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  #1  
Old 04-09-2008
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main breaker rating

Hi guys (sailingdog),
started chasing wires around my 35 year old sabre 28 and found no breaker after the shore power inlet. shore power is 30 amp so is this approprate :
http://www.defender.com/product.jsp?path=-1|328|296553|299262|825431&id=589879
or
http://www.defender.com/product.jsp?path=-1|328|296553|299262|825439&id=673241

thanks,
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  #2  
Old 04-09-2008
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Ideally, what you should have is a main AC panel that has two 30 Amp breakers (assuming that you're using a 30 Amp shore power cord and inlet socket). One will be for the Hot line and the other for the Neutral line. A good one for a smaller boat is this one:



It has two fifteen amp breakers for two AC circuits, and the third can be a 15 amp or 30 amp circuit, depending on what you need.

The reason for the two breakers is to prevent an AC shock hazard if the dock wiring has a reversed polarity problem...since the neutral line has a breaker in it.

Here is a basic wiring diagram for the AC Shorepower panel on a boat, using the panel I posted a link to above.



I hope that helps.
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Last edited by sailingdog; 04-09-2008 at 09:46 PM.
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Old 04-09-2008
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The panel in the picture may have two (15A or 30A) breakers, but those would normally be tied together so that if either one blew, they both blew. That's to ensure that a short or overload from either leg (hot or neutral) to ground, also shuts down all the AC on all legs. Not to provide two AC circuits!

Also, most safety codes today would require a GFI to be installed right at the AC feed to the boat, or as close to it as practical. That should be a priority before even a main breaker gets installed.

The schematic you have shows a potential for 60A of loads, that would be a very bad thing if you were plugged into a standard 30A or 50A dock line. It should be wired so that each drop circuit (battery charger, sockets, whatever) all are wired back to one source--which is the primary "dual" breaker that trips both sides (neutral and hot) and is rated for the supply capacity, i.e. 30A or 50A that the system is designed for.

The last boat I rewired lives on a mooring, we decided the entire AC system could be chucked. Makes the boat lighter & faster, and you gotta have lighter and faster![vbg]
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Old 04-09-2008
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The two 30 Amp breakers at the top of the panel are tied together with a bar. I never said it was to provide two AC circuits. It might help if your actually read what I wrote, from my previous post:

Quote:
Ideally, what you should have is a main AC panel that has two 30 Amp breakers (assuming that you're using a 30 Amp shore power cord and inlet socket). One will be for the Hot line and the other for the Neutral line.
Most diagrams of boat AC systems I've seen have the GFI on the circuit side of the panel, not on the input side... I'd have to check to see what the ABYC code says about it, but don't believe they require GFI protection on the AC input to the panel.

Yes, the schematic I have shows the potential for 60 Amps of loads, and that is something I am aware of. It actually wouldn't over load the dock line, since the primary breakers--the two 30 Amp breakers at the top of the panel--would trip before it could overload the shorepower cord.

The 30 Amp circuit was for an inverter/charger we installed on my friend's boat. The Freedom 30 draws a maximum of 28 Amps AC at full charge. Yes, I know the diagram says Freedom 20, but they went for the larger inverter due to the wife's requirements...
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Old 04-09-2008
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Interestingly, ABYC requires that both Hot and Neutral operate in sync.
There is, however, no explicit requirement for GFI at all. They tell you how to connect it if you have one, but not that you must have one.
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I did indeed read what you wrote, and after reading it twice posted my reply. After reading it a thrid time, I still read it as "It has two fifteen amp breakers for two AC circuits, " and that's directly below th epicture of the panel. I'm reading that to mean two matching breakers, the two at the top of the panel on the different sides of the AC main. And the next two references, to the next two breakers.
Apparently that's not what you mean--but it is how what you wrote can be read.

