As LED lighting becomes more commonplace, laws and regulations on low voltage installations are being tightened in order to protect homes and businesses. David Boultbee, Technical Consultant at Ultra LEDs, gives his advice for installing low voltage LEDs safely
Because they generally run at a low voltage, LEDs are often considered a much safer option compared to halogen and incandescent lighting, as there is generally a lower risk of electric shocks. However, low voltage circuits can sometimes be subject to overcurrent conditions, and their cables and fixtures are often not protected, which can lead to fires. That is why it is important to install LED lights correctly.
Below, I will discuss the five things you will need to bear in mind when shopping for, and installing, low voltage LED lights.
Choose the Correct Wire
When a current passes through a wire, it creates heat. Most cables are insulated with PVC and have a melting point of 80°C. However, a temperature beyond this can cause the insulation in the wire to melt. When this happens, the conductors can often touch, leading to a short circuit which can cause injury or fire.
Therefore, it is important to choose the correct wire for your low voltage circuit in order to protect it from overheating. The current carrying capacity of a wire plays a big part in how well it can handle heat and, although there isn’t a single standard that wires must comply with, the main thing to look for is wire thickness, which is measured in AWG. The smaller the AWG, the thicker the wire, which means the current capacity is higher and it’s less likely to overheat.
You can calculate the thickness of wire needed for your job by adding up the amount of current in the circuit and choosing a wire that can handle at least 20 per cent more than its designed load. This can vary by manufacturer, so it is essential to check the manufacturer’s rating of wires and buy from a reputable source where you can so you can be confident that the wire meets its stated specification.
Protect Wires With a Fuse
IET Wiring Regulations BS 7671:2018 states that low voltage wiring should be protected by a failsafe device, like a fuse, in order to protect the conductors further on in the circuit. There is often some confusion that a fuse on the high voltage side will offer protection on the low voltage side, but this is not the case, and a low voltage fuse should always be present in a low voltage circuit.
You can calculate the size of fuse you will need by looking at the smallest conductor connected after it. Try to choose a fuse one rating below the conductor’s capacity. Once you have chosen your fuse, you should connect it to the positive wire as close to the power source as possible.
If you have more than one wire connected to a high-power driver, you can use multiple fuses and give each branch its own fuse. However, you will need to ensure that these fuses are of different sizes so it’s clear which one will blow for a given fault. This will also make identifying the fault much easier.
Pick a High-quality Driver
Many over-current faults can occur in a situation that is not detected as a short circuit. An LED driver will usually help to correct a high voltage and acts as an extra layer of protection against over-current conditions. A high-quality driver will usually be better tested than a low-quality version and will run at a cooler temperature. It may also offer better protection against fault conditions, such as over-current, high temperatures and short circuit. Therefore, you should make sure you buy your driver from a reputable seller. However, this should not be relied upon as the only protection method, so a driver should be used alongside a fuse, rather than in place of one.
Find the Right Surface
LEDs can get hot even in normal operation, so it is important that they are installed on a surface that can help to dissipate some of that warmth. A metal surface is great for this, as the material is a good conductor of heat, which can help prevent over-heating and lower the risk of fire. Ideally, LED light strips will be installed in an aluminium profile or extrusion that is designed for this purpose.
It is important to be conservative when installing low voltage lighting. Try not to bundle cables up, as this can cause them to trap heat. To avoid this, keep them separate and clip the cables to their metal surface. You should also try to limit the current in circuit branches to three to four amps (seven amps for main feeds). Where you can, use a higher voltage system, as a 24-volt system will deliver the same power of a 12-volt system, for half the current, reducing the risk of over-current conditions.
This information is intended for guidance only and any electrical installation should always be designed and verified by suitably qualified personnel.