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Discussion Starter #1 (Edited)
On my simple electrical system, the PO used a rather crude on/off breaker on the wire that supplies DC to a bus, then the switch/fuse panel. I'm guessing its a AC breaker, but if it was ever DC marine rated, things have changed!

The wire is 10AWG, and runs 1 foot from the battery switch to the bus (including the breaker), then about 15 feet from the bus to the switch/fuse panel. The bus would probably rarely draw 20 amps at one time, and everything on it (other than the wire to the panel) is fused.

I'd like to replace the breaker with a marine grade auto/manual circuit breaker. Would this be an appropriate replacement?
http://www.genuinedealz.com/circuit-breaker-bussmann-185-series-surface-mount-30-amp

BTW...the existing breaker is rated at 50AMPs, "Max volts 32 125", Trip amps 62.5.
Other than being able to shut down the system manually, was it even providing any protection?
 

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I see AC breakers used quite a bit on DC circuits because they're cheap - but AC-only breakers aren't designed for DC and under some scenarios can catch fire. It sounds like the AC breaker you have is providing crude short-circuit protection, but little else.

Assuming your load is ~20 amps as you say, what you're proposing sounds like a vast improvement over what you have. Go for it. :)
 

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Discussion Starter #3 (Edited)
Assuming your load is ~20 amps as you say, what you're proposing sounds like a vast improvement over what you have. Go for it. :)
Thanks.
I'm confused though. I saw another thread where they were asking about replacing the DC (Edit: I meant AC!) shore power breaker. The breaker that was recommended was 15 Amps. Surely the potential for more amperage is greater on a AC Circuit. Though, I think they were using 14 gauge wire (seems light doesn't it?).

I know that the Breaker protection should be based on the size of the wire (in my case 10 Gauge). Is a 30 amp breaker too high a threshold to protect 10 gauge wire? The only choices in the breakers I'm looking at are 30 and 50 Amp. Anyone have a chart on wire size appropriate breaker/fuse size? I've looked, and surprisingly haven't come up with anything. I could go to one of my books and find a formula, but don't want to spend anymore time than I already have. I'll call the supplier, but would be interested in any thoughts.
 

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Thanks.
I'm confused though. I saw another thread where they were asking about replacing the DC shore power breaker. The breaker that was recommended was 15 Amps. Surely the potential for more amperage is greater on a AC Circuit. Though, I think they were using 14 gauge wire (seems light doesn't it?).

I know that the Breaker protection should be based on the size of the wire (in my case 10 Gauge). Is a 30 amp breaker too high a threshold to protect 10 gauge wire? The only choices in the breakers I'm looking at are 30 and 50 Amp. Anyone have a chart on wire size appropriate breaker/fuse size? I've looked, and surprisingly haven't come up with anything. I could go to one of my books and find a formula, but don't want to spend anymore time than I already have. I'll call the supplier, but would be interested in any thoughts.
120VAC shorepower cords used in 30A circuits should be 3-wire 10 guage to the boat inlet. The wiring inside the boat should have a CPD device (fuse or breaker) within 10 feet of the incoming connector. The breaker should be the double kind, breaking both the ungrounded black ('hot") wire and the grounded white ("neutral") wire. The grounding wire (green) should not be broken.

Breakers for distribution circuits normally are sized to protect the wire, but may be of lower capacity for extra safety and to protect connected devices.

50A circuits need AWG6 cabling. again, with double 50A breakers on the boat.

I'd suggest a trip to West Marine or Amazon.com to pick up a copy of Charlie Wing's book on basic electrical wiring on boats. This book, like most all electrical texts, contains tables on wiring ampacity and recommended CPD size.

You can also find charts online....Google is your friend :)

Bill
 

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Thanks.
I'm confused though. I saw another thread where they were asking about replacing the DC shore power breaker. The breaker that was recommended was 15 Amps. Surely the potential for more amperage is greater on a AC Circuit. Though, I think they were using 14 gauge wire (seems light doesn't it?).

