Date: Wed, 10 Jan 2018 17:39:18 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Multi Conductor Shielded Automotive Wire Temperature Rating
In-Reply-To: <CAB2RwfjhJhTXtpv2cByzuCscwr5CcLC=u6vWoLSYxeq3atXRyw@mail.gmail.com>
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Changing the length of a ground wire isn't likely to make much difference
unless it's carrying noticeable current, in which case if you double the
length as a rule of thumb you should go down three AWG numbers (or double
the number if you're using mm^2 wire).
Changing the *location* of a ground won't generally be an issue for power
wiring but could be for signal wiring. Generally speaking "ground"
currents in the chassis will follow the shortest straight path to the
battery ground cable. Running grounds belonging to one system to multiple
places can introduce a problem called a ground loop. In an extreme case I
have seen a printer cable melt because the printer was plugged into a
different circuit than the computer (they were six feet apart on a factory
floor, but different circuits).
All wire/grounding considerations become more stringent or difficult as you
move away from DC. The higher the frequency the worse the problem.
http://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
Yrs,
d
On Wed, Jan 10, 2018 at 5:12 PM, Neil N <musomuso@gmail.com> wrote:
> Thank you for those links.
>
> At my skill level, the electrical details I consider are beyond me in most
> ways and from one point of view, I'm really "splitting hairs" here when I
> probably don't need to. Distinctions between how Bentley labels a given
> ground point, i.e. where it's located, wire length to it, and whether or
> not adding or subtracting wire length to a given ground path matters, may
> not. I guess what I'm trying to say is that from the layman POV for most
> people doing a swap, running all the engine management grounds to one or
> two locations shouldn't be a problem. Ironically, on my currently running
> swap, one "sensor" ground wire is shortened by 90% and AFAIK, the sensors
> work fine. (yes I corrected a long standing mistake!) And, swappers end up
> cutting up (shortening) the harness as it is anyways. e.g. wires to/from
> the TPS. But as I say, "At my skill level... "
>
> ;)
>
> Knowing a little more now on this second harness, i can see that ground
> locations, wire length, likely has more to do with the design of the
> vehicle and component location rather than millivolt considerations. .....
> I think.
>
> Neil.
>
>
> On Wed, Jan 10, 2018 at 12:48 PM, Steve Williams <sbw@sbw.org> wrote:
>
> >
> >
>
>
>
> > Right. In my Vanagon I installed a ground farm from B&C under the
> > driver's seat:
> >
> > http://www.bandc.aero/grounding-supplies-battery-cables.aspx
> >
> > The big camping battery is inside the sink cabinet, a few inches away
> > since I drilled a big hole for the heavy + and - cables. The battery -
> > cable is connected right to the big bolt on the ground farm.
> >
> > In homebuilt aircraft, that bolt is intended to go through the firewall
> to
> > a ground farm on both sides of the firewall, so there's one ground point
> > for absolutely everything. I didn't drill through the van's floor, but
> > instead grounded the ground farm to the van's body through a separate
> short
> > wire.
> >
>
>
>
>
> --
> Neil n
>
> Blog: Vanagons, Westfalia, general <http://tubaneil.blogspot.ca>
>
> 1988 Westy Images <https://picasaweb.google.com/musomuso/New1988Westy>
>
> 1981 Westfalia "Jaco" Images, technical <http://tubaneil.googlepages.com/>
>
> Vanagon-Bus VAG Gas Engine Swap Group <http://tinyurl.com/khalbay>
>
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