How many circuit breakers/fuses to I need?

LadyAnya

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Hello, everyone. I am re-wiring my '88 Sunrunner because it was a mess. I found a breaker box under the dash and it has about 6 circuit breakers and there is also a panel with ground bus and +12v bus with glass fuses on it.

My question is, how many breakers/fuses do I need? Does it depend on the number of accessories? I will take a picture later to better show what I am talking about.
 

rwidman

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Re: How many circuit breakers/fuses to I need?

Hello, everyone. I am re-wiring my '88 Sunrunner because it was a mess. I found a breaker box under the dash and it has about 6 circuit breakers and there is also a panel with ground bus and +12v bus with glass fuses on it.

My question is, how many breakers/fuses do I need? Does it depend on the number of accessories? I will take a picture later to better show what I am talking about.

You need circuit protection for each circuit. Ten circuits - ten breakers or fuses. Fifteen circuits - fifteen breakers or fuses. It never hurts to install spares in case you decide to add some accessory sometime in the future.

Don't forget that you must have circuit protection for the conductor leading from the battery or switch to the breaker or fuse panel. This protection should be rated for the size of the conductor and installed within seven inches of the source of power.
 

LadyAnya

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Re: How many circuit breakers/fuses to I need?

"Don't forget that you must have circuit protection for the conductor leading from the battery or switch to the breaker or fuse panel. This protection should be rated for the size of the conductor and installed within seven inches of the source of power."

What does a circuit protection look like? What is an example of a conductor?

Thanks
 

dwco5051

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Re: How many circuit breakers/fuses to I need?

"Don't forget that you must have circuit protection for the conductor leading from the battery or switch to the breaker or fuse panel. This protection should be rated for the size of the conductor and installed within seven inches of the source of power."

What does a circuit protection look like? What is an example of a conductor?

Thanks

A conductor is the proper name for a wire that carrys a load from the source to where the power is used. It "conducts" the electric power from one place to another, thus the name.

Circut protection is normally either a fuse or a circut breaker.
 

EricJRW

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Re: How many circuit breakers/fuses to I need?

Just thought I'd chime in, as I did this to my boat too.

Basically you most certainly want a new circuit (with overload protection) for every old circuit you are redoing.

In my case (see picture), my old fuse block had six fuses, so my new one does too. Yeah, it would have been nice to have some spares, but there are ways around that. For example, my fish-finder and radio use in-line fuses (so they are not tied to the block - you can see one in the upper left corner of the photo).

I keep looking for a photo of the before picture, as it was a real mess. If I find it, I'll post it.
 

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LadyAnya

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Re: How many circuit breakers/fuses to I need?

What size breaker would I need to provide adeqaute protection?
 

EricJRW

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Re: How many circuit breakers/fuses to I need?

If you are redoing, I would replace what's there with the same size fuses/breakers. The rating of the fuse/breaker should be on it. The rating of breakers and fuses are expressed in amps, basically how much current can pass through the fuse/breaker before it blows. Each application is different, but the size of the wire (conductor) is the biggest factor. You don't want to use a fuse/breaker larger than the max amount of current the wire can handle. That being said, it is quite common to use a fuse/breaker smaller than what the wire can handle, but slightly larger than the maximum current draw of the device. This way, if there is a problem, e.g a short circuit or the device starts drawing too much current, the fuse/breaker will blow before the wiring is damaged.

Without knowing more information, it's impossible to say what size fuses/breakers you need. Just keep in mind that if a fuse blows, it needs to be replaced, so it's good to carry spares. With breakers, they come in two varieties: manual and automatic. If a manual breaker pops, you must manually reset it. With automatic breakers, they will automatically reset... But if the problem is not fixed, they will pop again (and this cycle will repeat until the problem is fixed).
 

Silvertip

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Re: How many circuit breakers/fuses to I need?

Breaker to protect what? Circuit breakers are sized for the circuit you are protecting. Installing a 10 amp breaker on a wire that can only carry 5 amps before going up in smoke would be a mistake. The wire would burn up before the breaker opened. You also install breakers or fuses sized for the current draw on that circuit. A bilge pump may draw 4 - 5 amps for example but may be wired with 14 or 16 gauge wire. You would not put a 15 amp breaker or fuse on that 14 gauge circuit or a 10 amp fuse on the 16 gauge circuit even though the wire can safely handle that current. You want that fuse or breaker to open at slightly over the current draw of the bilge pump. So perhaps a 7.5 amp fuse would be in order. My suggestion for you is to visit the local library and check out a books titled "Low Voltage Wiring Basics" or some similar title.
 

rwidman

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Re: How many circuit breakers/fuses to I need?

"Don't forget that you must have circuit protection for the conductor leading from the battery or switch to the breaker or fuse panel. This protection should be rated for the size of the conductor and installed within seven inches of the source of power."

What does a circuit protection look like? What is an example of a conductor?

Thanks

LadyAnya,

Please don't take this the wrong way, but if you're not familiar with the terms "conductor" and "circuit protection", in my opinion, you should not be thinking about rewiring a boat yourself.

Boat electrical work is not "rocket science", but it is a trade that takes considerable study. You will need to design a wiring system, then install it using marine materials and wiring practices. It's nothing to be ashamed of, not knowing the trade, you are probably really good at something else. You will not learn everything you need to know by asking questions on a web forum.

If you don't feel your boat is worth the cost of paying a pro to rewire it or just repair what you have, ask yourself what your family's safety is worth.

That improperly wired boat could leave you stranded on the water, or worse, burst into flame.

Think about it.
 

