[PSUBS-MAILIST] Earth Fault

[James Frankland via Personal_Submersibles]

ok, that makes sense.  It must be conducting.  In fact i'll test it later.

On 27 July 2015 at 13:27, hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

>
> James,
> I have had this problem with rubber washers.  Some rubber contains carbon,
> I always put an ohm meter on material that needs to be an insulator.  Your
> rubber is likely a conductor.
> Hank--------------------------------------------
> On Mon, 7/27/15, James Frankland via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>  Subject: Re: [PSUBS-MAILIST] Earth Fault
>  To: "Personal Submersibles General Discussion" <
> personal_submersibles at psubs.org>
>  Received: Monday, July 27, 2015, 6:13 AM
>
>  No.  Just
>  sat on the trailer.
>  On 27 July 2015 at 11:58,
>  Alan via Personal_Submersibles <personal_submersibles at psubs.org>
>  wrote:
>  James
>  were they in the water?
>
>
>
>  Sent from my iPad
>
>
>
>  > On 27/07/2015, at 10:33 pm, James Frankland via
>  Personal_Submersibles <personal_submersibles at psubs.org>
>  wrote:
>
>  >
>
>  > Hi All
>
>  >
>
>  > I have a very peculiar issue.  I have an earth fault
>  on the boat.
>
>  >
>
>  > My test consists of holding one probe of the meter on
>  the positive battery terminal and the other to the hull
>  somewhere.  I was showing a reading of 24v.  So obviously
>  a negative connection somewhere to the hull.
>
>  >
>
>  > I went around everything taking things off and have
>  tracked the fault down to the lights.
>
>  >
>
>  > The lights are the trustfire ones and the negative
>  connection is grounded to the chassis of the light.
>  However, when I fitted the lights, I was aware of this and
>  so insulated the mounting bracket from the  light casing
>  itself with a piece of rubber.  So theoretically, there is
>  no physical connection from the case to the hull.  Only the
>  internal wire.
>
>  >
>
>  > Anyway, if I disconnect the lights and leave them
>  dangling on their wires, there is no earth fault.  The
>  lights all work, and the hull is clean of current.
>
>  >
>
>  > So the lights must be leaking back through the
>  connection somehow, but I cant see how.  The case is
>  insulated from the mounting bracket with rubber and the
>  brackets are connected to the fibreglass faring, so it
>  shouldn't leak back?
>
>  >
>
>  > Anyway, ive fixed it by insulating the mounting bolts
>  with delrin washers, but I cant see how the earth could
>  return through a piece of rubber and then glass fibre.  A
>  mystery unless anyone can see something obvious?
>
>  >
>
>  > Regards
>
>  > James
>
>  >
>
>  >
>
>  >
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