1GM10 earth/insulated return

[PerformanceSailor]

Similar discussion, Different continent

On any boat with an AC system there has to be an earthing connection for safety reasons and that is logically the engine block. This would apply to most boats. I know of no other way to safely do it. And you say you have no corrosion issues. If it isn't broken why try to fix it?

Interesting! We have a similar discussion going right now on the Ericson Owners' site about galvanic isolators, grounding, AC & DC.
My own boat, with a stock factory electrical system from 1988, appears to have no connection between the two ground busses. i.e. the AC buss and the DC buss bars are separate.

Sometimes I wonder... if there is much of anything standardized on boats!


LB

 

[noelex]

Beware of statement like "The seawater cooing provides a possible path for conduction and therfore corrosion of other metal structures such as the rudder stock." Made by Noelex. It is a red herring as far as connection between metal bits and pieces is concerned in the case of galvanic corrosion. The relevant connection is a connection with a metal conductor or direct contact .
One metal, seawater, another metal more seawater back to the first metal does not make a circuit for galvanic corrosion to occur.
.

Let me give just one example how a circuit can be formed and isolating the engine can reduce the potential for corrosion.
The autopilot is connected to the rudder stock. it has enough carbon build up to electrically connect the - supply to the rudder stock (this is reasonably common). The engine is also connected to the negative supply and both metals are suspended in an electrolite (seawater).

 

[VicS]

Let me give just one example how a circuit can be formed and isolating the engine can reduce the potential for corrosion.
The autopilot is connected to the rudder stock. it has enough carbon build up to electrically connect the - supply to the rudder stock (this is reasonably common). The engine is also connected to the negative supply and both metals are suspended in an electrolite (seawater).

Yes of course we understand that.

What I was trying to caution against is the idea sometimes put forward is that the inlet seacock, for example, is connected to the engine block via the water in the hose in the same way as a wire bonding between the two would connect them.

 

[Ubergeekian]

I have the 1gm10 and it's earth return wired.

Having read the thread, I still don't understand what you mean by "earth return wired". Is your boat made of metal?

 

[noelex]

Having read the thread, I still don't understand what you mean by "earth return wired". Is your boat made of metal?

"earth return wired" (in this contex) means the engine block is connected to the battery negative supply. The engine block can then supply the - power to things like the oil pressure sender. In an isolated engine the oil pressure sender requres 2 wires because the engine bloc will not supply the negative connection.
An "earth return wired" engine can be on a boat of any material.

 

[Tranona]

Thank you vicS

Your digression helped!

It has to be re-wired whatever so I figure I may as well follow the best advice I can get.

As it is the main battery switch doesn't disconnect the power in either the on or off positions..... reason enough to re-wire!!!!!

I think that concludes this thread and thank you all once again.

Out.

Would I be right in thinking that you have a Contessa 26? If so I cannot think of a more simple unsophisticated boat to wire up. You have none of the kit that creates galvanic problems, particularly if you have no shore power, no exotic feathering prop, no fully integrated electronic navigation system, don't moor in a marina with lots of steel piles and other boats on shore power around etc.

Just keep it simple. Two banks of batteries, one to start your engine (basic diesel car battery or preferably a dedicated starter battery such as a Red Flash or Odyssey). One service battery around 110-150ah - leisure battery, lead acid or AGM depending on the depth of your pocket and the way you consume electricity. BEP Marine switch cluster to isolate both banks and parallel if you need to. VSR to split the charge between the two banks. A 12 volt DC switch panel with fused circuits for all your domestic and navigation needs. Job done. All the rest is a waste of time. If you do not currently have any problem with galvanic corrosion of the two key components - stern gear and skin fittings, nothing is going to change by re-wiring.

I have exactly this kind of system on my 26 footer, with the addition of a small solar panel to keep the service battery topped up when I am not using the boat, and an inverter to run a lap top when I get bored.

As I said earlier, James designed and supplied the whole system for me apart from the distribution panel which I had custom made by Taplin to the same standard as they supply to all the major UK boatbuilders and the RNLI, but this was an indulgence and I could have saved a couple of hundred by making it up myself - but I would not have got an integrated mimic of my boat for all nav lights nor built in repeater instruments - neither really necessary.

 

[VicS]

Would I be right in thinking that you have a Contessa 26?

and called Red Admiral

 

[Ubergeekian]

"earth return wired" (in this contex) means the engine block is connected to the battery negative supply. The engine block can then supply the - power to things like the oil pressure sender. In an isolated engine the oil pressure sender requres 2 wires because the engine bloc will not supply the negative connection.
An "earth return wired" engine can be on a boat of any material.

