It is time to look at your solar panel wiring. It’s an important part of your solar set up. You now have decided on the solar panels that you want to use, and chosen the other ancillary parts for your solar system.
Wiring the solar panels together is a step that brings together the whole solar system to achieve maximum efficiency. You need to consider the components of the whole system in deciding which wire size to use for the solar system.
If you install your own panels and racking make sure that its wiring connections are checked as safely installed and wired into the electrical meter by a licensed electrician familiar with solar PV power systems.
Before we get started, watch the video below on solar panel wiring. Note that each worker is wearing a fall arrest harness. The video considers the issues of best inverter type and wiring considerations for that choice.
Choose the Right Wire for your Solar System
The type of solar wire that you choose influences the efficiency of your solar system.
Solar wires are generally classified into two types:
Choose the right size of wire to ensure that the solar system functions effectively where there is no damage to the system components or the appliances connected to the solar system. If for instance the PV wire used in your solar system is too small, the resistance in the wire is higher then the battery will not be charged at the optimum level. This can lead to the appliances connected to the solar system not working effectively.
Solar Wire Types
Electrical wiring is categorized by the conductor type used. It can be a single metal wire core with a single-stranded conductor or it can be a multiple wire core with a multi-stranded conductor. The multiple stranded wire is better rated for performance in continuous vibration conditions, like that in trains, cars, planes, and boats.
For your domestic solar power system, choose a single strand conductor type wire. Solar systems in areas that experience consistently high winds, then use a multi-stranded conductor type wire that is more flexible and durable.
PV Wire Ratings
Wiring used in a solar systems are also rated according to the current (amperage - amp) carried by them. This rating specifies the maximum amps for the wire which is the maximum amount of current that can travel through that particular wire. Keep this in mind when planning your solar panel wiring. The greater the thickness of the wire the greater the amps that it can support. The higher the current (amps) produced by your solar system, the thicker the PV wire needs to be. For example, if your system generates 9 amperes of direct current, then you require wire that is capable of carrying 9 amps or higher to the system.
There are drawbacks to not following the PV wire ratings in your solar system. If you use wire that is rated at lesser amps than what is being produced by your solar system, it causes your wiring to heat up due to their greater resistance. Hot wires can even ignite a fire that can damage not only the solar system but also your connected appliances and house. The wire should be rated to withstand the maximum amount of current that will be flowing through it. A consequence of using undersized wires is that you will face a voltage drop.
Solar Wire Thickness
A thicker PV wire can support a higher amount of current (amps) but it is more expensive than a thinner wire. The extra initial cost for larger wires will provide a safeguard against any sudden power surges. You might accept the risk of a cheap undersized wire but be aware this risks suffering possible damages to the system when using a thinner wire than required.
You can determine what thickness of wire is best for your system is by calculating the highest amount of current (amp) likely to be used among your appliances. You might then use that wire size for the entire system.
You could use a solar cable size calculator to find the cable size. Click here or on the picture below for an online calculator.
How to use the Free Solar Cable Size Calculator
A solar wire size calculator calculates the wire size of the copper wire required for your solar system. You simply enter the various electrical parameters of the solar array like power, voltage, and current, along with the cable’s working temperature conditions.
When selecting the cable or wire type, look at both of the conditions; the calculated wire diameter and rated maximum amps for power transmission. In some cases the wire diameter selected has a lower calculated amps rating, so you need to choose a wire with higher wire diameter that corresponds to the required calculated amp rating.
PV Wire Length
The length of the wire being used in your solar system is another factor to consider in solar panel wiring. If the PV wire to be used is longer than average and is connected to a high amp appliance, the wire needs to be rated at higher amps as well. A lower amp wire in this scenario might lead to a voltage drop, causing the wire to heat up.
Let’s work through a practical example. If you have a 40 amp appliance and you are using a 40 amp wire but it has considerable run in length, so the resistance in the wire is greater. That means there is a risk of a voltage drop. There needs to be a buffer of at least 35% in the size of the PV wire. So, for a 40 amp appliance try using a 55-58 amp wire.
The amp rating on the wire is proportional to its length, so as a precaution you should install using a slightly thicker wire. Using a thicker wire at installation means you can use a higher current (amp) appliance in future. The precaution will save you from upgrading or rewiring your solar panel at an earlier time in the future. Let's explain how the length of the wire and the amps rating are related to each other. If your solar panel or the battery bank is generating 7 amps and the wire length is 4.6m, then after adding the 35% buffer the amp calculated of the wire comes out to be: 7 + (35% of 7) = 9.45 amps or 10 amps.
The wires used from the breaker panel to an individual appliance must be capable of handling the current (amps) of that particular appliance. However, the wire from the battery to the rest of the photovoltaic components should be able to handle the combined amps of all such individual appliance, plus the buffer of 35% or more.
When you are choosing your solar panel wiring, you will find that following these basic rules as safety guidelines will increase the efficiency of the solar system and eliminate the chances of any damages.
Solar Panel Wiring
After you select the appropriate wire size, there are some fine points to the wiring. If you have high voltage rated appliances connected to the solar power system, then the PV panel wiring arrangement must support those appliances with sufficiently high enough voltage.
A higher amp solar wiring arrangement can facilitate faster charging of your batteries in the case of a few low available daylight hours. If your solar system is powering several appliances in one go, then the wiring must permit the higher watts and volts for larger appliances with sufficient amps to charge the batteries.
Wiring Joins The Solar Panels And Batteries
The wiring of the solar panels in a 12-48 volt off-grid solar system can be done in three ways:
These circuits have the current moving across multiple paths. Where one item or appliance in the circuit is turned off, the current will bypass it and access the parallel circuit appliances that are connected.
Parallel circuit wiring is mostly used for household solar panel wiring. In a parallel circuit, the amps of each panel are added together but the volts remain the same. So, if in a four solar panel array in a parallel circuit each panel is rated at 12 volts and 8 amps, the array taken together would be 12 volts and 32 amps.
In these circuits, the current passes along a single path. Unlike a parallel circuit, this one is a continuous loop. A break in the circuit at any point will stop the entire series completely. The current that is moving along the single path needs to flow through all the loads attached to the series. A string of Christmas lights best demonstrates the working of the series circuit, where a fault in even one bulb stops the functioning of the entire string.
In a series circuit, the voltage is additive, but the amps are not, which is the exact opposite of a circuit wiring. So, if in a four-panel array in a series circuit, each panel is rated at 12 volts and 8 amps, we would have 48 volts and 8 amps for the full array. While doing the solar panel wiring in a series circuit, the positive terminal of the first solar panel is connected to the negative terminal of the next solar panel and so on. On the other hand, while wiring the solar panels in a parallel circuit, all the positive terminals of the solar panels are connected together, and the negatives are connected together separately.
Wire management in a solar system is important to get right. However, it’s often the most overlooked step. You system’s wiring must be done in an organized manner if it is to withstand the extreme weather conditions. Tradesman like wiring should be installed with a protective casing, be properly labeled, not intercept any component with sharp edges and you should confirm by inspection that there is not excessive bending of wires during the installation.
When you do wire your panels into the system or get the wiring done for you, make sure that you have a qualified electrician look at it before it goes live. The electrician who checks the system wiring needs to have working experience on solar panel installations, to effectively check and complete the wiring installation before making the connection.
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