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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance > Electrical Systems
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Old 03-01-2009
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Earth Leakage Circuit Breakers

My understanding is that an earth leakage (ground fault) circuit breaker (for high volatage AC) will detect a short to ground from one of the two active cables and pop the circuit breaker to stop the power before it can do any damage. The circuit breakers pop much more quickly than a regular CB.

My question is do most people install these? I had a boat electrician rewire some of my boat and he did not install one.

I don't believe the AC inverter has one, but I could be wrong.

I read on another unrelated thread that each AC outlet should have a GFCI incorporated into the outlet. I have a single outlet, but it is not Ground Fault protected. I guess it is possible to add one of these afterwards?

Last edited by matt2; 03-01-2009 at 10:50 AM.
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Old 03-01-2009
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Quote:
Originally Posted by matt2 View Post
My understanding is that an earth leakage (ground fault) circuit breaker (for high volatage AC) will detect a short to ground from one of the two active cables and pop the circuit breaker to stop the power before it can do any damage. The circuit breakers pop much more quickly than a regular CB.
?
Matt, an earth leakage breaker detects current in the Neutral wire only - the theory being that if the currect going out (in the Active) isn't exactly the same as that coming back (in the Neutral), then it's going someplace it shouldn't (like you).

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My question is do most people install these? I had a boat electrician rewire some of my boat and he did not install one.

I don't believe the AC inverter has one, but I could be wrong.
Everyone should (if they have a shore-power connection) - but most people don't.

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Originally Posted by matt2 View Post
I read on another unrelated thread that each AC outlet should have a GFCI incorporated into the outlet. I have a single outlet, but it is not Ground Fault protected. I guess it is possible to add one of these afterwards?
Whether or not you use GFCI Outlets depends on how many you have in the boat. If you only have one, then it's usually cheaper to replace the existing outlet with a GFCI version. If you have many, it's usually cheaper to install the GFCI as part of the AC main switch.

I hope this helps.
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Old 03-02-2009
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to simplify what hartley said, a gfi compares the amount of amps going out thru the hot wire and back in thru the neutral. if there is over 5 milli amps difference it shuts off. the idea is if you contact the hot and a ground you allow some voltage to not go back thru the neutral. now getting between the hot a neutral it wont do a thing. they cost about 10 bucks each, so like hartley said if you dont have a bunch just changing each maybe easier. but you need to look at the box the receptacle is in, it may not be big enough.

you could add one at the panel to protect all outlets, but thats an over kill, personally i would just do the ones at the sinks. i dont have any on my boat and probably wont install them either. my reasoning is i dont use shore power much, and everything i would use has a ground pin on the plug so any shorts will trip the breaker. also my sink is plastic, there is no real metal to grab on my boat so there is no real way to get a shock. BTW i am a master electrician

but to each his own, dont take my word as the way to do your boat
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Thanks guys. Now I understand.
So that means it will still work with devices that do not have an earth wire.

Actually I do not really have an AC switch just an inverter on remote switch on the CB board.
The inverter has a switch on it and has fuses in the inverter box itself.
If I connect AC to the charger, any AC I get is still from the inverter.
i.e. the charger converts to DC charges the batteries and the inverter runs off the batteries.

Most of the time the inverter is switched off at the both the inverter remote switch and a hard switch on the inverter.

I think I will add a GFI or change the single outlet to one with a built in GFI.
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A good way to install GFI protection, within their current limits, about 20A, is to install a 'no face' unit behind the main breaker and connect all outlets to it rather than trying to replace individual outlets. That way, all outlets are downstream of it. You can put GFIs at the port / stbd split if the boat is set up that way.
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A good way to install GFI protection, within their current limits, about 20A, is to install a 'no face' unit behind the main breaker and connect all outlets to it rather than trying to replace individual outlets. That way, all outlets are downstream of it. You can put GFIs at the port / stbd split if the boat is set up that way.
Howard Keiper
Berkeley
That's a good idea, but the problem with the 'no face' versions are, on a boat, if they trip there's usually no easy way to reset them. I mean, first you have to find the bugger...
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Not a problem at all...I know where my GFI is....I only have one. A side benefit: replacing an existing outlet with a GFI is always a major problem for me. There is never, ever enough room for the a GFI in the same space as the replaced receptacle; so, I don't replace, I add, somewhere else, first in line, in an inconspicuous place since nothing is expected to be plugged into it anyway.
Much, much easier to do.
Howard Keiper
Berkeley
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