I always thought that mag. wire shielding was grounded at both ends. Am I
wrong on this?
As regards double-ended grounding resulting in a potential for shorts, I'd
always been curious as to why Rotax required such heavy cables (18awg) for
the kill switch wires of a CD system with its tiny currents. Now perhaps
there is a reason; the 18g would be (intermittently) capable of taking the
full rated output of the Rotax alternator in the event of the short you
describe and without burn-out. Unless you have your battery behind the
panel too, where is a greater current going to be sourced from betwixt
panel and engine?
Duncan McFadyean
On Wednesday, February 20, 2002 7:46 AM, Nigel Charles
[SMTP:72016.3721@compuserve.com] wrote:
> Message text written by INTERNET:forum@europaclub.org.uk
> >My 914 manual sez ground the 'mag' wire shields at the engine end
> only.<
>
> Although both ends is advocated by Europa to ensure grounding there are
two
> good reasons to ground at one end only:
>
> 1. To reduce the risk of interference from ground loops.
> 2. Should another ground between the engine and panel fail if the mag
lead
> is grounded at both ends an electrical fire could start due to this wire
> trying to provide an earth return at much higher currents than it is
> designed for. This has actually happened at least once.
>
> Whilst grounding the mags is important for safety any failure would
> instantly show up at shutdown. Also with Rotax engines the rpm needed to
> start the engine is much in excess of that achieved by turning the prop
> slowly by hand so the danger is already minimised. With dual grounding no
> failure would show up anyway until the second connection fails.
>
> Nigel Charles
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