18/2 Low-Voltage LED Wire, Red and Black, Pure Copper, 50 or 100 ft

This is the wire for the low-voltage side of an LED sign. It is 18 AWG with two conductors side by side, often written 18/2: red for positive (+) and black for negative (-). Each conductor is stranded pure copper, so it bends easily around corners inside letters and raceways and holds up when you work it into place.

Use it for:

• The run from the 12 V power supply to the first letter.
• Jumpers from letter to letter.
• Re-wiring a letter or a lightbox after a repair.

It comes in 50 ft and 100 ft lengths.

It is not for line voltage. The 120 V wiring that feeds the power supply is done by an electrician with wire rated for that job.

Keep the polarity straight: red to + on the power supply and on the LEDs, black to -. LEDs connected backward usually just stay dark, so if a letter does not light after you wire it, check the polarity first.

On long 12 V runs, voltage drop matters. Current flows out on one conductor and back on the other, so the copper the current travels through is twice the run length. 18 AWG copper has a resistance of roughly 6.4 to 6.7 ohms per 1,000 ft. Example: a sign drawing 3 A at the end of a 20 ft run passes through 40 ft of copper, about 0.26 ohms, and loses about 0.8 V. The far letters then look dimmer than the near ones. To fix it, move the power supply closer, feed long runs from both ends, or split the letters across two runs.

Where the wire passes through a wall or ceiling, ask your electrician which cable type your local code calls for; many inspectors expect cable marked CL2 or CL3 inside walls. Outdoors, run the wire inside the letters, the raceway or conduit, and seal every connection.

Measure the path the wire will actually take, not the straight line: from the power supply, along or through the wall, into the first letter, then from letter to letter. Add a few feet at each end for connections and mistakes. Under about 40 ft in total, the 50 ft spool is enough; beyond that, take 100 ft.

Then check the load. If the run is long and the sign draws several amps, work out the voltage drop with the method above. When the loss is large enough to dim the far letters, shorten the run by moving the power supply, feed the run from both ends, or split the sign across two runs.

If any part of the run goes inside a wall, ask your electrician about the cable type before you buy.