Solar Wire Connectors: Everything you should know about them

Do you know how solar panels are connected with DC cables to carry power to the solar inverters? It is done by installing solar wire connectors! Let us understand how they work!

Solar panel modules are connected in series or parallel strings through the solar wire connectors. Additionally, they can connect modules to the inverters or power optimizers.

MC4 connectors, which have considerably replaced the MC3 and T4 connectors, are the only options that are used nowadays. 

The early 21st century (in the 2000s) witnessed solar connectors that directly connected with the wires and were exposed to corrosion and mechanical stress.

This problem made them unsustainable and, thus, unfit for use. Also, their handling required trained technicians, as directed by the National Electrical Code. This led to the launch of MC3 and T4 connectors, but the problem of unlocking under load persisted.

Considering these problems, the National Electrical Code necessitated the use of connectors that can be easily installed but won’t unlock automatically under heavy load. 

The result was the launch of ‘positive locking’ connectors, which required a manual unlock mechanism to open. MC4 solar connectors fulfil this purpose. Hence, they’ve completely taken over all other solar connectors that were launched before them.

Before understanding the features of MC4 connectors, let us first understand how MC3 and T4 solar connectors became obsolete.

Why did T4 solar wire connectors become obsolete?

Tyco International introduced T4 connectors to comply with the locking mechanism updated by the National Electrical code. The modified design of T4 connectors varied from available solar wire connectors, leading to incompatibility and limited use.

The lack of positive and negative terminals among the plug and socket design of T4 connectors also restricted their broad applicability. The reason was an inability to plug in an extension cable. 

Utilising these connectors required extra work, which could be easily avoided with the usage of other solar wire connectors with updated features.

How Could The MC3 Solar Wire Connectors not Serve The Required Purpose either?

MC3 connectors were designed to conquer the problem of the inability to be handled in the absence of a technician. However, these connectors posed another problem. They could be easily opened on a stretch or heavy load. This would further cause damage to the solar panels.

MC3 solar wire connectors were able to utilise a maximum load of 1000 voltages and 30 amperes and offer IP65 protection. It made these connectors unsuitable for areas experiencing extreme weather conditions, including regions experiencing floods. 

The severity of problems caused by installing MC3 solar connectors led to their withdrawal from usage by the National Electric Code.

So, which solar wire connector solved these problems posed by MC3 and T4? Let’s find out! 

MC4 Solar Wire Connectors 

MC4 connector is a multi-contact (MC) product. The usage of the number ‘4’ in its name signifies 4 mm2 pins. Being launched after MC3, these connectors also hold ingress protection ability rated at IP67. MC4 connectors hold an advantage in terms of durability and inability to become brittle. 

These connectors reflect resistance against factors such as UV rays, water, corrosion, and dust. Additionally, the original connectors are associated with quality material helping in good transmissibility.

One of the most vital features of MC4 connectors is that they can also resist moisture while submerged in water at 3 feet for 30 minutes.

Now, let’s move towards understanding the features and accessories used for installing the MC4 connectors! 

Features And Accessories Used For Installing MC4 Solar Wire Connectors

MC4 connectors fit perfectly, connecting the solar panels irrespective of their sizes. Small solar panels produce low currents, while large solar panels produce high power. 

Yet, both types produce resultant voltage within the handling capacity of MC4 solar wire connectors.

These connectors have interchangeable rubber water seals, screw on the end cap, and seal retainer. The non-interchangeable or specific parts include the main housing and metal crimp. An additional part, safety lock clips, is available for protection from disconnection.

The important tools required while handling MC4 connectors include a hinged, swing-out contact holder crimp tool, and combo tools comprising a disconnect and spanner wrench. 

Note that the wires should be certified by the National Electric Code and Underwriter’s Laboratory.

Connecting MC4 connectors with the power system 

MC4 solar wire connectors can be used for both series and parallel connections of solar panel modules. The series connection can be directly done via connecting positive and negative terminals. 

However, the parallel connection requires MC4 multi-branch connectors. These are further categorised into two male and two female connectors. A combiner box can be used in the situation of multiple modules (more than two).

The resultant male and female outputs will need to be connected with power. For long distances, when solar panels are installed in cabins or homes, extension cable becomes a requirement. 

The extension cable itself contains male and female connector, which is joined with female and male connectors from solar panels, respectively. Accordingly, the wire is cut per the proximity of each terminal with the power. Cut wires are further joined with the power source.


Gone are the days of using MC3 and T4 connectors! 

MC4 solar wire connectors are the only options used now. Resistance to damage and ease of handling makes them better than anything else that was launched before their release. 

Even companies pre-install the MC4 type connectors for ease of connection. You can choose MC4 connectors without an ounce of a doubt! 


Q. What is the purpose of solar wire connectors?

Solar wire connectors serve the purpose of connecting modules or photovoltaic cells, or solar cells with power systems or power optimisers such as micro inverters. 

Q. Does the market provide only original solar wire connectors?

There are both original and non-original solar wire connectors available in the market. MC4 connectors manufactured by Stäubli hold proprietary rights. The connectors manufactured by this company are considered to be original.

Q.  Do I need additional things while connecting the solar wires connectors?

Yes, you will need two tools for this purpose. These include a hinged, swing-out contact holder crimp tool and combo tools comprising a disconnect wrench and spanner wrench. 
Also, an extension cable may be required depending on the site of the solar panel installation and the distance between the solar panel and the power system at the location.