Solar Panels: Cables and Connectors
Solar systems are electrical systems and its different parts must have to be connected together in some ways. This is done in ways that resemble but significantly differ from the ways other electrical systems are connected.
Solar cables or PV wires are the types of wires used to connect solar panels together and to other electrical components, like solar controllers, chargers, inverters, etc, that use them. The choice of solar cables are critical to the health of a solar energy system. The right choice of cables must be made otherwise the system will not function properly or will be prematurely damaged or the battery banks may not charge well or at all.
Since they are generally laid outdoors and under the sunlight, they are designed to be weather-resistant and to work within a large temperature range. They are also designed to be resistant to ultra violet rays produced by the sun alongside visible sunlight.
They are also insulated to protect against short circuits and ground faults.
These cables are often rated by the maximum amount of current (in amps) that can travel through that wire. This is a major consideration. In choosing a PV wire, this rating must not be exceeded. The higher the current, the thicker the required PV wire. If the system is to produce 10A, a 10A wire is needed. Or slightly above but never below. Otherwise, a lesser-rated wire will cause the voltage of the panels to drop. The wires may heat up and catch fire causing damage to the solar system, domestic accidents and most certainly, financial losses.
Thickness and Length
The power rating of a solar cable means that higher power PV wire will be thicker and in turn, a thicker PV wire will costs more than thinner one. The thickness is necessary bearing in mind the vulnerability of the area to lightning attacks and the system to power surges. The best choice in thickness is the one that can cope with the highest current-drawing appliance intended to use to system.
Length is also a consideration, not only for distance sake but because if the PV wire is longer than average and connected to a high current appliance, a higher power wire will be required. And as the length of a cable increases, its power rating will increase as well.
Also, using a thicker cable will allow for the future incorporation of high-power appliances into the system.
Connectors are needed to connect multiple solar panels together into a string. (Single panels do not need connectors.) They are available in 'male' and 'female' types built to be snapped together. There are many types of PV connectors, Amphenol, H4, MC3, Tyco Solarlok, PV, the SMK and the MC4. They come in T-, U-, X- or Y- Joints. The MC4 is the most commonly used connector in the solar system industry. Most modern panels are built to use the MC4 connector.
Specifications of the MC4 Connector
The original manufacturer is Multi-Contact USA. The company is now owned by a Swiss company Stäubli Electrical Connectors.
It is rated at a maximum power of 30A.
It is rated at a maximum voltage of 1,000V (600VDC UL)
Its temperature range is between -40 degrees C to +90 degrees C.
Protection Class: Class II
Contact Resistance: < 0.5 milli ohms
Protection Degree: IP67 IP2X (unmated)
Wire Size Range: 10, 12, and 14 AWG (6 sq mm, 4 sq mm, and 2.5 sq mm)
Insulation Material: PA/PC
Flame Class: UL94-VO, UL94-VA
Contact Material: Silver Plated Copper
MC4 Extension Cable
MC4 extension cables are used to connect the power from the connectors that have been used to connect the panels to either a circuit breaker or a charge controller. Otherwise they serve the role of PV wires and cables as already described above.
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