What size wire do I use for L E D nav lights?

I'm getting ready to close off the leading edge of my 2+2 wing and I installed a light weight conduit to later pull wire through for the nav and landing lights. I tried to figure out the wire size using AC43-13B but didn't make much sense out of it, sorry to say. The nav lights will be L E D so they will be very low current draw; about 1 watt each. Each wing will have one L E D landing light drawing 8.8 watts. I sure could use some help either figuring out how to use the chart in AC43-13 or an idea as to what size wire to use for the application. Each wing conduit will need to run the power wire for the nav light and a power wire for the landing light. I will need to run a ground wire also (wood wing); should I run a separate one to each light or one in each wing and branch off to each light? Thanks in advance; I'm out of my element as I start to think ahead to electrical.

Thanks,
Marty57

What you are really looking for is the voltage drop in the wire. Keep it less than .5 volts per the FAA
Search for a Voltage drop calculator
www.calculator.net/

I would use a separate wire for each ground, but that is just the way I do it. You could use a larger ground wire to carry the current back to the ground buss.

more info on wiring here
www.faa.gov/regulations_policies/handbooks_manuals/aircraft/amt_airframe_handbook/media/ama_Ch09.pdf

be sure to measure the distance from the CB to the load (light) and back to the ground buss for your distance

At a Minimum I would use 20 g for the Nav, and 18 g for the Landing

You don't have to guess; you don't have to calculate: all you have to do is read the instructions on whatever appliance you decide to install.

The LED manufacturers include that information in the box and also online.

Hello Marty did you ever build spoilers for your wings i have a complete set and the lever for the cockpit all brand new !!!

Marty, Aeroelectric.com may be helpful as you start this part of your project. I am sure you are a tool guy so I would suggest an Ideal Crimpmaster tool, dies are available for insulated and uninsulated terminals in the common sizes you will need and also BNC antenna connectors. Elecdirect.com is the cheapest I have found for ring terminals and splices, Made in the USA all tinned copper and use the nylon insulated, not pvc. They also discount Cole-Hersee solenoids and switches, much higher quality components than ACS IMO. I am sure your electrical work will turn out as pretty as your wood work, Jim

Jim,
Thanks for the links. I'm just starting to think this out but will be there before too long and need to be ready. So far all I have done is to mount a conduit inside the leading edge "D" in preparation to gluing on my leading edge skins. This way I can pull the wire latter as I'm ready. It looks like 22 gauge wire will work with the LED Nav lights and 18 gauge for the LED landing lights. I can pull those wires when ready. Lots to plan so thanks for the info and the kind words regarding my work. Here's the leading edge before I button it up.

Marty57

..... make that 20 gauge for Nav lights. No on to gluing on the leading edge and finishing up these wings.
Marty57

Marty, go ahead and fish some different colored strings through that flex conduit before you put the leading edge on. Maybe pull 4 tightly and secure to each end. That flex conduit is kinda hard to run wires through because of the ridges.

Marty57 said:

I'm getting ready to close off the leading edge of my 2+2 wing and I installed a light weight conduit to later pull wire through for the nav and landing lights. I tried to figure out the wire size using AC43-13B but didn't make much sense out of it, sorry to say. The nav lights will be L E D so they will be very low current draw; about 1 watt each. Each wing will have one L E D landing light drawing 8.8 watts. I sure could use some help either figuring out how to use the chart in AC43-13 or an idea as to what size wire to use for the application. Each wing conduit will need to run the power wire for the nav light and a power wire for the landing light. I will need to run a ground wire also (wood wing); should I run a separate one to each light or one in each wing and branch off to each light? Thanks in advance; I'm out of my element as I start to think ahead to electrical.

Thanks,
Marty57

Click to expand...

Hi Marty

Use the chart from the AC 43-13. But first calculate your current draw for each light.

