Open ground

LongJohn · Nov 21, 2016

I installed a new GFCI 110v outlet on the fly bridge. I pulled new 14/3 boat wire from the main AC distribution panel and terminated Hot to an unused breaker, and neutral and ground to the appropriate buses. Everything works fine except that a circuit tester shows "Open Ground". Investigation shows that every outlet on both 30A legs shows "Open Ground". Ground is good according to the tester at the dock power pedestal. Tester shows that the ground is good when the generator is running.

It's a 2005 Mainship 34T. It has isolation transformers but I don't understand them. Can some erudite person please help me understand, tell me where to look and what to fix?

Thanksalot

DavidM · Nov 21, 2016

Mainship installed the isolation transformer improperly in my 2006 34T, so maybe the same thing happened to yours. The load side ground on the isolation transformer was not connected. It needs to be connected to the transformer case. After I did that the outlets showed that the ground was fine using a plug in tester.

Go to Charles website and download the installation manual for that transformer for more details.

David

rwidman · Nov 23, 2016

LongJohn said:
I installed a new GFCI 110v outlet on the fly bridge. I pulled new 14/3 boat wire from the main AC distribution panel and terminated Hot to an unused breaker, and neutral and ground to the appropriate buses. Everything works fine except that a circuit tester shows "Open Ground". Investigation shows that every outlet on both 30A legs shows "Open Ground". Ground is good according to the tester at the dock power pedestal. Tester shows that the ground is good when the generator is running.

It's a 2005 Mainship 34T. It has isolation transformers but I don't understand them. Can some erudite person please help me understand, tell me where to look and what to fix?

Thanksalot

If the grounds are showing open for all the original outlets, then the part about the new one is irrelevant. You need to find out why your boat's ground buss is not connected to the ground on the shore power at the dock. Obviously (to me), the first thing you should do is try a "known good" shorepower cord. Borrow one that works and try it.

Then trace the ground conductor through the boat from the inlet connection until you find a disconnected cable. If all else fails, call in a qualified marine electrician. You really want that ground for safety.

LongJohn · Dec 7, 2016

David''s note was exactly correct. OEM installation failure of the isolation xfrmrs. The boat has been without AC ground while on dockside power since new - 3 owners and at least 4 surveys. Easy fix, once you get within reach of the xfrmrs. Manufacturer's schematic clearly shows how it should have been done.

Open ground

LongJohn

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DavidM

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rwidman

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LongJohn

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