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Discussion Starter · #1 ·
I'm in the process of adding shore power to my boat, which has no AC at all. I recently sold a Bene First 36.7 that was equipped with a shore power connector, which then went to a main breaker that was 6 feet from the inlet and still under the cockpit, then to the main panel that had another main breaker and several circuits. There was no galvanic isolator.

My plan for the new boat is a Smart Plug inlet with a galvanic isolator, then a main breaker close to the inlet, then to a main panel with another breaker. The first breaker will not be easily accessible.

My question is, do I really need two breakers? I realize the first breaker will protect in the event of a short between the panel and the shore power outlet (at the dock) but the dock connector has a breaker. If this is not required or beneficial I'm happy to omit it.

Thanks...
 

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I’m a fan of a double pole main breaker, so you know both legs are dead in the whole ship, if you're sticking your hand in something to fix it. Panel single pole breakers kill the hot leg, but you could theoretically short it to something else that is hot. Could be your arm doing the shorting. There is an ABYC standard for whether that double pole needs to be near the inlet, based up its distance to the panel. No doubt, it’s the safer way to go anyway, rather than have that one always live 6ft run.
 

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ABYC, Boat US and West Marine, all have fantastically simple articles written on this very subject. That way you won't have to trust someones opinion. If the explanations are way over you head, you may consider that you are not qualified to do it yourself.
 

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ABYC requires a main breaker within 10' of cable length from the inlet. No need for the additional breaker if within 10'.
ABYC requires either a double pole main breaker ... or ... a single pole main breaker plus a polarity indicator.
 

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Discussion Starter · #5 ·
ABYC requires a main breaker within 10' of cable length from the inlet. No need for the additional breaker if within 10'.
ABYC requires either a double pole main breaker ... or ... a single pole main breaker plus a polarity indicator.
Great thanks!
 

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I put in two single pole. It was a mistake I should have put in one single pole. I also put in a galvanic isolator made from a plan. The isolator must be able to handle full current e.g. 30 amps should a short to ground develop
 

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I put in two single pole. It was a mistake I should have put in one single pole. I also put in a galvanic isolator made from a plan. The isolator must be able to handle full current e.g. 30 amps should a short to ground develop
OOPS I meant one double pole, so if one trips so does the other.
 

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Discussion Starter · #9 ·
ABYC requires either a double pole main breaker ... or ... a single pole main breaker plus a polarity indicator.
I'm not sure how a single pole breaker would work, I'll research that. All the main panels I have seen have a double pole breaker and then 1 or more single pole breakers.

I'll email you thank you.
 

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I'm not sure how a single pole breaker would work, I'll research that. All the main panels I have seen have a double pole breaker and then 1 or more single pole breakers.

I'll email you thank you.
Single pole breakers with a polarity indicator are quite common on small to mid size sailboats.
Like this one on a Catalina 30
cat 30.jpg
 

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Does that mean only one side of the shore power is connected and in use?
No it means only the hot wire goes through the breaker, You still have your full 30amps
 
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My boat has a 30a main breaker just inside the transom that protects the wiring feeding the shore power panel. There is no main breaker on the panel, just individual breakers for each load. My boat is european so all breakers are double pole, but that is not necessary on 115v circuits. Typically in North America we only break the hot, not the neutral. The number of poles a breaker has is not necessarily an indication of how many poles it has. The breakers on my boat only have 1 handle even though they are 2 pole.



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ABYC requires a main breaker within 10' of cable length from the inlet. No need for the additional breaker if within 10'.
ABYC has good standards, but this is very representative of a bureaucratic type standard. At 9’11” they require no transom breaker. Add one inch and it’s required. There is no practical distinction. One would think cable size, loads, protected cable, etc, would factor in. I’m sure they expect the professional installer to use their head. Maybe it’s a standard that means, above 10’ you must, below 10’ use your head. Also, I assume they mean cable length, not length down the deck.

For me, I’d like a way to know that every wire on the boat is dead, both hot and neutral, when needed. Of course, one could always go to the pedestal and unplug.
 

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10 FEET plus or minus a few inches, give me an inch and I'll take a mile. None of this will come into play if nothing ever happens, but let a guess get electrocuted or a few boats get burned to the water, THAN the regulation will get very important.
 

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ABYC has good standards, but this is very representative of a bureaucratic type standard. At 9’11” they require no transom breaker. Add one inch and it’s required. There is no practical distinction.
- Your home building code has a similar standard.
So what length should it be ? ... 20', 40', 50' . And how would you arrive at that number ?
Or are you suggesting that this circuit protection should not be required at all ?

One would think cable size, loads, protected cable, etc, would factor in.
- Actually there are many other factors that you apparently are unaware of but detailing all 80 pages of that particular standard is not practical on this forum..
 

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ABYC has good standards, but this is very representative of a bureaucratic type standard. At 9’11” they require no transom breaker. Add one inch and it’s required. There is no practical distinction. One would think cable size, loads, protected cable, etc, would factor in. I’m sure they expect the professional installer to use their head. Maybe it’s a standard that means, above 10’ you must, below 10’ use your head. Also, I assume they mean cable length, not length down the deck.

For me, I’d like a way to know that every wire on the boat is dead, both hot and neutral, when needed. Of course, one could always go to the pedestal and unplug.
Breakers are intended to protect the conductors "downstream" of them, and theoretically the breaker on the dock is serving that purpose on the feeder coming into the boat, but because the circuit ampacity of the shore power circuit is unknown the boat's circuit needs to be treated as a new branch circuit. The 10ft is just being practical because the breaker needs to be located where it is readily as accessible. Sometimes codes are even more vague, and might say "as close as is practical" or "within reach of the energized equipment". (Remember ABYC is not actually code, it is more like "best practices")

With regards to "knowing every wire is dead" on a circuit, the reason on land 115v breakers only break the hot, and not the neutral is that the neutral is grounded so it cannot be live. You can touch the neutral on a live 115v circuit and you will not get a shock.

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- Your home building code has a similar standard.
So what length should it be ? ... 20', 40', 50' . And how would you arrive at that number ?
I would arrive at that number based upon one of two ways I mentioned. Either a multi factor method, based on the variety of factors you made an 80 page snotty comment on below, or clarify that the bright line is when one must have transom breakers, but below that the standard would encourage them based on circumstances. The yes/no brightline is bureaucratic and comparing it to home building codes only substantiates it. Analogous to idiot lights, for people who don’t understand.

Or are you suggesting that this circuit protection should not be required at all ?
Don’t be ridiculous. You know that’s not what I was suggesting.

- Actually there are many other factors that you apparently are unaware of but detailing all 80 pages of that particular standard is not practical on this forum..
Feel better? If there are standards that clarify the 10ft rule, it would help the OP to explain them. If not, this was subterfuge.
 

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You can touch the neutral on a live 115v circuit and you will not get a shock.
Right, but my point is, if you only opened the hot circuit you are working on, you could still short the neutral, from the circuit you're working on, with the hot from another live circuit. I prefer the whole boat is dead, including the 10 ft from the inlet to the panel. Can also be done by unplugging at the pedestal, of course, as I said.
 
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