Solar panels have short lengths of cables and connectors installed when purchased. To connect the solar panels in either a series or in a parallel array to the charge controller, you will require additional lengths of solar cable and connectors. Trying to save money on buying cheap solar cables to connect your system is a common mistake by DIY installers.
Use a solar cable that carries the Underwriters Laboratory (UL) markings defining it as suitable for use in external photovoltaic installations. These cables must be:
- Flexible
- UV resistant
- Flame retardant
- Rodent repellant
- Water-resistant
- A minimum DC Voltage of 1500 V DC
The installation of a solar panel array at your home is an investment that should last for at least twenty-five to thirty years. The most vulnerable part of a solar power system is the exposure of the external wiring and connectors to the harsh elements.
How are UL-rated PV (photovoltaic) wires or cables made, and why are they so expensive?
Why Is The Right Solar Cable So Expensive?
The best metals for electrical wire cable are Silver, Copper, and Aluminum. Silver is the best but also very expensive and would not be commercially viable for the installation of domestic solar systems. Copper is the best alternative and much more affordable than Silver.
Aluminum wire is often available in the market as a low-cost alternative. Copper-plated aluminum is also on offer to seduce the frugal buyer but should be avoided at all costs.
If you are running a short-term trial setup, you can use lower-cost wire just to prove your test of concept, but for long-term installations, pure Copper wire is the best.
Solar cables are bundles of thin strands of pure copper wire to provide flexibility and maximum current carrying capacity (lowest resistance). Stranded wire conducts the flow of electrons better than a single solid wire strand of the same gauge.
Types of Cables
The wire is produced to various thicknesses and rated in accordance with the Amperage at a certain diameter (gauge) and temperature.
The bigger the diameter of the combined strands of copper wire, the less the resistance the electrons will have inflowing from the solar panels to the charge controller.
The design of your solar installation will consider how far the solar panels are from the charge controller and how much the voltage drop will be over such a distance.
Many online calculators will assist you in determining the correct gauge wire to use for your design. The cost of the wire increases as the diameter gauge required increases.
See also: How to install solar panels (Detailed Step-By-Step Guide)
Which Solar Cable To Choose
As a rule, always go for a heavier gauge wire. The initial investment will be higher, but the payback will be in system efficiency.
An inner protective coating of the copper wire strands affords an additional layer of protection and flexibility. It prevents moisture ingress and ensures that the bundle of stranded wire is compact.
An outer Silicon-based plastic sleeve protects the wire against UV radiation and must be fire retardant and not be attractive for rodents to gnaw at.
Extreme temperatures and the relentless attack of the sun on the cabling require you to select the correct gauge UL-rated PV cable at the outset. The most commonly used wire gauge connecting the solar array to the charge controller is 10 AWG.
In Marine installations, the option of using Tinned Copper wire affords additional protection against corrosion.
Buy the thickest gauge UL-rated PV-specific wire you can afford for your project. Look at ways to limit the distance from the solar array to the charge controller to save money, but don’t go cheap on the solar cabling.
Upsizing Cables For Your Solar Installation
Installing a solar power system at home or in commercial properties makes sound financial sense. As the cost of PV panels and components has reduced to a level where solar power has the lowest cost per kW/h of any form of energy, the payback period is less than five years.
For a five-year payback on a thirty-year investment, you will be making a healthy return on investment.
Most of the budget will be for the solar panels, charge controllers, inverters, and battery banks but do not neglect to buy the best possible solar cables to join the system up. Poor quality cable or undersized cables can destroy your solar panels or even your house due to overheating resulting in fire.
Get professional advice and installation assistance. All solar system contractors are fully qualified and certified installers. Let a professional guide you with the design and the installation.
Plan for the future expansion of your solar power generation capacity upfront. Do not use the minimum gauge PV wire for the installation.
It is always more expensive to rewire than to go bigger from the beginning.
What Is The Most Commonly Used Solar Wire?
The UL specification 4703 applies to solar cables and is specific to the wiring up of the solar panels in either series or parallel and the connection to the charge controller. The wire is designed to withstand exposure to UV and for underground installation.
The most commonly used size conductor in domestic installations is 10 AWG. For future expansion or upsizing, the conductor Amperage, 6 AWG, and 8 AWG are also used. The smallest diameter conductors in compliance with UL 4703 are 18 AWG.
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The wire bundles are double insulated with cross-linked Polyethylene and are rated to withstand 90 degrees Celsius in wet conditions and 150 degrees Celsius in dry conditions.
The insulation is resistant to sunlight, ozone, Ultra Violet light, flame, and moisture and is not tasty for rodents. The cable is available in maximum voltage ratings of 600 V, 1000 V, and 2000 V.
Your solar system installer can purchase in bulk and will be able to give you the best pricing and quality for the system.
The installer will also provide you with an installation warranty and will thus ensure that they use the correct size and type of solar cables.
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