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A/C grounding question

Barr88

Member II
So I'm refitting my A/C line to observe the 10 ft rule. The box will be pretty close to the engine compartment. So I'm wondering if I can install a ground bus in the breaker box, connect the incoming ground to the bus, run a separate wire from the bus to the block and the run another ground to the outlets. Or does the ground need to go from the last outlet to the block? Hope I explained that fairly well
 

stillwater

Member II
AC safety grounds

Simple shore power safety grounds need not be routed to the ships grounding system if the shoreside system is trusted. ie: most cities with good functioning port facilities.

The exceptions are if you are using inverters or generators. Inverters/gensets need to have their safety grounds run to ships ground.

Having your grounding system tied to shore power opens you up to electrolisis differential from your neighbor that may have a less than perfect setup. If you have a "clamp on" AC amp meter, check your and your neighbor's AC shore power cable. If you see any differential, that boat's system is leaking AC through the ground, and to the water if the ground is tied to ships ground, and to your boat if the ground is tied in.
.5 amp differential is a lot but I've seen more.

Don't forget the GFCI as an important part of AC safety.

Have fun,
"Sparky"

AKA Dal
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Where to get on the Buss

On our '88 model, the AC ground buss bar is separate from the DC minus buss bar.
Some folks say to connect up the two "grounds" and some say it leads to other problems and not to do it.
I have left them separate. I could be wrong...
:rolleyes:

Loren
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Loren. Does your ground bus connect to the engine?

Only the DC Neg. buss connects to the block. Matter of fact there is a common DC "ground" bolt for all of the big black DC wires on one side of the base of the bell housing.

LB
 

Barr88

Member II
Yeah I have all my dc grounded there. I thank you so much for all your great advice. I was getting myself all wound up about the ac issue. I think I was just having a hard time figuring out what don Casey was trying to explainin his electric book. Oh well. Thanks again
 

Maine Sail

Member III
If you want to wire to current suggested and accepted marine standards:

ABYC E-11

11.5.5.3: The main AC system grounding bus shall be connected to

11.5.5.3.1 the engine negative terminal or the DC main negative bus on grounded DC systems, or

11.5.5.3.2 the boat’s DC grounding bus in installations using ungrounded DC electrical systems.

11.5.5.4: In AC circuits, all current carrying conductors and the grounding conductor shall be run together in the same
cable, bundle or raceway.

11.5.5.5: There shall be no switch or overcurrent protection device in the AC grounding (green) conductor.

11.5.5.5.1 Where isolation of galvanic currents is desirable, only devices meeting the requirements of ABYC A-28, Galvanic Isolators, shall be used in the grounding path.
 

Barr88

Member II
The concussion is back. It seems that if I ground the ac to the engine I put my boat at risk while plugged in at the marina. While if not grounded I put myself at risk. I thought that was the idea of the reverse polarity indicator. What is the lesser of two evils I certainly don't want to fry myself but at the same time I don't want an issue where I damage my boat (prop shaft) Orsomeone elses boat. I really don't want to be the cause of damage to someone elses boat. It seems to me that not grounding the ac and being prudent about testing the shore terminal and observing for reverse polarity is the better option for me. Can anyone convince me otherwise?
 

Emerald

Moderator
If you put a galvanic isolator in with the A/C wired per ABYC standards, you can both keep from killing swimmers etc. and keep stray current from eating your prop. :cool:
 

Barr88

Member II
Ok, looks like we have some resolution. Ground the green and use an isolator. Responding before my online search for an isolator. Please be cheap. Please
 

Tom Metzger

Sustaining Partner
The reverse polarity indicator

The reverse polarity indicator is not for detecting bad grounds. It tells you that the hot wire and the neutral wire are reversed. Basically, it tells you that the shore power connection or your shore power cable or your boat are wired incorrectly. This condition can be very dangerous.

The neutral of the shore power should never be grounded on your boat.
 
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