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Tech Talk – Voltage Drop and Wire Gauge

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In our last Tech Talk, we covered testing a Vivid Pixel fixture.

This week, we’re going to cover voltage drop! It’s important to understand voltage drop, and how wire gauge affects it, when determining distance between your fixture and the power supply.

What Is Voltage Drop?

Voltage drop occurs when the gauge of the wire from the power supply to the fixture is too small to carry the current necessary to power it. In some cases, this can cause your fixture to appear slightly dim or show colors that look somewhat “dirty”. In other cases, your fixture can experience a “brown out”.  This is identified by muddy colors or very dim illumination. A brown out is a very serious issue, and will cause permanent damage to your fixture. This is why it’s extremely important to calculate for voltage drop.

How Do I Avoid Voltage Drop?

When you’re determining the distance between your fixture and power supply, you’ll have to calculate for voltage drop. The voltage drop percentage is dependant on the length of the wire, the gauge of the wire, and the current draw of your fixture.

Generally speaking, the thicker the gauge of your wire, the more power can travel through, and you’ll have a lower voltage drop percentage.

Our LED Neon Flex fixtures generally have an 18AWG wire. The exceptions are Seamless Vivid RGB fixtures which have a 20AWG lead wire, and Landscape Flex fixtures which have a 16AWG lead wire. Vivid RGB fixtures assembled with Snap Connector leads will have an 18AWG wire. If the voltage drop percentage is too high with an 18AWG wire, you can connect a larger gauge wire to our lead wires to lower the percentage.

LED Neon Flex fixtures have a maximum tolerance of 10% voltage drop. Ideally, however, you want to have the lowest voltage drop percentage possible, as even 10% can be pushing your luck. There’s no reason to risk a brown out when you can easily remedy the situation with a larger gauge wire.

To use a larger gauge wire, connect it to the lead wire of your fixture. If you’re concerned about the length of the 18AWG wire on the fixture, you can cut it down, but the voltage drop of a lead wire of 3.28ft (1m) is negligible.

To calculate voltage drop percentage, you’ll need to know the current draw of your fixture. If you do not know the current draw of your fixture, you can calculate it using the power and the voltage of the fixture. If you don’t know the power of your fixture, you can calculate it using the length of the fixture and the watts per foot.

Once you have your current draw, it’s much easier to use an online voltage drop calculator.

We’re using this calculator for this post, but GLLS does not endorse it. You can find many calculators online with a quick search!

Let’s go through an example.

We want to connect a 32.8ft (10m) single feed, 5700K, Vivid S fixture to a power supply sitting 20 feet away. First, let’s calculate the power.

To calculate P (power), we need the length of the fixture, and the power consumption of the fixture. Our length is 32.8ft and power consumption for 5700K Vivid S is 3.66W/ft.
voltage drop and wire gauge

With P, we can now calcualte current draw (I), which is measured in amps. To calculate I, we need the voltage of the correct power supply of the fixture and the Power we just calculated. For this fixture, the correct power supply is 24V.
voltage drop and wire gauge

Now that we know our current draw, we can move on to the online calculator.
voltage drop calculator
You can select from different types of wire, but ours are copper.

voltage drop calculator
Plug in the correct values for your fixture.
Make sure you’ve selected the correct current type, most of our fixtures use DC.
Current in amps is the value we calculated for I.

Click Calculate!

voltage drop calculator
From these calculations, we know that our voltage drop percentage is 5.31021%. This is well below the maximum 10%, so our fixture will be fine with an 18AWG wire.

What if my percentage is over 10%?

Say we needed a 40ft wire to connect our power supply to our fixture.
voltage drop calculator
We can no longer safely use an 18AWG wire since our percentage has gone over 10%.
The simplest fix for this situation is to use a thicker gauge wire. Let’s try it with 16AWG:
voltage drop calculator
Using a 16AWG wire, our percentage has dropped significantly and it’s now safe to connect our fixture to power.

Check back in for our next Tech Talk; we’ll be covering how to choose the right controller for your project!

Have any technical questions? Contact Tech Support!

Want to suggest topics for future posts? Let us know!

To speak with a sales rep about our LED Neon Flex products, Contact us today!

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