Watts = volts X amps, so if we juggle the formula we can get amps by using watts/volts = amps [1/12=.08]. Looking at the chart (for continuous current flow) lets use the diagonal line for 1 amp and estimate 25 feet of wire. Use the 1 amp line as its the smallest amount of current shown on the chart and use the 25 foot length as a good estimate and it falls on a horizontal line. Now trace the 1 amp line down and trace the 25 foot line from left to right, until they intersect. In this case they intersect between the columns for 24 gauge and for 22 gauge, so round up to the 22 gauge. NEVER round down as this will result in a to small wire for the current flow.

Now to calculate the breaker size, add the total current flow for each of the three nav lights, 3 X .08 = .24 amps. Since the breaker is intended to protect the wire and not the components, we are safe in using a 1 amp breaker on the nav light system. Remember that we used 1 amp in our wire calculations. If any one wire shorts out, the breaker will open at 1 amp and the wire is large enough to handle that 1 amp and not be damaged.

Do the same for the landing lights. Watts/volts = amps [8.8/12 = .73]. Round this up to 1 amp for each light and double that as you have one light on each wing. Find the 2 amp diagonal line on the chart and trace it down until it intersects with the 25 foot horizontal line. In this case it falls right on the 20 gauge column. If we install a two amp breaker, we will have enough power to operate the landing lights and have protection for each individual wire. I know that some of you are saying 'surge current' and 'derating factor' right now. Experience has shown me that LEDs have a very even current flow and not much of a surge current on start up, so these are safe calculations.

Just some tips from my experience:
Use single conductor, shielded wire, so you can run power on the center conductor and use the outer shield for your ground path. I do this on wings with a metal spar, too. Helps me avoid ground problems from paint and powder coating. Also is the best way to wire lights in rudders. It gives you a continuous ground path independent of the rudder hinges. No more blinking lights during taxi!

Avoid using wire smaller than 22 gauge for airframe systems. They require smaller than standard terminals and lack the mechanical strength to withstand vibration and abuse. These smaller terminals are expensive and require special tooling. Anyone telling you to do things like double the conductor to get it to crimp into standard size terminals is not your friend. Just remember me telling you that it's not good shop practice, it's unprofessional, and they're a hack.

You didn't do yourself many favors with the corrugated conduit. It's difficult to route wires through. I've never been a fan of using a conduit unless it has a special use to protect the wire from mechanical damage. Light wires are enclosed after installation, so I don't see the need. Since the wing is still fairly open, why not route the wires now?

If you do much electrical work, study up on the charts in the AC 43-13. One is for continuous current flow and one is for intermittent flow. The continuous flow chart is the most useful. Start with the voltage of your circuit and you can calculate wire size, wire length, current capacity for a specific size of wire, and correct breaker size.

Let me know if I can help you out.

Web

Web,
I ran the ribbed conduit with the idea that I could latter pull the wires as needed; maybe I don't need it at all? I have a spool of 22 gauge wire on hand and I have three strings inside the conduit. I'll try pulling some wire through the conduit before I start closing off the leading edge and see how it pulls. If necessary, I could just tie the wire to the wood rings I am running the conduit through. I attached a picture of the rings so you can see what I have. Thanks for the info; this is all so helpful in understanding where I need to be going before I close up the wing.
Marty57

Marty57 said:

Web,
I ran the ribbed conduit with the idea that I could latter pull the wires as needed; maybe I don't need it at all? I have a spool of 22 gauge wire on hand and I have three strings inside the conduit. I'll try pulling some wire through the conduit before I start closing off the leading edge and see how it pulls. If necessary, I could just tie the wire to the wood rings I am running the conduit through. I attached a picture of the rings so you can see what I have. Thanks for the info; this is all so helpful in understanding where I need to be going before I close up the wing.
Marty57

View attachment 16904

Click to expand...

I would just route the wire through the existing structure. If you are worried about chafing, take a short piece of plastic tubing and glue a piece inside of each of your wooden rings. Then route your wires through them and secure them. If you do stay with the conduit, try pushing the wires through with a fiberglass rod. I have a kit with sections of these rods that screw together. Very handy.

Don't forget that you will need a power and a ground path for each light. That's one reason I use the single conductor, shielded wire on these lights. Ground the lights back to your airframe ground and don't try to daisy chain all the grounds to one wire inside the wing.

Web