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Old 01-02-2017, 09:46 AM   #1
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City: Pensacola, FL
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Vessel Name: Sea Triscuit
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Neutral to Ground

I'm preparing to install an inverter and noticed that the neutral and grounds are tied together on both 110v panels on the boat. My understanding is that, without an isolation transformer, this is incorrect and potentially dangerous.

To rectify, I will need to remove the jumpers, ensure proper connections to the ground and neutral bars of both panels, check to make sure the panels will ground through the shore power connections, and check the generator to make sure it automatically bonds the neutral and ground when it is the power source (the inverter is setup to). So, I will need to trace the ground and neutral connections all the way back to the shore power outlets for continuity and to confirm that neither relied on the other to provide a path.

Sound right? Thanks

I'm a little surprised the surveyor didn't catch this when we bought the boat. Odd?

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Old 01-02-2017, 05:44 PM   #2
City: Port Orchard, Wa
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Your RIGHT (that's wrong!) ... If your shore power's cord neutral were to break or make a bad connection, any 120 vac load onboard is going to try to find an alternate path back to the commoned up neutral / ground point on your shore power box.
If the ground wire in your cord is still working, it would at least find a "working path" for the 120 vac neutral half BUT this is BAD JUU-JUU! Any voltage drop in the ground wire (which is never intended to carry power) will make for a nasty electrolysis issue .... But Worse Yet .... if the ground wire were to also fail then you could have 120 vac between any grounded metal on your boat and the shore power box (when any 120 vac circuit is "turned on"). Maybe the boat had an isolation transformer at one time or maybe some "House" electrician wired the boat.
Be careful and go slow. Vic

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Old 01-02-2017, 06:55 PM   #3
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Yes, that is a bad situation and very dangerous. Your plan makes sense. AC neutrals should be tied to ground at only one place- the source. The source is your marina's shore power panel, an isolation transformer if you have one, your genset or your inverter. Make sure that the genset transfer switch transfers both the hot and the neutral so you can keep the two systems isolated.

A surveyor won't open up the panel and look for cross tied neutral/grounds. All he will do is assure that there is proper polarity and a ground at the outlets.

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Old 01-02-2017, 07:40 PM   #4
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City: Pensacola, FL
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Thanks guys. We'll be off shore power in a few days for the next few months, so I'll have some time to get it figured out and done right. Time to make sure I've got plenty of extra wire on the boat!
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