Choosing Wire for Your DIY LED Light

Due to the low-current nature of most LED light systems, most of the wire you find lying around should do the job. There are, however, a few considerations you should make to ensure what you’ve got will fit the bill.

Solid Core vs. Stranded Wire

Wire comes in a couple flavors: solid core and stranded. Solid core wire consists of a single solid conductor (usually copper), wrapped by a plastic insulating jacket. Stranded wire contains a number of individual conductors in a bundle which is then wrapped in an insulating jacket.

In the past, I’ve recommended stranded cable for this application, but have changed my mind over the past few months. While stranded is much more flexible, it’s also more difficult to work with and sometimes requires a little bit of solder to stiffen it up enough to jam in a connector. For this reason, I’ve since changed my recommendation to solid core wire for LED applications. It’s definitely flexible enough to do the job and it’s much easier to make connections with.

Stranded vs. Solid Wire for LED COBs

Selecting Proper Gauge

It’s important to select the right gauge of wire for your system. Bigger wire is nearly always better (the main problem with big wire is its flexibility and difficulty of termination) but most LED grow lights don’t draw a whole lot of current and will not require large wires. When it comes to choosing wire, you’ll see that the wire has an AWG (American Wire Gauge) designation. AWG ratings for wire work in a funny way – the larger the number, the smaller the wire. For example, the diameter of a 16-gauge wire is physically larger than that of an 18-gauge wire.

There are 2 things to consider when selecting the size of wire for your system: voltage drop and ampacity of the wire.

Voltage Drop

Although it’s an excellent conductor, copper does have inherent resistance. The longer your run of cable, the more resistance (measured in ohms) you’re going to see on your circuit – just due to the cable itself. Also, as your wire gets smaller, resistance increases, since there is a smaller area for electrons to flow through. So why does this matter? Well, due to Ohm’s law, as resistance increases, voltage will decrease. If your wire is too small and the run too long, you may find that the 36V your driver is putting out is actually only 35V by the time it’s traveled the length of the wire. This voltage drop could cause problems in a constant voltage system where small changes in voltage can produce large changes in current.

Try punching in a few numbers on an online voltage drop calculator to see what type of voltage drop you can expect with varying currents, wire sizes, and run lengths.

Wire Ampacity

Most importantly, you’ll need to make sure the wire you choose is large enough to handle the current you’re sending through it. If your wire is too small, it can heat up due to resistance, and this can be dangerous. If the wire heats up too much, you can melt the jacket on the wire, and, in the worst case scenario, start a fire. Another spec to take into consideration is the voltage rating of your wire. Often, smaller wire is rated for 300V, so don’t exceed this on your circuit. Usually, the connectors in the circuit are rated for less than this – most are 250V – so it’s a good idea to keep the voltage low anyway.

Realistically, since the majority of DIY LED setups have relatively short wire runs and are connected in series with a low amount of current flowing through each chip or board (often 700mA – 3A at most), you can get away with some very small wire. However, if you happen to be driving a large number of lights hard in parallel, you could end up with enough current to make you think twice about the wire you use. Have a look at the chart below for the current handling ability of different wire gauges (the numbers are pulled from the Wikipedia entry on American Wire Gauge).

Size Ampacity (A)
12  gauge 30
14 gauge 25
16 gauge 18
18 gauge 16
20 gauge 11
22 gauge 7
24 gauge 3.5
26 gauge 2.2

Summary

Now, I personally use a solid core 18 gauge wire for all my lights and would recommend you do the same. The cost difference between it and smaller cable is essentially negligible, and 18 gauge is about as big as you can go if you still want to be able to fit it into most COB holders or terminals. A larger cable like this reduces voltage drop and don’t have to worry too much about overloading it (unless you’re running a crazy amount of power on a single cable) since it’s capable of handling much more than the average COB system will be using.

14 Comments

  1. noel

    So I’m assuming you don’t tin stranded wire before you push it into the holder?

    • LEDGardener

      Oh you certainly could but I figured it’d be worth mentioning since I’m thinking the majority of people that get solderless holders don’t want to do (or can’t do) any soldering at all.

  2. noel

    I was going to just solder right to the chip due to the citizens have screw holes, but for less than 20 bucks I got the holders instead. I figure the holders give the chip more even pressure down on the heatsink.

    • LEDGardener

      Yeah you’re probably right. I just had a look at the instruction manual for mounting those COBs and I’d definitely go with holders too.

  3. Darren Bradley

    I’m looking to build a LED strip About 100 metres with a series of leds as a project for Christmas next year. Just wondering if you can advise me on what I would need and some options on powering it. Battery or electricity

    I have 1000 multi coloured lights, would I need more?
    What type wire is best
    Are there different leds that would suit this project as it’s an outdoor arrangement.

    Any advice would be appreciated.

    Regards.
    Darren.

  4. Matt

    Just a heads up to anyone building lights, thermostat wire is usually 18g solid core wire and is usually available by the foot in 2,3,4,5 wire configurations. It’s usually easier to find than a spool of wire labeled 18g solid core.

    • Mike D

      Be careful with that thermostat wire. Every spool I’ve seen is rated 150V or less and 60°C. This is not what you want. Be sure your wires are rated at 300V (600V should be easy enough to find) and at least 90°C (105°C would be better).

      • Reggie

        Why? Most people are only running 12v-24v.

        • Bob

          Not really up on LED lights for trailers but I think you definitely have a point! The LED lights run off 12V DC on cars and pickups supplied to the light you are installing by the vehicle….

          Most household light fixtures use drivers for LED fixtures . The power to these fixtures is normal 120V AC. If you mess with the wiring inside the fixture you need to be careful what you change – contact manufacturer about internal wiring voltage ratings!

  5. Dave

    I know this is an older post but hope you can answer a couple questions about a build. I am adding two, 2’ Samsung F564B’s to an existing 2’ – 4x Photo Boost strip light. I’m running the F564B’s and PBS’s on separate channels with HLG-120H-C1400B drivers for each channel. Can I use a single 4 strand, 16AWG cable to power both channels? I plan to mount the drivers, rocker switches and potentiometers remotely approx 15’ away from the light. Also I am considering adding a single 2’, T-5 UV fixture to the light, could I run all three channels on a single six strand cable? Thanks! – Dave

  6. Anonymous

    Thermostat wire is not rated for the loads of leds it is a control wire and a class 3 rating you need a class 2 wire rated for constant power.

  7. Scott

    Ummm if your applications have any movement or vibrations do NOT use solid core hookup wire. It will only be a matter of time before the wire breaks at the flex points.

  8. Dan

    Something in three sections of eight LED lights can I run 14 gauge up to them ?and then run 18 gauge between them?

  9. Anonymous

    Be careful with solid wire on a dc build. Note dc current runs on the outside of the wire, and ac current runs through the wire. Stranded wire is better for a dc build, because it allows mor current.

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