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Old 30-07-2017, 07:40   #1
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Breaker Switches vs Fuses

This may be the dumbest question you read all day...

What's the difference between a breaker switch, and a fuse panel switch?

I'm assuming that a breaker switch is an all-in-one switch, whereas a fuse panel switch has a separate rocker switch and fuse.
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Old 30-07-2017, 07:51   #2
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Re: Breaker Switches vs Fuses

They are both a safety point in the wire. The weakest point in the system, designed to "fail" if something goes wrong.
In general basic terms. Fuses are cheaper and easier to set up, but need to be replaced every time they trip.
Breakers cost more and take a little more time, but generally are more aesthetic because of that. They also can be reset once tripped.
Both need to be wired properly with the proper sized fuse or breaker to protect your wire and appliances.
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Old 30-07-2017, 08:04   #3
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Re: Breaker Switches vs Fuses

Is there a general rule of which systems should be on breakers and which can be on fuses?
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Old 30-07-2017, 08:11   #4
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Re: Breaker Switches vs Fuses

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Originally Posted by TooCoys View Post
Is there a general rule of which systems should be on breakers and which can be on fuses?

There is no general rule. But it's a good idea to have critical systems on a breaker. Sometime you will run out of or cannot find the right fuse. So try to guess which systems you never want to be without for lack of a fuse. Put those on properly sized breakers. Some key DC system examples:

Bilge pump
Bilge blower
Windlass
VHF radio
Water maker

You may think of others.
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Old 30-07-2017, 08:18   #5
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Re: Breaker Switches vs Fuses

This is certainly NOT a dumb question! It is something that everyone needs to know and understand and everyone has to start out not knowing it to start.

The rule would be: put in switches on a circuit when you don't always want it on and so want to decide when to separately power that device/circuit. Taking out a fuse to cut the power is very inconvenient if you want to do that on a regular basis.

Some things like that may be instruments, propane systems, radios, etc. You may want to turn them off to do maintenance or to save power or just turn them on and off when you want.

You can have a switch and fuse panel where the switch is next to the fuse underneath a cap on the face of the panel. It is easier to replace the fuse that way but the panel is more complicated, therefore more expensive.

Breakers so both but are more expensive and take more room in the back of the panel.

Both of them have the drawback that all the circuit wiring you want on them has to be pulled to the panel location. That can be a lot of work if not already done. Not so bad on less complicated, smaller, boats. Mose bigger boats already have panels, and nowadays they are usually breaker panels.

You don't have to run every circuit to the panel. You might wire bilge pumps directly to the main battery switch, or direct to the battery. Same for devices that have a separate on/off switch, like radios, lights, etc. You have to fuse those at the point they connect to bigger wires or switches (not at the device but you can have both). What a fuse and/or breaker does is prevent the wire from melting from shorting out along its path so you want to fuse it where the power starts, not ends.

Fuse and breaker sizing is therefore dependent on the wire size. Bilge pumps should have bigger wires so they can have bigger fuses. The fuse size also has to be able to carry the power the device needs to run, such as bilge pumps. So you have to pull larger wires for high draw devices and then fuse (or put on a breaker) them appropriately.
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Old 30-07-2017, 08:53   #6
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Re: Breaker Switches vs Fuses

If you have fuses you really should consider upgrading to circuit breakers! Try replacing fuses in heavy going to restore a critical system!
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Old 30-07-2017, 09:04   #7
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Re: Breaker Switches vs Fuses

The plus on breakers are they are right at distribution point and there isn't any unprotected wire
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Old 30-07-2017, 10:04   #8
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Re: Breaker Switches vs Fuses

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Originally Posted by lesterbutch View Post
If you have fuses you really should consider upgrading to circuit breakers! Try replacing fuses in heavy going to restore a critical system!


I don't know what I have right now. I'm planning to rip everything out of this 1967 Chris Craft and start over so that I KNOW what is where and how it's wired. Right now I only know of about 8 fuses on the whole boat.
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Old 30-07-2017, 10:09   #9
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Re: Breaker Switches vs Fuses

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If you have fuses you really should consider upgrading to circuit breakers! Try replacing fuses in heavy going to restore a critical system!
If a fuse blows there is often a reason that needs to be investigated. They aren't there just to inconvenience you and get reset. Building planes we are moving more toward automotive style fuses that usually hold up quite well as designed. Replacements are cheap and could easily be carried in a small, waterproof, container.
Also, the more you cycle a breaker the weaker they can become. Hence, again on planes, we have master switches and don't use the breakers unless necessary to shut off circuits.
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Old 30-07-2017, 10:20   #10
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Re: Breaker Switches vs Fuses

Some sensitive electronics/electrical equipment need the protection offered only by a fuse of the precise value, in addition to the circuit breaker which protects and controls the entire circuit.
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Old 30-07-2017, 10:26   #11
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Re: Breaker Switches vs Fuses

Circuit breakers do the same job as a fuse and a switch, but they have the advantage of fewer connections (important with low voltage in the marine environment) and the ability to instantly reset.

They are the only real option these days.

However, they do have a couple of drawbacks:

1. The cheaper breakers when exposed to large current cannot be reset. They essentially destroy themselves interrupting the circuit.

2. DC switching can produce some arcing. This gradually destroys the CB and many models do not not have a great life. Try and choose quality products and if possible use the CB only as a switch when the device is not drawing any current. The best defence is to have CBs that are easily replaced. Multiple CB are also a help. Each one is switched less often and if one fails there is less disruption to important systems. Modern boats often have too few independent circuits in my view.
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Old 30-07-2017, 11:13   #12
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Re: Breaker Switches vs Fuses

Quote:
Originally Posted by transmitterdan View Post
There is no general rule. But it's a good idea to have critical systems on a breaker. Sometime you will run out of or cannot find the right fuse. So try to guess which systems you never want to be without for lack of a fuse. Put those on properly sized breakers. Some key DC system examples:

Bilge pump
Bilge blower
Windlass
VHF radio
Water maker

You may think of others.
And a fuse may blow at the most inopportune time. eg. bad weather. I don't however subscribe to using a breaker as a switch.
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Old 30-07-2017, 11:18   #13
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Re: Breaker Switches vs Fuses

Once you get up to large currents it is much better and cheaper to use fuses for safety.

Choosing the right breakers can be complex, most have some built-in delays before tripping.

Over 40-60A they also get very expensive.
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Old 30-07-2017, 11:20   #14
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Re: Breaker Switches vs Fuses

Quote:
Originally Posted by TooCoys View Post
What's the difference between a breaker switch, and a fuse panel switch?

I'm assuming that a breaker switch is an all-in-one switch, whereas a fuse panel switch has a separate rocker switch and fuse.
Quote:
Originally Posted by noelex 77 View Post
Circuit breakers do the same job as a fuse and a switch, but they have the advantage of fewer connections (important with low voltage in the marine environment) and the ability to instantly reset.

Just a quick post to note there's a difference between a fuse, a breaker, and a switch.

The first two are about circuit/equipment protection, and last is mostly just about user-controlled ON/OFF.

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Old 30-07-2017, 11:38   #15
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Re: Breaker Switches vs Fuses

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Originally Posted by john61ct View Post
Once you get up to large currents it is much better and cheaper to use fuses for safety.

Choosing the right breakers can be complex, most have some built-in delays before tripping.

Over 40-60A they also get very expensive.
Time delay breakers are for high starting currents, generally motors.
A fuse would have to be rated at that draw thus making them not effective as long term over current situations. Most of use don't have high inductive loads. A windless is probably about it.
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