Determining wire size

[Chappyd]

I'm finishing up the wings and looking for info on figuring out what wire to use for lights, auto pilot, ect. I have the big book, what is it, AC - something( not in front of me at the moment). I'm looking for info in a more readable form to learn about wiring and determining sizes.

Thanks,

[61Flyguy]

You start by determining what the current draw of the load is. From there you will select the wire gauge which can safely handle that load without dropping the voltage to an unacceptable level. The smaller the diameter the wire (higher gauge number) the greater the resistance and therfore the greater the voltage drop across the wire and less to the load. Here is a table showing max current for a given wire gauge along with some other info:

http://www.creativair.com/source/_inst/wiresize.pdf

[Mike S]

First, try searching the electrical system forum, lots of prior info there

Also, a couple of vendors websites have good info available in them.

http://www.verticalpower.com/documents.html

http://www.gen-aircraft-hardware.com/store.asp

click on electrical, wire/cable/tech info

[DGlaeser]

Bob's AeroElectric Connection book explains all about wire selection and LOTS of other stuff. If you ever have questions, the AeroElectric Matronics list is a great resource as well.

[Andy Hill]

You start by determining what the current draw of the load is. From there you will select the wire gauge which can safely handle that load without dropping the voltage to an unacceptable level.

Sorry - disagree

1. Determine Max Load required by 'applicance'
2. Protect that circuit by selecting CB/Fuse above the applicance Max (surge) requriement
3. Now pick wiring size according to CB/Fuse i.e. wiring will comfortably handle the max current the CB/Fuse will supply
4. Agree that if all the above complied with, and voltage drop excessive, move up a wire size - but this is not usual

NB the "crucial match" is CB/Fuse v wire, not appliance. Applicance / Fuse / CB failures are easily dealt with, and safe. Wiring failures are not

[Chappyd]

Thanks for the replies guys........gives me a place to start. I guess I can't put wire in until I determine what it will be running to. Going to have landing lights in both wings, with nav lights, and a TruTrak AP in the right wing. Meantime, I'll put a bunch of strings in the conduit.

So; Determine max draw-amps (?) of the appliance
CB to match max draw
Wire size more than adequate for the max draw, so the breaker will pop well before any damage could occur to the wire. So begins another facet of my education

I did try a search........I guess I didn't get the wording right, didn't find what I was looking for. Most of the time I do though

[FredMagare]

I sat down one day "many moons ago" and sketched out my wiring diagram according to the guidelines in the AeroConnection (great resource). Then set about ordering many different feet of 22AWG, 20AWG, 18AWG, 16AWG, 14AWG, etc. In retrospect what I should have done is consolidated my wire sizes! All of my 18, 20, and 22AWG requirements could be handled by 18AWG. All of my 16, 14, and 12AWG requirements could be handled by 12AWG. (And so forth.) You should still find the wire size requirements so you don't inadvertently use a wire diameter too small! But I don't think the weight penalty for upsizing wires in your aircraft (for the amount of wires we run) will have a measurable impact. Purchase wire in larger spools - you'll likely be able to save a few bucks. (Well, isn't that nice? )

[ScottSchmidt]

"If in doubt make it stout out of things you know about."

Good Luck

[az_gila]

Originally Posted by FredMagare

...... In retrospect what I should have done is consolidated my wire sizes! All of my 18, 20, and 22AWG requirements could be handled by 18AWG. ...... Purchase wire in larger spools - you'll likely be able to save a few bucks. (Well, isn't that nice? )

It's also much easier to work with 18g or 20g wire than the small 22g wire... and at these sizes, the weigh difference really is negligible as mentioned above.

gil in Tucson - who doesn't use 22g wire.....

[N941WR]

I sized mine based on the example in the builder's manual. Ok, since I have LED position lights, those wires are over sized. There were only a few places I felt like it was necessary to verify the wire size used, one of those being the jumper I made for my main buss to span where my throttle quadrant was in the way. Otherwise, I used standard wire and CB sizes as recommended by Van's and the manufacture of the equipment I was installing.

One of our tech inspectors did the math and upsized all of the wires in his very nicely equipped Velocity RG by one size and found it only added something like an extra 1/2 pound total. He felt this was a small price to pay for the extra wire size.