Electrical wire size ??

[Chaz]

Just a quicky question:
  Can I use 14 AWG cord (lamp cord) for my 24 volt lighting? (rope and single fixtures)

  Thanx,
     Chaz

[H3Jim]

Propbably, but how much current do you intend to run through it?

Keep in mind that many RV fires are from the low voltage side, not the 120 volt side. 

I would be concerned about the quality and thickness of the insualtion.

[skipn]

Chaz,

   My gut instinct was a probably depending on length and amps so I did some research.

 Quote from one of the engineering calc sites.
"In an electrical systems the conductors should not be sized with voltage drops exceeding 3%."

  Using a calculator from http://www.csgnetwork.com/voltagedropcalc.html
   for 24V dc 14 awg
   I came up with 20 feet @5 amp draw  2.5%drop
  Play around with the calculator

   YLMV    L=length

     Skip

[JackConrad]

Chaz,
   When we wired our bus, we used a minimum of 12 gauge wire.  Better safe than sorry. Also use fuses or circuit breakers of the appropriate amp rating to match the wire size.  Jack

[Chaz]

Thanx guys. Good info! I'm insulating and want to wire some stuff while I'm at it. I tend to overkill allot.    I'd much rather be safe that sorry.
 
I'll work with that calc, Skip. I guess I should decide which lights i will be using to be able to figure out the final figure. But I am dead set on using 100% LEDS on all the 24v stuff. I think that will help some.  Won't it?

Thanx again,
    Chaz

[skipn]

 Chaz,

    It's all a numbers game............ # of lights and their draw.

   Generally
         LED least draw
         Fluorescent (IF they are not being turned on and off every 2 mins!) ARGGGGGGGGG
         Condecent easiest to find but biggest draw

 Skip
       

[belfert]

I would not use lamp cord even though it is cheap.  It is not intended to be covered.  I have also seen old lamp cord with lots of cracks.

I did like Jack and used a minimum of 12 gauge no matter what amperage.  I used 10 gauge for a few circuits like the 12 volt jacks and lights in the bunks where I thought power draw could be high.

I used tinned marine wire that is UL listed mostly from skycraftsurplus.com.  If you don't see the right AWG and color on the web site call them as they have more not listed online.

[Rick Brown]

A most useful resource is the "Pocket Ref" by T.J. Glover.  A compact little black book of more than 500 pages.  I got mine at a hardware store.  A table of "Standard Lamp & Extension Cord Current Capacities" says 14 gauge cord is good for 18 amps should be protected by a 15 amp breaker.  The voltage rating of a wire specifies the maximum safe voltage.  Anything less than that makes no difference.  The book also says 1000 feet of 14ga presents a resistance of 2.58 Ohms from which you can calculate the voltage drops.  Keep in mind that when most things (lights, fans, radios, etc.) call for 12 or 24 volts that means 'about' and +/- 20% is a safe operating range.
-RickBrown in Reno NV

[Don4107]

"I would not use lamp cord even though it is cheap.  It is not intended to be covered.  I have also seen old lamp cord with lots of cracks."

I have seen some not so old lamp cord falling apart too.  Last thing I would use.  I strongly agree with Brian.

Don 4107

[Nick Badame Refrig/ACC]

Hi Chaz,

This link is available in "The Green Book" thread under Board Help Section on the front page.

It's a very easy table/chart for 12v dc wire sizing

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

Nick-

[Chaz]

Hey, thanx guys!!! I'll take your recommendations and run with it!!

  Chaz

[boogiethecat]

Not to hijack the thread and not directly on the subject, but while we're on "wire" I thought I'd post this photo of a little test I did a few years back for the BNO folks, regarding the use of solid vs stranded wire.
  I did a very informal test, took various wire styles and clamped them in my mill vise and a drill chuck, and bent them up and down all the same distance etc, until they failed.  Quite interesting, and to me says "For busses and where wire gets wiggled alot, use stranded, and the finer the strands the better".  Of course those in the electronics industry already know this, but the bus folks seem to argue it over and over and over. 
 The picture says a thousand words...

[Dreamscape]

No arguement from me!

Great test.

I have always used stranded in everything but a house. It takes a lot more abuse, vibration etc. Really, it is just logical if you think about it. Also securing it ends up with a better result for the long term. Still need to check the terminal connections at least once a year, make sure they are good and tight. Gotta keep the smoke in.

Thanks for sharing that.

Paul

[Blacksheep]

Not to dispute anything everyone has said but there is a stranded wire that looks like lamp cord but isn't. It's actually used fro outdoor lighting like around gardens and sidewalks. To me, it looks like lamp cord but I think it is better than that! I have used it for my 12 volt water pump and it hasn't failed me yet and doesn't show any signs of failure either.
Just another consideration other than lamp cord!

BS

[Stan]

When I bought Noma outdoor lights, the wire that looked like lamp cord had quite a thick insulation but was low voltage wire (not for 120 vac).