Re: 24V+ Isolated Ground Leak


John Clark
 

Hi Paul and Bill,
   Am I wrong in thinking that the voltage readings are correct?   Amperage through the bonding system would be a problem.  

My SM 37, has had varying anode lifetimes.  Marinas and shore power shorten life,  I am currently moored and have been working a job in St Thomas for a year and a half. Before that boat parked in Brunswick GA with no shore power.   Cumulative four days in marina in STT and 2018 zincs look good to me.  A few years ago we spent a good amount of time in Le Marin at the dock…zincs did not like that.

Another place to check is the rigging.  My friend on SM24 had a sudden outbreak of rust trails from the rigging mounts.  He had 24v on the rig from a worn cable.  I had a similar experience with a previous owner installed 24v outlet on the main mast that corroded.

Boats….always something.  


  

On Mon, Sep 6, 2021 at 3:57 PM CW Bill Rouse <brouse@...> wrote:

Paul,

There is a 24-volt wiring bus behind the wood panel directly above the nav tabletop labeled 24-volt Permanent. This is hot when the switches are off. The only thing connected to that bus should be the 24-12v step-down transformer that powers the chain counter, the AM/FM Radio, and the 24v plugs at the nav station.

Locate this wiring bus. Is there anything connected to it other than the step-down transformer?

Sorry I do not have a better photo...this piece of a photo is all I could find, and note the extra red wire:
image.png

image.png

On Mon, Sep 6, 2021 at 1:43 PM Bill Hall <billhall95688@...> wrote:
How old is the battery disconnect switch or is it corroded internally?

On Mon, Sep 6, 2021 at 11:40 AM Paul Stascavage via groups.io <pstas2003=yahoo.com@groups.io> wrote:
Almost since purchasing our boat, we had a small negative leak that was indicated by the Masse Light.  The electrician in Martinique could not locate the source easily, but said that it was very small and to just keep an eye on the zincs.

Although I tried located the source of this myself many times by disconnecting individual bonding wires, I was never able to locate it.  However, our zincs would get us through 2 years of service with what I considered normal loss (about 30 - 40%) so it didn’t worry me much.

A few months ago, the Masse Light stopped illuminating and I thought maybe something may have fixed itself (wouldn’t that be great?).  But a few weeks ago, when I dove on the zincs, I noticed they had excessive loss and they are slightly less than a year old.

This morning I got out my volt meter, and we do still have a slight negative leak of about 0.009 volts when connecting the voltmeter to the negative post on the battery bank and the bonding wire on the rudder post, but when I checked the positive side, there was a full 25 volts leak indicated!

We recently had our alternator rebuilt so I disconcerted that and found no difference.  I also recently changed the switches on the windless, so I am going to disconnect those and check there as well.  We also had a new VHF radio installed and I will check that, but as that is 12 volts I don’t think that will be it.

I am definitely not electrically proficient, but what boggles me is that when I turn off the battery bank switches, I still show the leakage when testing from the bank.  How is it that with the battery bank isolated, I could still have current going to the bonding system?  What am I missing here?

Any insight and suggestions regarding where I should logically begin my search would be greatly appreciated. I am currently most uncomfortable with that kind of voltage in the bonding system.

Thank you in advance for any and all replies.

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Currently Exploring City Island, NY


www.RitaKathryn.com

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