This web page does an OK job defining terms - https://www.electronicsforu.com/mar...-nominal-voltage-voc-vmp-isc-imp-solar-panels Vmp = Voltage at maximum power - this is more representative of when the panels are producing power.Imp - Current at maximum power - this is more representative of when the panels are producing power.The VoC is used so you don't exceed the maximum voltage the Charge Controller can handle - this can go up in very cold weather when there's no active power (yet) - so you want to keep it in mind when designing a system.Wire for PV power transmission .... I wouldn't overthink it unless you are doing over 200ft lenghts. For 'regular lengths' such as you would find in home wiring from the main panel to circuits around the house - e.g. up to 150ft... regular amps / awg are fine in my experience. You'll notice that no one does 'special wiring' for a regular home worrying about 2% lossThe basic for awg / amps for home wiring (e.g. up to 150ft of PV transmission):14awg = 15a max12awg = 20a max10awg = 30a max * Panels have 10awg pigtails (30amps) but typically you don't want to go right up to 30amps ... say 25a max.8 awg = 40a max6 awg = 50a max4 awg = 80a maxetc... standard wire sizes per amps will do you OK.However, if you want to try for just a bit more efficiency, there's nothing wrong with oversizing wire - its just expensive for small gain.The #1 (by far) loss of efficiency in my system is the DC -> AC inverters. The wiring losses (up to 150ft) is so small I can't detect it, even the charge/discharge loss to the battery looks 1% max?and if I don't keep power consumption % up higher on the inverters, they can sink down to 20% loss. To illustrate - I produce 18,000kwh/year but loose kwh/year to inverter losses. If you want to spend money - do it on an efficient inverters is my best advice
Solar cables & wires are a type of wire used in photovoltaic system equipment to generate electricity. Solar cables connect solar panels to other electrical devices in the design, allowing power to be transferred from one point to another when necessary. They incorporate circuit components and act as conduits for power transmission.
Typically, you install solar panels on a roof or elevated structure to avoid obstructions on the ground and to better receive the sun's rays. These panels absorb solar energy and convert it into usable electricity. When the sun's energy is converted into usable electricity, solar wires & cables carry it to a power unit inverter that converts direct current to alternating current for eventual storage in batteries.
A well-planned and properly installed network of solar cables & wires ensures the safe and smooth operation of your PV system. Photovoltaic wiring design requires the correct use of solar cables. If you are new to photovoltaic systems, it is essential to understand the basics of solar wire & cables.
Solar Wires VS Solar Cables
Although people use the terms solar wire and solar cable interchangeably, they are different. Solar wires refers to a single conductor, while solar cable is a combination of several conductors or wires held together by a sheath.
Solar Wires
There are many types of solar wires used to connect photovoltaic system components. They contain four main elements: solar panels, inverters, charge controllers and batteries. Selecting the correct type of solar wire in a PV system is critical to its operation and efficiency. For example, using the wrong solar cord may not provide the proper voltage and power to the electrical unit, causing the battery pack to not fully charge.
Generally, there are two types of solar panel wires, solid core or stranded. Specifically, solid or stranded wire contains a single metal core, while stranded wire consists of multiple twisted conductors.
The boot insulates the individual wires, but also has bare wires. Solid wire styles are recommended for static applications, especially household wiring. Solid wire has a tighter diameter than stranded wire and has the same load carrying capacity. The cost per wire is lower, but only for small gauges.
Stranded solar wires consists of multiple conductors twisted together and covered with a sheath to form a ground wire. Twisted solar wires are more flexible and can withstand frequent movement. If you are installing your solar system in a location with high winds or periodic vibrations, standard wire is recommended. Stranded wire conducts electricity better due to the multiple conductors in a single run. However, stranded wire has a larger diameter and costs more than solid wire. Standard wire is the best choice for large outdoor installations.
Structure Of Wire
Solar wires can also be classified according to the conductors used. Aluminum and copper solar wires are commonly used in home and commercial installations. Copper wire has excellent electrical conductivity compared to aluminum. A copper conductor solar wire of the same size can carry more current than an aluminum wire. Copper is flexible and better heat resistant. It supports both indoor and outdoor applications. However, copper wire is more expensive. Solar panel cables Meanwhile, cheaper aluminum wire is both stiffer and weaker when bent. They are larger in size and are often used in outdoor installations such as service entrances.
