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mkmarine avatar image
mkmarine asked

2 x quattro 1 boat. Not coupled

Question on grounding and AC safety.

I'm wondering about bonding from chassis of inverters to the negative of the boat. With one inverter this makes sense and is the done thing. But with 2 with a potential for one of them to be inverting (neutral to ground) and the other in pass through (earth is neutral of other inverter or worst case reverse polarity negavite is live!)

Anyone with experience in this set up?.

This boat is set up with 1. 5kva quattro to run essential computer power. and general services from another 5kva quattro. They are not linked.


They have separate battery banks and both supply separate ac panels but share AC ground.

They are fed from either shore power or generator.


installation
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jwfrary answered ·

Should be connected to a ground plate in the hull. but not the anodes or negative bus of the boat.

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mkmarine avatar image mkmarine commented ·

Does that not create 2 different voltages in the water between bonded metals and ground plane giving galvanic corossion?

The idea with bonding to negative is if pos shorts to chassis the fault current will be enough to blow the fuse. If its not bonded to neg it could find a path through boats bonding / earth back to positive, which would not be enough to blow fuse?

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jwfrary avatar image jwfrary mkmarine commented ·

The bonding and DC earth are usually interconnected at the engine block. Connecting it elsewhere as well will encourage exactly as you describe and is to be avoided.


Assuming your RCD protected....There won't be any voltage on your AC earth as if there is your RCD will trip. But it does have to be connected to a ground plate. - The proper way to do it.

In the event, you have a fault where the dc has AC on it for some reason, then the rc should trip. b the current can find its way to earth (though the bonding system anyway. )

when ashore if using an isolation transformer you need to take steps to ensure there is adequate earth. jumper cable in the isolation transformer and if your particularly cautious a bonding strap to ground. (Rarely seen except for the military)

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