The maximum run length for linear lighting products (such as rope lights, tape lights, and flexible neon) varies depending on the wattage and voltage of the light as well as the amperage of the power source.
Wattage and voltage specifications can be found on our website product pages, as well as on the product packaging and/or cut sheets. Amperage can be found printed on either the rectifier (power cord) or the DC power source.
Formula (Ohmís Law)
The basic formula to follow to calculate the allowable maximum run is based on the principle of Ohmís Law.
This formula provides the maximum theoretical limit.*
|Source Amps x Voltage
| = Maximum Run Length
Watts Per Foot
Example: Line Voltage Lighting
Line voltage products, such as 120 volt LED rope lights, allow you to plug the rope light directly to a standard 120V AC outlet. To do this, the power cord is fitted with a rectifier to change the AC power from the outlet to DC power that the LEDs can use. The amperage rating of this rectifier is important in determining the max length. Common ratings are 1.2A or 1.6A. Inputting the values from our 120v Directional Cool White Rope Light
as an example yields the following calculation:
|1.6A x 120V
| = 192 ft. Max Run
1.0W per foot
In this example, the manufacturer has a recommended limit of 150 feet, so while the numbers may calculate a higher limit, we need to stick to the manufacturer's recommendations and stay at or below 150 feet.
Example: Low Voltage Lighting
Low voltage linear lighting typically does not come with a rectifier, but instead requires a separate transformer or LED driver to power the lights. Use the amperage rating of the transformer to plug into the calculation. So let's take a look at some 24V low voltage neon and a 60W 24V dimmable driver:
But wait, how do we know the amperage of the driver? Many times the manufacturer specifications will note the max amperage of the driver or transformer. But if it doesn't, there's a quick calculation you can use to find the amperage. Watts, sometimes referred to as volt-amps (vA), is simply Volts * Amps. So spinning that around a bit, we get this:
|Wattage of Transformer
| = Amps
Output Voltage of Transformer
So let's input the values from our 24V 60-watt driver:
| = 2.5 Amps
Now that we know the driver has a maximum rating of 2.5 amps at full load, let's go back to finding our maximum length for the 24V neon:
|2.5A x 24V
| = 21.4 ft. Max Run
2.8W per foot
So this tells us that we cannot run over 21 feet of neon using this 60 watt driver. If you need to run longer lengths of light (up to the manufacturer's recommended maximum), then a larger capacity driver must be used.DO NOT EXCEED THE LOAD CAPACITY OF A TRANSFORMER/DRIVER - ALWAYS REFER TO MANUFACTURER SPECIFICATIONS*Some manufacturers will specify a max length less than the theoretical limit to ensure safe operation of their product. Always follow the manufacturerís recommendations.