Insulated Earth

[alan54]

I am re-wiring my Bukh 20 engine and want to use an earth insulated system, on my steel boat. Can my starter and alternator be altered to earth insulated units or do I need new units ?
regards
radar

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[tristan]

you will need new units unless you can get some insulated adaptors made up - probably unlikely, but worth looking into.

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[pampas]

As already suggested,you will need new units, Dont forget that all other bits will have to be altered as well. ( Temp. oil, Rev counter,)cheaper to use steel hull as the return and fit good anodes. possibly invest in electrically driven protection system.

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[HaraldS]

If your alternator isn't a two pole version, you'll need to get a new one. WIth starters this isn't necessary, and you'll find it hard to find a two pole starter that fits. The usual way to do it is to take a ground isolating solenoid/relais, powerfull enough to take the approximately 100Amp of the starter. The coil of that is wired parallel to the regular starter solenoid. On the load side the engine block goes to one terminal, the other goes to your newly isolated ground. The result is that the engine block is only grounded while you are cranking.

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[MainlySteam]

<<<cheaper to use steel hull as the return and fit good anodes>>>

Don't do it.

Apart from the possible corrosion issues (which anodes will not provide protection for either), using the hull as the negative return (as does bonding the negative bus at the board to the AC ground, which should be avoided in my opinion) creates the risk of fire for any positive conductor short to the hull. A common place for fire to occur on any vessel is at the engine itself if the engine is grounded and a positive conductor shorts to the engine (I can recall at least one forumites personal experience of this in the last few months). In a small metal vessel, using the hull as the negative return (or otherwise grounding the negative to the hull) creates the same risk throughout the vessel.

John

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by MainlySteam on 25/09/2003 00:02 (server time).</FONT></P>

 

[DMGibson]

I think it depends on the units. I have successfully converted CAV (Lucas) alternators to insulated return working, simply by putting insulating washers on the negative terminal.

As to starter motors, Lister's use insulated return motors on their engines as standard, so they are available.

Suggest you take the units to an independant auto electrician and explain what you want.

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[Gunfleet]

Also, if you've got any of your anode fitting wrong, you'll find out by way of a hole in the boat.

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