In the U.S., wires are sized by the AWG (American Wire Gauge) system. The higher the AWG number, the smaller the wire diameter. 

What you need to know ahead of time:

• Your vessel’s system voltage - typically 12V or 24V.
• The total current draw of the number of lights you are planning to power on the circuit. This will depend on system voltage (current draw information can be found on the product packaging or on the Lumitec website). If powering multiple lights, add up the current draw per light rated for your system voltage.
• Distance of wire run (from the power source to the light AND BACK).
• Your voltage drop requirement (Lumitec always recommends using 3%)  – Voltage drop is the change in voltage along the wire due to resistance in the wire.

Here’s a simple equation to keep in mind:

(Distance from Battery to Light x 2 = Total Wire Run)

Determine the correct wire gauge by using one of several tools:

• Wire Gauge Table Charts
• An Online Calculator
• ABYC Wire Sizer App

Some things to be aware of:

• ABYC requires a minimum of 16AWG on most single-conductor wire runs. So, even if the table or calculator says 18AWG, you should use 16AWG if running a single wire.
• A boat’s battery doesn’t always produce 12V and can run as low as 10V under certain operating conditions or up to 14V when charging. This changes the current drawn by the lights and can sometimes require selecting a larger wire size. A good rule of thumb is to use the next heavier gauge when possible.
• When Planning the Wire Run:
  •  Do not run in parallel in the same bundle or conduit as low-voltage signal cables such as audio input wires. This helps avoid picking up noise in your audio system.
  • Use a common ground near the battery, and DO NOT connect to a long shared ground line that boats sometimes have. Otherwise, this can add noise to speaker systems.
  •  The audio system and lighting system incoming power should not share the same terminal blocks to help prevent a buzzing sound on the speakers.
  •  Avoid making right-angle turns on sharp edges, as this will eventually cut through the wire insulation. Use grommets where necessary.
  • As a best practice group, the positive and negative (red/black) wires together and avoid separating them as much as possible throughout the run.
• In the Marine industry, you MUST use adhesive-lined butt connectors to prevent moisture from ruining the connection. Any exposed metal of the wire is a point where moisture can travel along the wire and get into the electronic components at the end of the wire.
   

Information was referenced from ABYC E-11: AC & DC Electrical Systems on Boats.

Download Wire Gauge Charts >

 High current in DC electrical systems can cause electrical components to overheat and possibly cause a fire. A fuse is an electronic safety measure that provides overcurrent protection to an electrical circuit. It is usually a metal wire or strip precisely sized to melt when too much current flows through it. When sizing a fuse, it is important not to undersize or oversize it. 

Simple Rule of Thumb Equation:

Minimum Fuse Size = Light Amp Draw at System Voltage x Number of Lights x Safety Factor of 1.4 (Round Up to Nearest Fuse Size)

When Selecting a Fuse:

• Determine the ampacity (current-carrying capacity) of the smallest wire on the circuit. You can use the table below, which lists allowable amperage for conductors based on AWG size, temperature rating, and whether inside or outside of an engine space.
• Determine the maximum continuous current that will flow through the circuit. It is best to assume voltage drop and battery fluctuation will cause the voltage to be below the rated system voltage, so Lumitec recommends using a voltage value of 10V for 12-volt systems and 20V for 24-volt systems (For safety, we recommend keeping the maximum continuous current of circuits with LED lights under 10 amps).
• Check the Ampere Interrupting Capacity  (AIC) tables to find the minimum AIC acceptable for the circuit.
• Select a fuse that has an amp rating lower than the ampacity of the smallest wire, higher than the maximum continuous current, and meets the minimum AIC rating.
• If you can’t find an exact match, ABYC allows for a fuse one size higher than the ampacity of the smallest wire on non-motor loads such as LED lights, as long as the fuse rating does not exceed 150% of the ampacity.

When Choosing a Fuse Location:

• Place the fuse on the positive side of the circuit at the power source or as close to the power source as possible - depending on the circuit layout, the power source can be the battery, the battery switch, the distribution panel, a subsidiary panel, some distribution bus bar, or another connecting point.
• If using a power source other than directly to the battery, and the wire coming from the power source is sheathed or enclosed, ABYC allows for the fuse to be up to 40 inches down the wire, but no more. And if the wire is not enclosed or coming directly from the battery, the fuse should be within the first 7 inches of the wire.

What You Will Need to Know:

• System Voltage (12VDC or 24VDC).
• Current Draw at system voltage (amps) for each light on the circuit (you can find this on the light product pages).
• Total Load on the circuit (individual light amp draw times the number of lights on the circuit).
• Voltage Drop (we recommend 10V for 12-volt systems and 20V for 24-volt systems).
• Safety Factor Buffer (we recommend between 1-1.4).

Useful Formulas:

• Total Power Draw = Power Draw from each load source combined.
• Factor of Safety = Fuse Rating / Maximum Current (account for voltage drop and battery voltage fluctuation). We recommend a safety factor of 1.1 to 1.4.

Download Amperage Chart >

Wiring recommendations: Use ABYC standards to calculate wire size based on the length of the run. 

TIP: To minimize electrical noise and interference, running the positive (red) power and ground (black) return together for as much of the wire run as possible, ideally inside a jacketed cable, is recommended. Avoid loops and coils of the wiring.

Wiring recommendations: Use ABYC standards to calculate wire size based on the length of the run. If installed as a 3-Wire configuration, the orange wire carries less than 1A of power, and typically, an 18AWG wire can be used. The orange wire of the light is the internal relay and is also the wire that sends commands from Poco.

TIP: To minimize electrical noise and interference, running the positive (red) power and ground (black) return together for as much of the wire run as possible, ideally inside a jacketed cable, is recommended. Avoid loops and coils of the wiring.

• Ensure that the circuit you are connecting to has no power. You should turn off your house battery and test to ensure the circuit is not energized by using a multimeter before continuing.
• Run a marine-grade 3-conductor wire from the light to your switch and power source. The red wire will connect to constant power after the house power kill switch, the black to common ground, and the orange wire to the normally open side of a switch. You should install a 7.5A fuse on the red wire on a 12vDC system (3A @ 24vDC).  View wire gauge reference chart HERE.
• Connect the wires from the light to the new wire run and follow ABYC standards. Ensure that the wires are crimped correctly, and use a heat gun on the heat shrink of the butt splice connectors. 
• Turn on house power and test the new underwater light.
• We recommend that each light is on a dedicated circuit with a maximum of a 7.5A fuse