Re: [electricboats] Grounding.

So I just read ABYC E-30. 

The requirements of the standard are for EP systems over 50 VDC. 

The question becomes does this standard apply to 48 volt drives? I know my battery bank fully charged rests at 51 volts. So would an installation be required to meet the E-30 standard? If anyone here belongs to ABYC could you ask for an interpretation. I think that would be very helpful for the group.

E-30 also requires an additional disconnect on the negative from the battery. It also requires monitoring devices which many have already incorporated into their systems.

Although the propulsion systems do not connect to a common ground like they do under E-11, the E-30 standard does require the motor housing to be grounded per E-11.

What I do know are the many people on this & other forums over a 5 year period that have advocated for a free floating propulsion system. Maybe they've had it right. 

Question for the group? When I post here I get 2 emails on the subject at hand. Do others see 2 emails from me or have the same problem.

Thanks,

Bob

On Fri, Dec 4, 2020, 2:35 PM James Sizemore <james@deny.org> wrote:

Grounding to the shaft via a grounding brush would be better then a through-hull as the shaft is expected to carry a ground and has zinc's installed on it:

https://www.cvjayaabadi.com/boat-parts-and-accessories/zincs-anodes/promariner-shaft-brush-20035/

On Dec 4, 2020, at 12:21 PM, Ryan Scott Dancey <rsdancey@gmail.com> wrote:



If you don't ground DC Neg, then you have a floating ground. That means the potential on the negative side might be zero. Or it might not.

If you have a floating ground, then you need to fuse both positive and negative because you don't know where a ground fault might occur. Yay double the cost and complexities of fusing!

If you have AC and DC power on your boat, and the DC negative is not bonded to AC safety ground, it is possible for stray AC current to enter the DC system. When this happens, AC current may enter the water around a boat and injure or kill swimmers near the boat.

The point of tying into the engine is not because "the engine is a massive block of metal", it is because the engine, via the prop shaft, is grounded to earth through the water. It would be better to use a bonding plate attached to the external side of the hull and bypass the engine but the engine is historically the point of the grounding system in the boat because it was convenient, worked, and a lot of boat systems were derived from automobile systems which grounded through a connection to the engine.

Electric motors may  be electrically isolated from the shaft (mine is; Electric Yacht QuietTorque 10kw). Grounding to the chassis of the engine doesn't do anything useful. My boat is old (1973) and does not appear to have an external grounding plate (future upgrade!) so I am going to have to ground to some other path to earth. My boat doesn't have keel bolts either. The least best, but perhaps only available, option is to ground via a metal through-hull (which brings with it concerns about corrosion).

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