On the schematic...hmmm...five on the schematic, four on the panel.[g] With no rating shown for the top two in the schematic, one is free to make assumptions. There's always room for confusion. Ergh, Jello.
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The top two breakers are 30 Amp and ganged.. for the Hot and Neutral input to the panel. The third and fourth breakers are the 15 Amp breakers I was talking about. BTW, the photo wasn't of the panel I was working with, but the vendor's photo of the same product and is missing the fifth breaker. The way the panel was finally configured was:

1 & 2) Ganged 30 Amp breakers for input
3) 30 Amp breaker for Inverter
4 & 5) 15 amp breakers for port and starboard AC outlets.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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IMHO, it's not a good idea to wire an appliance which can draw up to 28 amps, together with other distribution circuits on the same 30-amp main switch panel.

Here's why.

1. The typical 30A connectors...male and female...found in use today are overrated. The load they can carry safely is often significantly reduced by poor contacts, surface corrosion, and other environmental factors. I would never trust a 30A connection to safely carry a continuous load of 30A. Much better to de-rate them to 20-25A. I just replaced the main 30A receptacle and dock cord on a clients boat today; it showed serious arcing and burning due to overload for the conditions (poor contacts, surface corrosion, slight overload, old wiring). It could have caused a serious meltdown or fire; we've seen lots of them at our marina, as I'm sure other long-time boaters have.

2. The setup in the diagram above is a disaster waiting to happen, especially for the unwary, tired, or forgetful sailor. Yes, the 30A breakers on the hot and neutral should trip when faced with a load much more than 30A, but only after some time; moreover, they could trip at the wrong time and cause a serious problem. For example, the tired weekend sailor returns to his slip on Sunday nite, plugs in, and sets out for home. The depleted batteries are hungry, the charger sucks a lot of amperage and, after a bit, the hot water heater kicks in asking for another 15-20A. Pop...the main breakers go, and the charger goes off along with the hot water heater. Result: no battery charging, no hot water (or other 110V appliance connected to the mains).

What to do?

Install a 2nd 30A circuit, or upgrade the AC system to a 50A circuit. Or, install a second, smaller battery charger which could happily co-exist on a single 30A circuit with other house loads.

Bill
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Bill has it spot on...
or, you could throw the whole basket out, put in a couple of inline fuses, just make sure you have plenty of aluminum foil around for emergency repairs.
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Old 04-10-2008
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I am aware of this, and told them this...they were not interested in doing it that way. BTW, no hot water heater on the boat, at least not an electric one.
Quote:
Originally Posted by btrayfors View Post
IMHO, it's not a good idea to wire an appliance which can draw up to 28 amps, together with other distribution circuits on the same 30-amp main switch panel.

Here's why.

1. The typical 30A connectors...male and female...found in use today are overrated. The load they can carry safely is often significantly reduced by poor contacts, surface corrosion, and other environmental factors. I would never trust a 30A connection to safely carry a continuous load of 30A. Much better to de-rate them to 20-25A. I just replaced the main 30A receptacle and dock cord on a clients boat today; it showed serious arcing and burning due to overload for the conditions (poor contacts, surface corrosion, slight overload, old wiring). It could have caused a serious meltdown or fire; we've seen lots of them at our marina, as I'm sure other long-time boaters have.

2. The setup in the diagram above is a disaster waiting to happen, especially for the unwary, tired, or forgetful sailor. Yes, the 30A breakers on the hot and neutral should trip when faced with a load much more than 30A, but only after some time; moreover, they could trip at the wrong time and cause a serious problem. For example, the tired weekend sailor returns to his slip on Sunday nite, plugs in, and sets out for home. The depleted batteries are hungry, the charger sucks a lot of amperage and, after a bit, the hot water heater kicks in asking for another 15-20A. Pop...the main breakers go, and the charger goes off along with the hot water heater. Result: no battery charging, no hot water (or other 110V appliance connected to the mains).

What to do?

Install a 2nd 30A circuit, or upgrade the AC system to a 50A circuit. Or, install a second, smaller battery charger which could happily co-exist on a single 30A circuit with other house loads.

Bill
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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