The Cost $$ of Not Learning About Solar Connectors: Series

Here we are, our first article, how exciting! And what would be a better topic for it than solar connectors.

Why Solar Connectors?

Solar connectors are on the top of the list of root cause components that tend to cause the most severe impact when serious issues arise in solar systems, namely fires. According to a study by TüV Rheinland, connectors, and connector-related issues, represent the single greatest risk to a PV system's performance and safety.

However, connectors don’t usually get the attention they deserve. They are a key component of a solar PV system and hold an important function: to provide a low-resistance connection between solar modules and other components while maintaining their integrity under extreme weather conditions for more than 25 years.

Crazy, right? A metal piece covered with “plastic” that is exposed to the elements for more than 25 years, think about it.

Over the next few weeks, we are going to publish a series of posts about connectors, from their history, curiosities, myths, lessons learned over the years, how to inspect them, and more. Ready for the ride?

So, let's start with the definition and a little bit of their history.

What is a solar connector?

A solar connector is a type of DC electromechanical device used to join electrical conductors and create an electrical circuit. They typically have two removable parts, the Male or Plug, and the Female or Socket.

Curiosity: We have seen a lot of people confusing which part is the Male and the Female. The reason is that the plastic body is shaped in reverse, however, the metal pin is what drives the gender nomenclature. So, keep this in mind.

Understanding modern connectors requires looking back in time.

The National Electric Code, NEC, requires that any connection above 50 V must be made by a licensed electrician. This was an issue, so a few companies around the year 2000 came up with a solution to address this requirement. They created a push-fit connector that met the definition of a convenience receptacle, meaning they could be (legally) connected by anyone. Two players became the most common connectors during this period, the Radox connector and MC3 connector by Multi-Contact, both looked like weather-sealed phono jacks.

In 2008, the NEC came up with a new requirement to prevent people from opening connectors under load. Now, connectors must have “positive locking” mechanisms, meaning that they could be plugged in by hand but unplugged by a special tool.

MYTH: The un-locking tool can be used to torque the end cap of connectors. When it slips means that it is at the right torque. This is COMPLETELY FALSE. These tools are designed to help during connector assembly to get the first torque, however, a certified tool (yes, because the tool used to make the connector also needs to be certified as part of the assembly) should be used to properly torque connectors.

Continuing with the story, Radox, one of the main players at that time, did not come up with a new connector version to address the new requirement and effectively dropped out of the connector story. Multi-Contact USA and Tyco Electronics, also a US company, came up with a new connector that complied with the new requirements.

Tyco’s connector was more annoying to disconnect in the field and Multi-Contact slowly gained more popularity to become the market leader.

MC4 became the “industry standard” or “most common” solar connector. The MC4 stands for Multi-Contact (now St?ubli Electrical Connectors) and the 4 for the 4 mm diameter contact pin.

Below is an exploded view of MC4 connector (a fake one, yes the one on the Wikipedia page is not a legit St?ubli connector) :

In 2008, Amphenol came up with a connector that has the same MC4 shape (the industry at the time called it “MC4 Compatible”) the Helios H4. Since 2008, there is a long list of MC4 compatible connectors out there. 

One of the latest code updates about this topic is Section 690.33(C) of the NEC 2020 that says, “Where mating connectors are not of the identical type and brand, they shall be listed and identified for intermatability, as described in the manufacturer’s instructions.” And the term intermatability is used in UL 6703, “Connectors for Use in Photovoltaic Systems”. This reinforces the fact of non-compatibility unless it has been tested together.

Here are some other connector samples to know about:

Connectors' key features:

• Interlockable
• Water and dust resistant, typically IP67 or 68 (max IP)
• UV resistant
• Double-insulated
• Able to handle up to 1500 Vdc
• Able to handle up to 30 A
• Temperature range -40°C to +90°C

This is all for now. If you enjoyed this article and thought it was informational or you learned something new, please let us know in the comments below. In the next post, we will be talking about the most common issues we have come across and ways of inspecting connectors in the field. Follow us if you don't want to miss it.

Our software SolarGrade is a solar & storage inspection software designed to help solar professionals to be more efficient, effective, and consistent to provide cost-effective, high-quality asset care.

Our goal is to ensure that solar and storage assets fulfill their promise as responsible and reliable energy sources beyond our generation. More info: www.SolarGrade.io

?References and Credits

• All photos are from the manufacturers' websites, so thanks to Tyco Electronics, Amphenol, Staubli, Radox, Tonglin Electric, Phoenix Contact
• https://en.wikipedia.org/wiki/MC4_connector?