Bonding System and Galvanic isolator - SailNet Community

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  #1  
Old 08-11-2008
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Bonding System and Galvanic isolator

Our galvanic isolator is going off, which of course is indicating some stray current. I am suspecting it relates to the bonding system.

I don't totally understand the bonding system, but it consists, on our boat, of a large green wire between the bronze thru-hulls. Apparently the bonding system is connections between metal fittings to short out any voltages that might otherwise develop.

The galvanic isolator started beeping this weekend (after a storm) so I looked at where the bonding wire (a large green wire) connects to the 50amp connector. It goes to the Quicksilver Galvanic Isolator, as do the the wires to the bronze thru-hulls. The bonding wire was loose and popped out of the connector. I stuck it back in but couldn't get the galvanic isolator to stop, so I just turned off the shore-power breaker for this week while we're not there.

I realize it could be stray current from another boat, not ours, but when I turn off our shore power it stops. So I am thinking it is where the bonding wire goes into our 50 amp connector.

Does anyone have any suggestions as to where our problem could be and what tests to do to check it? Any keys to replacing this inlet?

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Old 08-14-2008
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I believe the reason is...

The function of the isolator is to detect and use the shore-based ground via the shore power plug. This is to isolate your boat ground from the AC circuitry when a properly functioning ground is available. When the shore ground fails, you GI detects it and uses your boat ground for the AC system.

If your GI has done that, either the shore ground has failed or the GI is malfunctioning. Check the shore plug for a properly functioning ground.
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Old 08-14-2008
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h2obo is correct. The GI is telling you that you no longer have a working ground to the dock. The storm could have destroyed your GI or you have another problem with the AC ground system (possibly the shore connection). The GI will not tell you if you have a problem with your bonding system. A ground problem with the AC system makes it more dangerous and it should be fixed.

I would plug a circuit tester into an outlet to check if it also says you have an open ground. Then jump across the green wire connections on the GI. If the circuit tester then says you have a good ground then you have a Bad GI.
Careful here, you are working on the AC system - it can kill you (your 12 volt system probably wont). Unless you have another problem, working on only on the ground system is pretty safe. Turning off the shore power on the dock before connecting the jumpers would be a safety precaution.

There may be other ways to test the GI that someone else can chime in with.

Circuit tester...

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Old 08-14-2008
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Quote:
Originally Posted by h2obo View Post
If your GI has done that, either the shore ground has failed or the GI is malfunctioning. Check the shore plug for a properly functioning ground.
Thanks h20bo and Steve,
The big green bonding wire connects to the 50 AMP inside of the inlet on our boat, and I suspected that was the problem. It was loose but when I put it back in the GI still was still going off. Am I correct that the bonding wire is different than the ground? The bonding wire is the big green wire that goes to the GI and connects to all of the thru-hulls. My understanding is that it is for dispersing current in the even of a lightning strike or a fault.

I think I am going to put in a new inlet and hope it corrects the problem. I will try the circuit tester. Thats a good idea.
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Old 08-14-2008
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Any chance your GI also provides a reverse polarity feature and alarm? Not sure from your post of the model of GI you have.
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Old 08-14-2008
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Its a Quicksilver...I don't know the model # right now...I'll have to find that.
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Old 08-14-2008
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Your bonding system connects thru-hulls and other metal parts in contact with seawater. This allows your zinc to protect all items that are bonded together. However, the connections must be very very good because you are dealing with very low voltages here.

There are different theories on lightning protection. Different boat builders handle it different ways.

The primary purpose of the green wire running through the GI is to protect you if your AC power system has a problem. It also happens to be connected to your bonding system, but that's not the main reason for the GI and AC ground wire.
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