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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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Old 10-25-2013
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Fuse/Breaker Confusion

I'm planning to rewire a boat and I'm confused.

I'm getting rid of the jumble of outdated wiring. I'm starting fresh with a Blue Sea 8084 panel. Like here:

Blue Sea Systems 8084 Panel 16-12VDC/8-120VAC w/Main

As you can easily see when you mouse over the pic to magnify the photo of the panel, Blue Sea sets it up for some standard uses. Looking at a couple of examples we find a 15A breaker for spreader lights and another 15A breaker for an anchor light. Ok.

My problem is that spreader lights are not going to call for (per manufacturer's recommendations) 15A breakers. They are going to suggest a much smaller breaker/fuse. Same with the anchor light.

Main Cabin Lights is another example. Maybe I have half a dozen cabin lights, each needing a 1 or 2 amp fuse/breaker.

Can someone please explain to me why I would dedicate a 15A breaker to each of these?

Thanks!!!
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Old 10-25-2013
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Re: Fuse/Breaker Confusion

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Originally Posted by Sailinstuff View Post
I'm planning to rewire a boat and I'm confused.

I'm getting rid of the jumble of outdated wiring. I'm starting fresh with a Blue Sea 8084 panel. Like here:

Blue Sea Systems 8084 Panel 16-12VDC/8-120VAC w/Main

As you can easily see when you mouse over the pic to magnify the photo of the panel, Blue Sea sets it up for some standard uses. Looking at a couple of examples we find a 15A breaker for spreader lights and another 15A breaker for an anchor light. Ok.

My problem is that spreader lights are not going to call for (per manufacturer's recommendations) 15A breakers. They are going to suggest a much smaller breaker/fuse. Same with the anchor light.

Main Cabin Lights is another example. Maybe I have half a dozen cabin lights, each needing a 1 or 2 amp fuse/breaker.

Can someone please explain to me why I would dedicate a 15A breaker to each of these?

Thanks!!!
The breakers are there to protect the WIRE. You will not be using smaller than 14GA or 16GA (16GA is the smallest allowed under ABYC standards for most situations) for house wiring so 15A breakers are fine.... They also don't fill all the slots in the panels so you can add higher load breakers for devices like macerators etc. that draw more than 15A..

You might consider the Blue Sea 8408 as it adds digital ammeter/voltmeter and digital AC volts as well as 18 DC positions and 6 AC.. It is a great panel for not a heck of a lot more than 8084. By losing that middle analog display you gain 3 more DC breakers which are far more valuable than analog volts or amps........ Just a thought....
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Re: Fuse/Breaker Confusion

Fuse size has nothing to do with the load. It has to do with the wire size. A 15A fuse or breaker protects a #14 wire. Who cares how much the load draws, as long as it's less than the capacity of the wire, which for #14 is 15 A. Exceed that, and the breaker trips or the fuse blows.
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Re: Fuse/Breaker Confusion

Maine and I posted simultaneously.
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Re: Fuse/Breaker Confusion

Thanks.

If you have the time, would you explain to me what is wrong with running all three types of light to one breaker?
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Re: Fuse/Breaker Confusion

Nothing wrong with it, but if they are on one breaker you won't be able to isolate each separately. This may not be a big deal. Up to you.
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Re: Fuse/Breaker Confusion

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Originally Posted by Sailinstuff View Post
Thanks.

If you have the time, would you explain to me what is wrong with running all three types of light to one breaker?
Nothing as long as the wire is sized properly and the circuit is wired parallel not series wired....
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Re: Fuse/Breaker Confusion

Thanks. I did not envision wiring in series. I was asking about parallel wiring. But that does inspire another question, if you will:

What about wiring all the cabin lights, clock, stereo, etc., to a dual bus with that bus wired to one panel breaker?
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