Thank you.

 

[Stu Jackson]

Interesting! ...My own boat, with a stock factory electrical system from 1988, appears to have no connection between the two ground busses. i.e. the AC buss and the DC buss bars are separate.

Sometimes I wonder... if there is much of anything standardized on boats!

I agree about interesting. Standardization on boats occurs, it seems, only in saving money during production. Like the alternator output going to the C post of the 1-2-B switches.

Our AC and DC systems are not connected either. Came that way from the factory. I have had no trouble in 12-1/2 years of ownership with any corrosion.

I've read Calder's (2nd Edition) and do not think it's worth the albeit minimal effort to connect them.

Your boat, your choice.

 

[cimo]

Basically (because I am), I want to remove the engine earth bonding and take it all to a "common earth point" where it can then go back to the battery negative. As I understand it (?!) any earth leak then finds its way back to the batteries rather than out of the prop shaft and therefore contributing to galvanic corrosion.

Many thanks,

Guy.

Hello Guy
You concern is earth leakage? from what precisley?

Electrical current will always find the path of least resistance & I feel you'll get bigger dividends making sure all your connections are clean, sound and protected as much as possible from the environment.

If you do remove your engine from the installations -ve, then I would recommend you consider making other grounding arrangements such as a hull plate (external). In the "unlikehood" of a direct lightening strike, you may be glad. You engine and prop are currently providing this dissipation path thru the electrical installations -ve wiring.

I honestly can't see the benefit of doing what you propose on a GRP hull.
You don't appear to be having corrosion issues at the mo?

(good luck with the re-wire).
rgds
c

 

[cimo]

I agree about interesting. Standardization on boats occurs, it seems, only in saving money during production. Like the alternator output going to the C post of the 1-2-B switches.
QUOTE]

Which happens to be a very cost effective method of charging batterys with some added safety benefits too!

(couldn't let you away with that stu )

 

[steve28]

It's a 35 Amp alternator (un-insulated) and a GRP boat.

"There is no AC involved".

It isn't broken, it just needs upgrading!

So i sssume it not the original hitachi 35a alternator thats insulated earthout put then ?

Steve

 

[Bilgediver]

Thank you vicS

Your digression helped!

It has to be re-wired whatever so I figure I may as well follow the best advice I can get.

As it is the main battery switch doesn't disconnect the power in either the on or off positions..... reason enough to re-wire!!!!!

I think that concludes this thread and thank you all once again.

Out.

Seems a simple fault to fix?????? Not a reason for rewire.

Don t forget that in the 70s many boats had the isolator in the negative
line!!!!

Vic took most of the words from my mouth and I suspect like me has reservations about some of the things Nigel Calder writes especially when
out of context. This strapping business is a typical case.

I agree with others here that there is no advantage to what you propose when applied to a GRP boat.

 

[pampas]

co256

I understand that the alternator isn't insulated and should be for that perfection that you talk so fondly of, but surely a heavy copper cable from the alternator case to a "common ground point" would provide an easy path for earth leakage and therefore remove that same earth leakage from the engine block???

Thanks again!

By doing The later part of your paragraph all that you would do is to lower the resistance path from th alternator case to earth.
Think that you have become a bit confused about leakage.

A, Is the electrical path from the boat to water that you are concerned with, or B, Any electrical path from the insulated part to the negative.?

The reason I ask is that on metal hulls especially Aluminum the engine earth return is a killer for the boat. worked on many that are insulated and no means fitted to determine if the sytem when operating is in fact still double insulated.

 

[lw395]

Evening all,

I have the 1gm10 and it's earth return wired.

I'd like to change to insulated return as recommended by any source I've found (t-b training, Calder).

Anyone had any experience of this?

Any problems to look out for?

Basically (because I am), I want to remove the engine earth bonding and take it all to a "common earth point" where it can then go back to the battery negative. As I understand it (?!) any earth leak then finds its way back to the batteries rather than out of the prop shaft and therefore contributing to galvanic corrosion.

Many thanks,

Guy.

If you have no shore power this is entirely pointless.
The DC system only makes one contact to the sea, via the propshaft, so there is no circuit, so no galvanic corrosion from this source.
Unless you have a shortwave set earthed to the ocean or some other path you're not telling us about?
Find something more useful to do, like going sailing!