How To Choose The Correct DC Cable For Solar PV System

There are so many different types wires, and do you know how to choose the correct DC cable for your solar PV system?

Choosing the wrong type of wires or cables may result in overheating and loss of energy

In this guide, we will provide you with some easy to follow bullet points so you know exactly what to buy.

Cable Selections

Follow these steps to select the right cable:

  1. Ensure voltage rating of the cable equals to or greater than the voltage rating of the system
  2. Ensure the current rating can handle the current output of the system
  3. Ensure the cable is coated to withstand environmental abuse.
  4. Always check for voltage drop

Use the correct DC cable is important for performance and safety. The cable transfer energy from one component to another in order to convert solar energy into electric energy.

Things to pay attention to:

  • Cables Size (Gauge & Diameter)
  • Length of Cables
  • Cable Composition (Solid or Stranded)
  • Cables Material
  • Voltage and Current Rating

Solar Array AC Cable – Connects solar panels and junction box together, and they must be resistant to moisture, UV rays, and extreme temperature since its exposed in the environment

Battery Cable – Connects batteries together to form battery storage for solar power systems.

Appliances – Use conventional electrical wiring on a 120 V system

When To Use Thin Or Thick Cable?

If you wish to generate larger current and transfer it for a longer distance, ensure you buy thicker wires based on your system.

Cable Composition

Solid or Stranded?

Stranded cable is much more flexible so you can rearrange the cable and bend them without wearing it out.

Material

Copper and aluminum are most used for commercial and domestic installations.

Copper conducts current better than aluminum and it’s more flexible and can resist heat better than aluminum.

Aluminum wires are more rigid weaken when bent. Aluminum wires come in larger gauges and are mostly used for outdoor installation such as service entrances.

However, in PV applications copper wires are commonly used to prevent energy loss and it lasts longer than aluminum ones.

Use splice connector to connect copper and aluminium wires or cables together, use splice connector. Connecting each wire individually reduces susceptibility to corrosion.

Voltage & Current

Thicker wires have less resistance and can carry more voltage while using a long wire. If there is a way to combat voltage drop is to increase the wire gauge

For a 12V system, the cable is much thicker in order to carry more current. Learn more about the difference between the 12V and 24V systems here.

For a high voltage system, use a thinner cable since the DC current will drop. For a 24V system, the cable is thinner and cheaper.

Cable Length

The length of the cable is an important factor. The longer the wire is the better transfer of current, which also increases the cost based on the setup you have, and it also starts to lose more voltage through resistance and heat.

Please follow this rule of thumb to calculate the length of wire required at minimum to have the best system performance:

System current / 3 = cable size in squared mm

MM2 unit can be converted to AWG, please keep reading to know their differnces

AWG & MM2

American Wire Gauge (AWG) is a US standardized wire gauge system to note the diameter of rounded and non ferrous wires.

  • Bigger AWG number, the smaller the wire is
  • For every 6 gauge decreases, the wire diameter doubles
  • For every 3 gauge decreases will double the cross sectional area.

MM2 makes determine wire’s current carrying rating much easier.

Here is a quick reference:

  • 14 Gauge , 15 Amps max for general lighting setup
  • 12 Gauge , 20 Amps max for appliances
  • 10 Gauge , 30 Amps max for AC
  • 6-8 Gauge , 40-55 Amps max for large appliances
  • 1/0 – 3 Gauge , 100-150 Amps for feeder cable
  • 3/0 Gauge, 200 amps for service entrance cable (The wires connected to the load side of the meter enter the house or building)

Overheating Protection

Check the ratings of the cable to ensure it can withstand heat to prevent voltage drop, which leads to power loss.

Ying Xu

Graduated from the University of Kansas with an Aerospace Engineering degree & served 4 years as an US Air Force officer. Experienced with basic survival skills, weapon system security,  technical disaster recovery, and system troubleshooting

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