Replies to This Discussion

Permalink Reply by Tom Hruby on July 14, 2012 at 2:36am

Hi Ralph,

I consulted "Google" and found two articles that might help you. They do a much better job of explaining how to set up your grounding system.  The first is from the University of Alaska Sea Grant Program and the second is from West Marine.

Tom

http://seagrant.uaf.edu/bookstore/boatkeeper/electrical-safety.pdf

http://www.sailmail.com/grounds.htm

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Permalink Reply by Roland Rodriguez on July 14, 2012 at 2:44am

Thanks very much for the reply Tom.  I did see those two articles.  They both make the assumption there is a negative terminal on an engine block to attach ground to.  Since I'll soon have an electric motor with no engine block I'm wondering where that ground attachment should move to?

Thanks again,

Roland

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Permalink Reply by Tom Hruby on July 14, 2012 at 5:32am

Roland,

It all depends on the connection you have between your prop shaft and your motor.  If you have  a direct metal to metal connection between the motor housing and the prop shaft you could ground it to the motor housing. The shaft and prop then act as the "grounding wire." If, however, you have some plastic or rubber isolating the shaft from the motor you will need to figure some way to ground the electric system to the shaft (e.g. some kind of conductive collar that lets the shaft turn).

The alternative is to attach a copper or stainless steel plate somewhere on the hull or the rudder to provide the necessary connection to the water.  If you have a sailboat I assume you have a lightning rod that is somehow grounded to the water.   If not I suggest you consider installing one.  The grounding plate for the lightning rod can also be used to ground you electric system.  I suggest you check into the size of the plate needed.  Somewhere in my dim memories the number that pops out is a plate 18 inches on a side.

The reason I would be concerned about lightning when using electric motors is that the motor and wires generate very strong electric fields that could attract lightning when you are in the middle of the ocean, especially if you have a metal mast that can act as conductor for the fields. 

I have first hand experience with the problems caused by the electric and magnetic fields (though not in thunderstorms... luckily!!).  I commented previously in this discussion that the eletric motors and wires create havoc with my compass.  When under electric power I have to navigate only by gps.  If I want to use a compass I have shut everything down.

Tom

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Permalink Reply by Martin Jønland on December 29, 2012 at 7:45am

Lightningrods on boats was a theme discused a lot when I was sailing. And I belive that if you "rod" your boat, it is muh more likely to get hit by lightning. Also i think putting this lightningrod through the hul is a bad idea, idealy it should (on sailboats) follow side waiers holding the mast and outside the hull and into the water.

Some sailors had Car-battery-starter-cables they put in bad weather.

 

Lightning is lokking for the easiest way to hit ground, sometimes thats through the mast of your boat ore through your ambrella. I never heard that theory that electric field can attrakt lightning before.

 

My AC is mostly used when on shorepower and then i get ground from there. When I run my generator I`m ungrounded and I realise that is potensialy dangerouse, Soo I dont touch the chargers, waterheater and generator when running the generator, but since I myself is rearly grunded when in the boat the danger is minimal. My Inverter is for ground free appliances only. So i dont realy see any reason to make more trouble out of it.

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Permalink Reply by mark clouse on July 18, 2012 at 12:31am

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Permalink Reply by Capt. Mike on July 31, 2012 at 11:09pm

Roland 

My 48 volt propulsion bank ground  is completely isolated from the DC/AC house grounds which connect up to a Dyna Plate located on the hull. So whatever was going to the former diesel block connects to the dyna plate. This was the recommended way to set things up when I bought my Thoosa 9000 system. It has worked well for five years now.

Capt. Mike

http://biankablog.blogspot.com

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Permalink Reply by James Sizemore on August 14, 2012 at 11:00am

Just curious does your dyna plate have a zinc attached?   Does your 48 volt bank float or is it ground via the shaft? 

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Permalink Reply by Capt. Mike on August 14, 2012 at 6:42pm

Jim:

There is no zinc on the Dyna Plate. I'm not sure if my 48 volt system is floating I suspect it is ground via the shaft (which does have a zinc) The zinc does show some degradation by the end of the season though not anymore than when I had my diesel. 

Capt. Mike

http://biankablog.blogspot.com

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Permalink Reply by James Sizemore on August 14, 2012 at 10:56am

If you want to get the ground back on the shafts, where your zincs are. You could use a shaft ground ring:

 http://www.est-aegis.com/datasheets/AEGIS_Bearing_Protection_Ring_C...

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Permalink Reply by Charlie Johnson on August 19, 2012 at 5:35pm

According to ABYC Standard TE30, the propulsion system ground is to be separate and isolated from the DC system ground.

Hope this helps.
Charlie

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Permalink Reply by James Sizemore on August 20, 2012 at 2:07am

As you can see below from the ABYC web site TE-30 is for electrical systems beyond 50 volts, most folk on the forum use 48 volt systems so would still use E-11, not TE-30. I will admit I have not read this years revision, has the below changed?


ABYC/ANS TE-30 Electric Propulsion System.
ABYC E-11, AC and DC Electrical Systems on Boats, is limited to the design, construction, and installation of DC systems that operate at a potential of 50V or less, and AC electrical systems that operate at frequencies of 50 Hz or 60 Hz, and less than 300V to extra-low voltage. But technologies for system voltages and frequencies greater than those allowed by E-11 are increasingly employed, especially in electrical propulsion systems. Standards used by other industries, such as automotive and light rail, have led to confusion about their propriety and applicability in a marine environment.
This Technical Information Report is a compilation of safety requirements of widely used national and international standards related to voltages and frequencies beyond those covered by E-11. It includes recommendations for the design, construction, and installation of electrical systems and components in high-voltage electric propulsion systems.

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Permalink Reply by Charlie Johnson on December 30, 2012 at 4:17am

True enough, but the concept is valid:  keep the propulsion system B- separate from the vessel ground.

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