar panels (or strings of panels) in parallel. This is done by connecting all the positive leads from the 4 PV modules to a single MC4 combiner. Then, the negative leads of the 4 panels are connected together through another MC4 combiner. This results in just two wires carrying all the current from the solar panels that can be easily connected to an inverter.

For the series-parallel connection, you apply what you just learned to connect two or more strings of solar panels in series into a parallel connection.

What are the most important types of solar connectors used in the solar industry?

MC4

The MC4 solar connectors have become the standard connector in the solar industry. This connector invented by Multi-Contact/Stäubli, complies with the strict regulations of the National Electrical Code (NEC), it also features a safety lock mechanism that makes it ideal for most installations.

Amphenol

Amphenol is a solar connector manufacturer that has released multiple solutions for PV installations, featuring a similar design to the MC4 connector, except that this connector requires the assembly tool to be unlocked.

Tyco

Tyco Electronics also designs all types of solar connectors under the SOLARLOK line of products. The SOLARLOK PV4 connector is UL and TÜV certified, complying with NEC regulations.

MC3

The MC3 solar connector is usually considered an outdated solar connector, but it is still used in some PV applications. This connector features similar specifications to the MC4, but without any safety mechanism.

Radox

The Radox twist lock solar connector designed by Huber + Suhner is UL and TÜV certified, features a housing and contact element made of high-quality beryllium copper to conduct electricity, a high mechanical resistance, UV and ozone resistance, and an easy assembly system.

Comparing the different types of solar panel connectors

The best way to get a better understanding of options available is through a table. In this section, we compare each of the most popular solar connectors by listing their technical specs as well.

 MC4AmphenolTycoMC3Radox
Cable Cross-Section (mm2)2.5 - 102.5 - 64 - 62.5 - 104 - 6
Contact MaterialTin-platted copperTin-platted copperTin-platted copperTin-platted copperTin-platted brass
Rated Current39 - 104A15 - 45A20 - 30A20 - 43A38A
Max. Voltage1,000V1,500V1,500V1,000V1,000V
IP IndexIP65IP68IP65IP68IP68
Max. Temperature105ºC120ºC-105ºC85ºC
Safety ClassIIIIIIIIII
Safety MechanismPlug lockPlug lockPlug lockNoneTwist lock
Locking/Unlocking ToolUseful but not requiredRequiredRequiredNot requiredNot required

Most solar connectors feature similar technical specifications in general, but the small variations are what make them unique. The MC4 could be considered the best option overall since it can conduct a higher current and is more practical to use.

The MC4 connector originally manufactured by Multi-Contact has become the industry standard for a multitude of reasons. This connector features high-quality materials and the MULTILAM technology that increases tension between female/male connectors to reduce moisture within the connector, improving performance. These and other reasons are why using an MC4 original might be the best choice for you.

Final word: The importance of selecting the right solar panel connector

Selecting the right solar panel connector will ensure your PV system works seamlessly for decades. You might perform maintenance every few years, but you will most likely never change the solar panel connector if you use the right one.

For residential installations featuring a 600V, most solar panel connectors will do the work and function for the duration of the installation, however, we strongly recommend MC4 connectors. The MC4 connector has been tested in all types of environments, is designed to withstand the direst conditions, and is constantly being improved, the latest version released by Stäubli is the MC4-Evo 2.

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