Date: Mon, 31 Aug 2009 12:53:51 -0700
Reply-To: neil N <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: neil N <musomuso@GMAIL.COM>
Subject: Re: Wire size question.
In-Reply-To: <6bc66ccf0908311127i4db275a2n263a84a6d83e2da0@mail.gmail.com>
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On Mon, Aug 31, 2009 at 11:27 AM, Don H
anson<dhanson928@gmail.com> wrote:
......
> The light came with a short supply wire that is
> quite small gauge...Maybe #8...Which seems small to me,
....
> So, I am planning on taking a wire from my Aux battery (under the drivers
> seat) fuse block (inside the undersink cabinet) up to the spotlight. I
> would like to be correct with the wiring. The run will be about 6-8' from
> the fuse block up to the pigtail that comes right out of the light. I plan
> on crimping the supply line with a butt splice. My question(s) are: What
> size wire should I run up to the light and won't that small wire pigtail
> that came on the Unity spotlight get hot if I use it? When you take a big
> wire for a long run then hook into a short smaller wire does the small wire
> become the hot spot in the whole run? Not sure I am asking this right, but
> it's the best I can do with the electrical knowledge I have..
> thanks, Don Hanson
Hi Don.
AFAIK, one should run the same size wire all the way to/from a given
appliance. If the spot light was originally designed to work with
wires running 6-8' from the power source, (this means length of all
wires used for the entire circuit) then adding wires that are the same
as stock wires on light, should be fine.
If crimping connectors to larger than #10 wire, (i.e. #8) you will
likely need a different crimping tool (the 2 crimp tools I have only
go up to #10) I bought an offshore offering for this. Works fine.
#8 wire, depending on length etc., (entire circuit) #8 can handle
quite a few amps. i.e. it's not a small wire. :)
There are online wiring charts that show how many amps a given gauge
of wire can handle. BUT, this depends on length of runs (round trip),
environment (heat) etc.
If I need to get a rough idea of what gauge wire I'm dealing with, if
I have ample wire to "play with", I eyeball it and strip off a bit of
the casing. If wire stripper strips a few strands out, I increase size
til no strands come out. There are more accurate ways to tell though.
If you set your VOM right, (to measure current) you should be able to
put it in the circuit, turn on light, and see how much current it
draws. This will tell you what wire/parts to use. (like are you
installing a switch?)
If it draws a LOT of current, the stock fuse holder may not be
sufficient. And, you might need a relay to handle this.
Of course I can't attest to the accuracy, but here's some links to
wire gauge/amps.
This one shows #8 good to 150 amps:
http://www.rowand.net/Shop/Tech/WireCapacityChart.htm
This chart shows how ampicity of a wire decreases as length increases
http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm
It shows #8 wire is good up to 150 amps BUT that's up to max. 10' run
(round trip)
Neil.
--
Neil Nicholson '81 VanaJetta 2.0 "Jaco"
http://tubaneil.googlepages.com/
http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines
