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PV system design

Solar connector types: popularity and comparison

An average PV system employs way more than 100 connectors. If you don’t pay enough attention to these seemingly insignificant components, any of the connections can render your system inoperable. Read on to discover ways to avoid compliance, warranty and other issues.

What type of connectors are used for solar panels?

Connectors are small but vital parts of any PV system. As the name suggests, they are used to connect solar panels – to each other, to the inverter, or to the module-level devices like power optimizers. Solar panel connector types are many: MC4, T4, MC3, only to name a few.

Some manufacturers use generics, which are almost always compatible with a mainstream MC4 connector and are easy to identify. Just look for phrases like ‘MC4 compatible’ in the datasheet. Unfortunately, most of the time such a combination won’t constitute a UL rated connection. A couple of solutions to this situation will be discussed further below.
UL stands for Underwriters Laboratories which tests products and technologies for safety

Most popular solar connector type: MC4

MC4 connector is by far the most popular type. So much so that nowadays almost all solar panels and module-level devices, such as power optimizers and microinverters, come with it. These connectors are UL certified and comply with the National Electric Code.

The letters MC stand for Multi-Contact – the brand name of the manufacturer that became associated with the product. The connectors are made from UV resistant material and have an IP67 rating, meaning they are fully weatherproof.

MC4 connectors feature a locking mechanism that can only be unlocked with a special tool for more reliability. Each solar panel has two connectors: male and female. They are positioned at the ends of the junction box wires. One is positive and the other is negative. As a rule, the female connector is attached to the positive lead. However, there are exceptions, so it’s best to look for the markings or perform a voltmeter test.

From leadership to obsolescence: MC3

MC3 connectors are weatherproof due to a flexible seal that protects them from precipitation. Like MC4, they are also divided into male and female types to prevent erroneous connections.

Once very popular, now MC3 connectors are mostly obsolete. Friction and suction are the only powers that prevent them from disconnecting. After a positive locking mechanism became a National Electric Code requirement, MC4 connectors took over the market. However, the MC3 are still easy to buy. People use them for older solar panels or smaller setups that don’t require compliance.

Generic by Canadian Solar: T4 solar connector

T4 connector type is produced by Canadian Solar, or to be more precise, by its subsidiary Tlian. The connectors are very similar to MC4 and employ a positive locking mechanism. They have an IP68 rating, which means they are extremely well protected from rain and dust. They can also boast a very wide operating temperature range – from -40 to 194°F.

These Canadian Solar connectors fully comply with RoHS, REACH and NEC. To disengage the connection, a T4 unlocking tool is needed. A pair of those is usually included with a set of solar connectors, but they can also be purchased separately for as little as a couple of dollars.

Be careful when mixing connectors

If we take into account all the generic types, the number of different connectors on the market will be gigantic. They differ in appearance and manufacturers, but it is rarely important to the end user. What does matter is compliance with standards, compatibility with other types and whether these mixed connections meet all relevant requirements.

Virtually all solar panels that are sold today will have solar connectors that meet all relevant regulations. However, if you’re buying used modules, inquire about the type of connectors the panels feature. MC3 connectors, for instance, are weatherproof and look fairly reliable, but the absence of a positive locking mechanism prevents them from being NEC compliant. It means that they can’t be used for connecting solar panels in most states.

Another important topic is the combination of different connector types. Compatibility is rarely an issue, because most generics are intermatable with MC4 connectors. The problem is that many of these connections do not comply with all relevant standards. Still, some do. For example, the T4 connector made by Canadian Solar. The company released a document confirming recognition of T4 and MC4 connections. In all other cases you can either choose to stick with the same connector type throughout your system or contact the manufacturer to request a warranty addendum and replace them.

Replace a solar panel connector in 6 easy steps

  1. After carefully removing the old connector, for example, by cutting it off with a cable cutter, remove about ½ inch of isolation from the tip of the cable. 
  2. A typical connector has 4 main elements. Unscrew the cap to disassemble it.
  3. Then put the wire through the cap. Do the same with the cable gland.
  4. Next goes the pin: secure it in the appropriate slot of the crimping tool, then feed the exposed end of the cable into the cavity. Softly holding it in place, press the tool to crimp the pin to the wire.
  5. Now join the main component with the rest of the connector by screwing them together. They should meet in the middle. 
  6. The last step will be to tighten the connection. Lightly pull on the connector to see if it is secure on the cable’s end.

How to assemble a PV system using solar connectors

When you need to connect two or more modules in series using MC4 connectors, all you need to do is click together male and female wires. This type of connection will increase the system’s voltage. For example, if the voltage of individual modules is equal to 18, two of them connected together will output 36. The current will not be affected.
When wiring in parallel, you need to connect the positive and negative leads with each other. This will increase the system’s current without affecting the voltage. For example, from 8 A for a single module it will go to 16 A when connected in pairs. Two male or female ends can’t connect, so it will require additional equipment, such as multibranch connectors. There are two types: the first takes two male connectors and outputs a single one that is also male, while the second does the same with female leads. Keep in mind you need a special unlocking tool to separate the modules. To do that, press the two extended posts on one end of the tool into the side of the female connector.
Illustrations – Marina Fionova


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