Solar Wire Insulation
Solar wires also vary in insulation. The jacket protects the cable from the attack and effects of moisture, heat, chemicals, water and UV rays. Common insulation types include:
THHN cable is suitable for applications installed in dry indoor conditions;
TW, THW and THWN cable are suitable for conduit applications installed in wet, indoor or outdoor conditions;
UF and USE (Underground Service Entrance) for wet underground wiring, but not limited to underground applications;
THWN-2 is inexpensive for indoor applications. Since it goes through the catheter, it doesn't have to be UV resistant. THWN-2 can be run directly to the main service panel. It can be used in both DC and AC circuits, but the size will change after the wiring passes through the inverter;
RHW-2, PV wire and USE-2 solar cable for wet outdoor applications. These wires are ideal for connecting solar panels, service terminal connections, and underground service entrances. The sheathing of the PV wire and USE-2 withstands extreme UV exposure and is moisture resistant. In addition, the photovoltaic lines are equipped with additional insulation.
Wire Color Guide
Color-coded solar wires make it easier to execute and draw wire plans. The wire colors indicate their purpose and function in the solar system. This is also critical for future troubleshooting and repairs. The National Electrical Code specifies conductor insulation and application. Alternating current (AC) and direct current (DC) are color coded differently. Here's a quick color-coded guide for easy wire installation.
AC Power Application
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Red, black or other colors for non-grounded thermal applications
White is the ground conductor
Green or bare, for equipment grounding
DC Power Application
Red is positive
White is the negative or ground conductor
Green or bare, for equipment grounding
Be sure to follow National Electrical Code (NEC) recommendations when installing your electrical system. Also, if you're not sure which conductor and insulation to use in a particular application, it's best to seek the help of a certified electrician.
Wire Rating And Thickness
PV wires are rated based on their maximum current capacity. Solar panels with higher amperage (current) require thicker solar wires with higher ratings. Just be sure to check the amperage rating of your system and use wire that can handle the load. For example, if it draws 9 amps, use a 9 amp or higher wire (11 or 12 amps).
Choosing a solar wire with a lower rating will result in a voltage drop. Over time, it can cause overheating and even increase the risk of fire.
The thickness of solar wire is usually related to its amperage - thicker wire; higher amplifier capacity. As a rule of thumb, always use wires that are thick enough, or slightly thicker, to handle the occasional power surge. Identify the device with the highest current and choose a wire that can handle this current. To better guide you, use the wire size estimators available online.
Use an American Wire Gauge (AWG) ruler to measure the size of the solar PV copper wire. In an AWG system, the cables get smaller and smaller as the number of AWGs increases. Therefore, 2 AWG solar wire has a larger diameter than 12 AWG wire. However, wire size is inversely proportional to the amperage of the wire. For example, a 2 AWG solar cable has 95 amps, while a 12 AWG solar wire has 20 amps.
Wire Length
In addition to the rating and thickness of your solar wire, consider its length. The longer the power is delivered, the higher the amperage drawn. So always use a slightly thicker wire for extra safety, and if it's broken, go crazy.
For example, if the installation runs 5 meters, with a maximum current of 10 amps and an acceptable cable loss of 3%, then 6mm solar cable can be used. However, if the same installation runs 15 meters, 25mm solar cable will be required. Likewise, using lower rated wire increases the risk of voltage drop, overheating and fire. Electricians also recommend preparing for future load requirements; therefore, it is always safe to use thicker wires in the initial installation of solar cables.
Solar Cable
Solar cables consist of several insulated wires wrapped in an outer sheath. Professionals use them to interconnect solar panels and other components of photovoltaic systems. They can handle high UV radiation temperatures and are highly weather resistant. Typically, they are mounted on the outside or inside of solar panels.
The diameter of a cable depends on the number of conductors it contains. Therefore, the classification of solar wires is based on the number and specifications of the wires. Generally speaking, three types of cables are used in photovoltaic systems: DC solar cables, solar DC main cables, and solar AC connection cables.
Solar Cable Size Guide
Cable sizing is critical for all solar power systems. If the cable can&#;t cope with the demand there&#;s a risk of of overheating, blown fuse or worst case, a fire. No matter what solar power system you are setting up, cable size is of paramount importance.
You can always get a larger, longer cable than needed, but never smaller. There are two factors to consider, the solar panel rating and the distance between the panels and loads. The higher the watt panel capacity, the thicker the cable required. The further the panels and the loads are from each other, the longer and thicker the cable.
As power goes from the panels to the inverter, the cable makes certain energy loss is kept to a minimum. The thicker the cable the better. Other factors to consider are the following.
Protection: the cable must have protection to keep animals from tearing the cover and exposing the wires.
Short circuit resistance: quality solar cables have anti-short circuit features.
Fireproof: look for solar cables that can run at high temperatures without bursting into flames.
Chemical resistant: most cables provide some form of protection against acid and other chemicals.
Durability: the more durable the cable, the better.
Temperature working range: solar cables are designed to work under specific temperature ranges. Find one that can handle extreme levels of cold and heat.