8 Tips for Wiring LED Lights

Diodes are electronic circuit components that pass electricity only in one direction. All emit light, but it usually isn’t visible. Because of the materials used in their construction, light-emitting diodes (LEDs) do give off light we can see, making them as useful as they are fascinating.

Today, bulbs incorporating large numbers of individual LEDs are fast replacing incandescent and fluorescent bulbs for home lighting. And with low-voltage LED lighting and strip lights, you have more ways than ever to add mood, color and accents to all parts of your home or car.

Wiring an individual LED to a power source is simple, and you can even do it with two potatoes.

Stick a penny and a galvanized nail deep into each potato so they aren’t touching, then use wires with alligator clips to connect the penny in one potato to the nail in the other. Clip one wire onto the free penny and another onto the free nail, then clip the other ends of the wires onto the terminal wires sticking out from an LED.

As soon as you make the final connection, power flows and the LED lights up! (If not, you need one or two more potatoes.)

Unless you’re a hobbyist, you probably won’t work with individual LEDs, only prewired fixtures, bulbs and strips. It’s worth remembering residential LED lighting works pretty much the same as a potato battery. It illustrates two important principles: Electricity can only flow in a closed loop (a circuit) so tight connections are crucial, and you need enough voltage (potatoes) to produce light.

Here are our tips for wiring LED lights:

Check the Voltage

LED lights and fixtures are typically low voltage, operating at less than 50 volts. Electrical receptacles provide power at 120V, so you’ll need a transformer to reduce line voltage to the level your lights require.

Sometimes the transformer comes with a lighting kit. If you have to purchase one, make sure the output voltage matches your light set. The most common are 12V and 24V, but 48V systems are also out there.

Get a Transformer With High Enough Power Output

Your transformer must have enough output power, measured in watts, to meet the lighting load.

To calculate the load, add the wattages of all the LEDs in the system, then tack on another 20 percent to calculate the minimum output of the transformer. The overage prevents transformer overload, which can cause it to overheat and start a fire.

Wattage for strip lighting is usually specified per foot of strip (typically four watts), so just measure the length of the strip and multiply by that factor.

Plan for Voltage Drop

Voltage drop occurs because of electrical resistance in the wiring, causing LEDs far from the power source to appear dull or fail to light altogether. This is common when installing LED landscape lighting, but can also occur with extra-long strip lighting.

You can minimize it by increasing the wire gauge, because fatter wires offer less resistance. If you’re using 12-gauge wire, increase it to 10-gauge. That should make the lights farther away shine as brightly as those nearby.

On large properties, to avoid voltage drop, you can often wire fixtures on two or more separate circuits that feed back to the power source. Sometimes, though, there’s no alternative to splitting a long lighting loop in two and powering each loop from a separate transformer.

Similarly, if you experience voltage drop with strip lighting, you may need to reduce the length of the strip.

Wire Fixtures in Parallel

Wiring in parallel provides the most even voltage distribution to each LED fixture in a circuit. In practical terms, this usually means splicing individual strings of lights onto a main wire that leads to the power source. That’s how devices are wired into a 120V residential circuit.

Use the Right Wire Connectors

Interior lighting systems and strip lights usually come with their own connectors and instructions on using them. All you really need to do is follow the instructions, but be sure to give an extra push to make sure the connector snaps together. If one connector is loose, the entire chain may fail to come on.

When installing landscape lighting, you usually secure wires with snap-on or screw-on connectors. Use waterproof connectors safe to install underground. Bury the connector for each light at the base of the fixture so you can find it easily. The best outdoor connectors contain gel that prevents moisture from coming in contact with the wires.

Avoid Crossed Connections

Unlike 120V electrical circuits, low-voltage circuits for LED lighting use stranded wire. It’s a common mistake to leave one or two strands hanging loose when you connect the wire to a controller. The errant strands then contact another terminal and cause a short.

Avoid this by diligently twisting the strands together into a tight knot after stripping off the wire insulation. If you have to disconnect a wire for some reason, be sure to twist it tightly before reconnecting.

Use Wire Splitters

Another common DIY mistake is overloading a controller terminal with more wires than it’s designed to handle. In most cases, that’s only one. This is a fire hazard if one of the wires is loosely attached, and can also cause voltage drop in the loose wire.

Avoid this by using wire splitters with a single terminal connection and multiple inputs for wires if you need to connect two or more lighting circuits to one transformer.

Install LED Strip Dimmers After the Transformer

Dimming your LED strip lights with a remote control is a handy feature, and the component you need to do it is called a pulse width modulation (PWM) dimmer.

It doesn’t plug into the wall receptacle like a conventional dimmer; it’s wired into the 12V circuit after the transformer. You simply feed the wires from the transformer into the dimmer input terminals, then feed the wires for the strip circuit into the output terminals.