I know that the Breaker protection should be based on the size of the wire (in my case 10 Gauge). Is a 30 amp breaker too high a threshold to protect 10 gauge wire? The only choices in the breakers I'm looking at are 30 and 50 Amp. Anyone have a chart on wire size appropriate breaker/fuse size? I've looked, and surprisingly haven't come up with anything. I could go to one of my books and find a formula, but don't want to spend anymore time than I already have. I'll call the supplier, but would be interested in any thoughts.
Blue Seas offers the type of breaker you linked to in 25, 30, and 40 amp sizes.
285-Series - Blue Sea Systems

The fuse or breaker should be larger than the expected load and smaller than the ampacity of the wire. 10 gauge unbundled inside an engine space has an ampacity of 51, 60 outside engine spaces.
Allowable Amperage in Conductors - Wire Sizing Chart - Blue Sea Systems
 

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Requirements for AC main breakers on boats changed as of Jan. 1 You should read:

Electric Shock Drowning (ESD) Explained - Seaworthy Magazine - BoatUS

Last fall I retro fitted a Blue Seas ELI to my boat and in doing so learned a few things. First West Marine sold me the breaker but there was no panel to mount it. Blue Seas bailed me out by selling me (thru West Marine) an oem version of their new panel. Second they spec'ed a 12 guage out of the breaker to the Hart Inverter, but since most docks have 30 amp and the Smart Cord is likewise 30 amp, I elected to go with 10 guage from the inlet to the ELI.

Things have evolved and now you can buy the ELI with a truly ugly suface mount box. I encourage you, after reading the attached documentation to tackle this not so difficult conversion. The life you save might just be mine.
 

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L124C is referring to a DC breaker, not an AC breaker.

The change in requirements for an ELCI is one, a recommendation, and two, for new construction.
 

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Discussion Starter #8
L124C is referring to a DC breaker, not an AC breaker.

The change in requirements for an ELCI is one, a recommendation, and two, for new construction.
True, but still worth a read. Besides... it made me feel good to FINALLY see an advantage to having a boat in salt water!:laugher
 

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BTW...the existing breaker is rated at 50AMPs, "Max volts 32 125", Trip amps 62.5.
Other than being able to shut down the system manually, was it even providing any protection?

There are breakers rated for DC & AC service. The typical DC voltage is 32 so what you have is a AC/DC rated breaker. If it is working then it should be ok as is. If you want to change it that is ok too.
 

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Discussion Starter #12 (Edited)
There are breakers rated for DC & AC service. The typical DC voltage is 32 so what you have is a AC/DC rated breaker. If it is working then it should be ok as is. If you want to change it that is ok too.
Now I'm REALLY confused. I thought typical DC systems were 12 or 24 volts. I've never even heard of 32! Please enlighten me.

BTW, the old breaker is showing signs of internal rust, so it's definitely time to replace it. Unfortunately, the speed wheel is located in the battery compartment, so so it takes in salt water every time I swap the plug for the wheel! Nothing but wires get wet, and I flush the compartment with fresh water. However, it's obviously not a great environment for things electrical. One reason I seldom use the wheel. The other being, I don't need to know how slow I'm going. If I did I would use GPS. In any event, the new breaker is supposedly water tight.

So...about the 32 volts?
 

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32VDC is the maximum rating. So it is ok for up to 32V. 12 is less than 32 so it's ok. If it is corroded then replacement is a good idea.
 

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Some older boats had 32-volt systems. My first "big" boat, a 35' gaff-rigged ketch, had such a system.

You can also find 24V, 36V and 48V systems on some boats, inter alia.

Bill
 

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Fuses are not required at least in the USA in starter circuits.
True, but it is a good idea to fuse starting circuits. It is easy to do with the small diesels in sailboats.

If there is a 1/2/both switch both banks can be used for house loads and both should be fused as there is not a dedicated starter circuit.
 
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