EricJRW

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Re: How many circuit breakers/fuses to I need?

Here's my before picture.

FYI, all my new crimp connectors are also soldered.
 

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LadyAnya

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Re: How many circuit breakers/fuses to I need?

Thanks for the advice. I just wanted to be on the same page as everyone with terms and other things. I feel capable enough to design a properly wired system. The more I read and research the more confident I become.

My wiring was worse than what your picture shows.
 

bruceb58

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Re: How many circuit breakers/fuses to I need?

I would like to comment on Eric's fuse panel.

1) The feed wire looks way too small. Should be sized large enough to deliver the max load of all circuits.
2) There are no labels per fuse or what the value the fuses should be.
3) Wires are all over the place.
4) Looks like there is no fuse in the feed from the battery charger.
5) Looks like there are black colored wires connected to the fuses going to loads. Never use black colored wires for anything but ground.


My suggestion to the original poster is to buy a fuse panel that already have labels or has a place to put labels. Don't use a fuse panel which uses round glass fuses held by clips. Use the newer style blade fuses.

Also, use a good crimp connector with the proper crimp tool and you don't need to solder.
 

EricJRW

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Re: How many circuit breakers/fuses to I need?

I would like to comment on Eric's fuse panel.

1) The feed wire looks way too small. Should be sized large enough to deliver the max load of all circuits.
2) There are no labels per fuse or what the value the fuses should be.
3) Wires are all over the place.
4) Looks like there is no fuse in the feed from the battery charger.
5) Looks like there are black colored wires connected to the fuses going to loads. Never use black colored wires for anything but ground.


My suggestion to the original poster is to buy a fuse panel that already have labels or has a place to put labels. Don't use a fuse panel which uses round glass fuses held by clips. Use the newer style blade fuses.

Also, use a good crimp connector with the proper crimp tool and you don't need to solder.

Yeah, it's far from ideal, but it's better than when I got it. :)

Just to let you know, I am working on things:

1) One of these days I'll add everything up and size correctly, but for now I know it's highly unlikely that everything will be on at the same time. My goal is to make sure I have a fuse back at the battery that will protect me from this situation. This is something I do need to double-check, so thanks for the reminder.

2) The block is not labeled, but I did make a table when I replaced the old block (it's in my log book). I think I'll make a copy and tack it up next to the block. Thanks for the idea.

3) I still need to re-do my two rocker switches (live well and lights - see attached). When I'm done with that everything will be zip-tied. I was going to use cable organizer (that tubular stuff), but decided it might trap moisture.

4) Battery charger is fused internally. I'm thinking external would be overkill. Am I wrong?

5) Yeah... Again, inherited problem. I have a roll of red electrical tape that I plan to use to mark those wires. Someday they might get replaced, but I have to pick my battles as I go.

Thanks for taking the time to look that over. You gave me some good things to think about (and I'm sure it will help the OP too).
 

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bruceb58

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Re: How many circuit breakers/fuses to I need?

2) The block is not labeled, but I did make a table when I replaced the old block (it's in my log book). I think I'll make a copy and tack it up next to the block. Thanks for the idea.
Those little Brother labeling machines are really good for something like this. You will find tons of uses for the machine besides your boat. My name/phone number gets put on tons of stuff now.
 

EricJRW

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Re: How many circuit breakers/fuses to I need?

Those little Brother labeling machines are really good for something like this. You will find tons of uses for the machine besides your boat. My name/phone number gets put on tons of stuff now.

Good idea... I actually own two of those.
 

rwidman

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Re: How many circuit breakers/fuses to I need?

4) Battery charger is fused internally. I'm thinking external would be overkill. Am I wrong?

Yes you are wrong. The positive wire connecting the battery charger to the battery is powered (when in the charging mode) at both ends. If it becones shorted, the internal fuse in the charger may blow, but there's still an unprotected connection to the battery. The wire could melt and catch fire.

Like everything else, it should be protected within seven inches of the source (in this case the battery end and the charger end). If the output (DC) circuit of the charger has a fuse or circuit breaker, this will take care of the charger end of the circuit.

BTW: ABYC now specifies yellow as DC negative. Yellow you say? Why yellow?

On a boat with 120 volt AC shore power, the ground is green, the neutral is white, and the "hot" conductor is usually black, just like in your home or business. Anyone working on a boat who mistakes the 120 volt AC black hot wire for a 12 volt DC negative or ground wire is in for a big surprise. :eek:

I'm not sure how long ago this change was made. My year 2000 boat and my previous boat, a 2003 used black for DC negative. A slip neighbor's more recent boat uses yellow for DC ground.
 

LadyAnya

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Re: How many circuit breakers/fuses to I need?

I was planning on upgrading the panel to the blade type.

Do I need breakers and fuses after the conductor or just a breaker from the conductor to the fuse panel will suffice?
 

rwidman

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Re: How many circuit breakers/fuses to I need?

I was planning on upgrading the panel to the blade type.

Do I need breakers and fuses after the conductor or just a breaker from the conductor to the fuse panel will suffice?

LadyAnya,

This is from one of your previous posts:

"I feel capable enough to design a properly wired system. The more I read and research the more confident I become."

It's clear from your question that you don't understand the purpose of fuses or circuit breakers. Without this understanding, you cannot design a properly wired boat electrical system.

If you insist on rewiring your boat yourself, at least buy some books on the subject and study them until you think you understand.
 

LadyAnya

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Re: How many circuit breakers/fuses to I need?

I was planning on picking up a book this week, however I would also appreciate answers and guidance.
 
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