What is the difference between Thhn and PV wire?

THHN (Thermoplastic High Heat-resistant Nylon-coated) wire and PV (Photovoltaic) wire are both types of electrical cables, but they are designed for different applications and have distinct characteristics:

Application:

THHN wire: THHN wire is commonly used in indoor wiring applications, such as residential and commercial buildings. It is suitable for general-purpose wiring in dry or damp locations, including conduit and cable trays.

PV wire: PV wire, also known as solar cable, is specifically designed for use in photovoltaic power systems, such as solar panel installations. It is used to connect solar panels to inverters, combiner boxes, and other components of solar energy systems.

Construction:

THHN wire: THHN wire typically consists of copper conductors with PVC (Polyvinyl Chloride) insulation and a nylon coating for added protection and durability. It is available in various conductor sizes and insulation thicknesses.

PV wire: PV wire is constructed using materials that are resistant to UV radiation, extreme temperatures, and outdoor environments. It typically features tinned copper conductors with cross-linked polyethylene (XLPE) insulation and a special UV-resistant jacket. PV wire is available in specific sizes and configurations to meet the requirements of solar power systems.

Temperature and Environmental Ratings:

THHN wire: THHN wire is rated for use in temperatures up to 90°C (194°F) in dry locations and up to 75°C (167°F) in wet locations. It is not designed for outdoor or direct sunlight exposure.

PV wire: PV wire is specifically engineered to withstand outdoor conditions, including exposure to sunlight, rain, snow, and extreme temperatures. It is rated for use in temperatures ranging from -40°C (-40°F) to 90°C (194°F) and is UV resistant to prevent degradation from sunlight exposure.

Certifications and Standards:

Both THHN wire and PV wire may need to meet specific certifications and standards depending on the application and jurisdiction. PV wire is often required to comply with industry standards such as UL 4703 for solar cables.