What Is a PV Wire and Its Role in Solar Energy Systems?
Wire management is a key aspect of solar energy system installation. It involves ensuring that wires are properly routed, supported, and protected against harsh environments and environmental hazards.
PV wire is different from USE-2 wire, as it has specific voltage and amperage ratings for both grounded and ungrounded interconnections. It also features a thicker insulation and jacket for improved sunlight resistance.
What is a PV wire?
A pv wire is a single-conductor wire that runs from your solar panels to the combiner box or junction box. It can handle higher voltages and more amperage than other building wire types. This type of cable must meet specific standards to ensure that it is able to handle the demands of your PV system.
It’s important to choose the right wire for your solar panel system because a low-rated cable may not be able to deliver enough electricity to power your panels or charge your battery bank. A wire that’s too thin could also overheat and damage your system or even cause a fire.
In addition to meeting standard insulation and jacket requirements, a PV wire must also undergo more rigorous tests than other building wire types. It must pass flame, overload, crush, impact, and mechanical abuse tests to ensure that it can withstand the harsh conditions in which it’s used. In addition, it must have better sunlight resistance, flexibility at low temperatures, and temperature ratings to ensure that it can withstand the sun’s intense heat.
While THHN (Type THWN) wire is another common choice for solar panel wiring, it cannot replace USE-2 or PV wire because it does not meet the minimum standards for these types of applications. It does not pass the crushing, impact, and flame test required for USE-2 or PV wire.
Why is a PV wire important?
There are two main wires in a PV system: an equipment grounding conductor and the power supply wire. The EGC, as it’s commonly called, connects all the metal components in a PV system to ground so that electricity doesn’t short out on them and create a fire hazard or injury. The power supply wire carries current from the modules to the inverter where it’s converted into usable electric power.
Depending on the type of inverter, this can be either DC or AC. Both wires are required to be a specific thickness in order to handle the voltages and amperage of the solar panels. The PV wire is typically stranded rather than solid in order to be more flexible and allow it to bend.
PV wire is also more able to resist sunlight and can be direct buried according to the NEC, so it’s better suited for outdoor installations. Additionally, PV wire must pass more stringent testing requirements for sunlight resistance and low temperature flexibility, including 720 hours weatherometer and -40degC cold chamber conditioning.
Properly supporting and managing your PV system’s wiring can go a long way in increasing its longevity. Choose stainless steel wire clips, UV-stabilized composite wire ties and conduit or cable trays to ensure your wiring stays in place and protected from physical damage. This will help you avoid costly repairs and keep your customers happy for years to come!
What is the role of a PV wire?
The role of a PV wire is to carry electrical energy from the solar panels to the inverter and battery, and to then deliver it to appliances. The wiring must be properly sized to handle the load and ensure the system is working as designed and not overheating or causing other problems.
The wiring used for PV systems is typically UL Listed Type USE-2, UL Listed THWN-2, or UL 4703. USE-2 wire uses XLPE insulation with bare copper, tinned copper, or aluminum conductors. This wiring is crush, oil, gas, and impact-resistant, making it ideal for PV systems. It also has a high temperature rating and is suitable for buried or wet conditions.
For the equipment grounding, installers traditionally run a solid AWG 6 bare copper wire from module to module and rack to rack, then down to the junction box or combiner box. This is sturdy enough to stand up to rodent gnawing and the elements, and can be encased in PV wire (or USE-2) jackets for additional protection and longevity.
For the DC side of a PV system (DC loads, charge controllers, and inverter inputs), most people use a THWN-2 or USE-2 building wire with a temperature rating of 90 degrees Celsius. This is more than sufficient for the voltages and currents needed to power most appliances.
How do I install a PV wire?
Most solar equipment suppliers don’t include wires with the panels because it’s up to installers or homeowners to select appropriate cable for the conditions and length needed. Choosing the right wire depends on many factors, such as its conductor material and thickness, its environmental characteristics and its ability to withstand power surges.
For example, copper is a more conductive metal than aluminum and can carry higher amounts of current. Thicker copper wires can also resist bending and flexing better than thinner ones.
Generally, the first thing you need to do is identify the maximum current capacity of your appliances and select a wire capable of handling that amount. You can use a wire sizing estimator available online to help with this process.
Then choose a type of wire that can withstand the conditions you’re likely to encounter, such as PV wire or THHN. PV wire has a thicker insulation and jacket than THHN, making it more resistant to sunlight, flames, and low temperatures.
When you’re ready to install the wires, you can connect the module leads to a junction or combiner box. If the distance between the junction or combiner box and the end of a string is too long, you can add an extension known as a “near-end run.” To protect the cables from rodents and other elements, you’ll want to put them in a wire tray, which you can attach to the modules or to a rail.