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Circuit-breakers, or, blade fuses?

Old 08-29-2014, 04:59 PM
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Default Circuit-breakers, or, blade fuses?

My thought is that a breaker may fail (like trip, then not reset), whereas blade fuses are handy to replace while on the water...unless there was a legitimate reason for it blowing in the first place.

So, which is preferred, blade fuses, or breakers?

[let's exclude glass tubular fuses from the equation...I think they became obsolete about 20+ years ago, but are still generally used for equipment that has an in-line fuse-holder]
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Old 08-29-2014, 05:09 PM
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breakers are way better for most things. I bet 90% of boats on the water don't have spare fuses.
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Old 08-29-2014, 05:34 PM
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Blade fuses come in a more variety in terms of rated amps., I believe. I think the breakers jump like 10A between sizes. Old knowledge, though, so may be off...I haven't compared recently.

So, if you have fuses, you carry spares. Is that too complicated for "90% of boats"?
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Old 08-29-2014, 07:33 PM
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Fuses are cheaper, breakers are more convenient. They both serve their purpose just fine.
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Old 08-29-2014, 10:36 PM
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For new installations, I prefer fuses for devices that have a clearly defined maximum current draw, and breakers for devices that can overheat based on "normal" usage (typically electric motors).

For example: plotters, radios, lighting, and instruments seem suited for fuses. If I blow a fuse on my plotter or my cabin lighting, there's almost certainly an electrical short somewhere.

On the other hand: motor-driven devices like downriggers, pot pullers, windlasses seem better suited for breakers. Those devices can be overloaded through use (or misuse), and a tripped breaker is a heads-up that the device is working too hard, but may be OK to use after a cool-down period. A stereo system could fall into that category, for some very powerful systems.

With that said, my boat was built with breakers for almost everything, and I don't feel any need to change the fixed loads over to fuses.

Last edited by yabbut; 08-30-2014 at 06:59 AM.
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Old 08-30-2014, 03:45 AM
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Originally Posted by smac999 View Post
breakers are way better for most things. I bet 90% of boats on the water don't have spare fuses.
If a pump switch or motor fails; IE fails in the (on) position, if you have a "resetable breaker" how do you turn the unit off?

Mark me down for the (fuse) category, (with some exceptions) we have been using them for years, no issues.
We do use dielectric grease in the fuse holders.
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Old 08-30-2014, 04:42 AM
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Originally Posted by Parker Yacht View Post
If a pump switch or motor fails; IE fails in the (on) position, if you have a "resetable breaker" how do you turn the unit off?

Mark me down for the (fuse) category, (with some exceptions) we have been using them for years, no issues.
We do use dielectric grease in the fuse holders.
I do not follow your first question, can you use an example?
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Old 08-30-2014, 05:42 AM
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Originally Posted by Karl in NY View Post
Blade fuses come in a more variety in terms of rated amps., I believe. I think the breakers jump like 10A between sizes. Old knowledge, though, so may be off...I haven't compared recently.

So, if you have fuses, you carry spares. Is that too complicated for "90% of boats"?
There is little difference in what you can get in breakers vs fuses apart in the very small amp ranges (0-3 amp) - Carling AD series works great. Breakers that can be set to off if needed - some have guards on so you need a thin flat screwdriver to set them to off. But setting them on is like normal switch.

But the future is Digital fuses/switches which are configurable for each device from 0.1 amp to 75 amp. - they are not far away. Check Motobrain as an example. Not perfect but a step in the right direction. You could also check CZONE as another example with blade fuses a backup.
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Old 08-30-2014, 05:48 AM
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Originally Posted by smac999 View Post
breakers are way better for most things. I bet 90% of boats on the water don't have spare fuses.
Even if you don't carry spares, you have many non-critical systems that you can borrow from.
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Old 08-30-2014, 06:59 AM
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Originally Posted by Trayder View Post
I do not follow your first question, can you use an example?
I think he's pointing out that you can turn off a circuit that's stuck "on" by pulling a fuse out of the fuse holder. With the common resettable pushbutton breaker, you can only go from off/tripped to on, not the other way around.
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Old 09-02-2014, 12:59 PM
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Originally Posted by yabbut View Post
I think he's pointing out that you can turn off a circuit that's stuck "on" by pulling a fuse out of the fuse holder. With the common resettable pushbutton breaker, you can only go from off/tripped to on, not the other way around.
Couldn't one just pull the connector to the breaker?
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Old 09-02-2014, 01:24 PM
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Originally Posted by Trayder View Post
Couldn't one just pull the connector to the breaker?
Sure, but that may be easier said than done. Depending on the breaker panel design, it may take time & tools to get to the connectors on the back of the panel. Fuses are more readily accessible, by design.
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Old 09-02-2014, 02:30 PM
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Originally Posted by yabbut View Post
Sure, but that may be easier said than done. Depending on the breaker panel design, it may take time & tools to get to the connectors on the back of the panel. Fuses are more readily accessible, by design.
I guess, but the same can be said about fuse location as well.
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Old 09-02-2014, 03:03 PM
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Yes, of course it's possible to lay out an electrical system so that the fuses in the front of a fuse panel are just as hard to reach as the connectors on the back of an equivalent breaker panel. But that's just a sign of poor design and installation.

In my opinion, for a high-quality installation, fuses will be easier to reach than the innards of a breaker panel (that serves the same function as the fuse panel).

In the end, we all have choices on how to lay out our boats' electrical systems. If you think breakers or fuses (or some combination of the two) are the best solution, use what you want. Other people will have different solutions that work better for them.
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Old 09-02-2014, 03:44 PM
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Originally Posted by yabbut View Post
For new installations, I prefer fuses for devices that have a clearly defined maximum current draw, and breakers for devices that can overheat based on "normal" usage (typically electric motors).

For example: plotters, radios, lighting, and instruments seem suited for fuses. If I blow a fuse on my plotter or my cabin lighting, there's almost certainly an electrical short somewhere.

On the other hand: motor-driven devices like downriggers, pot pullers, windlasses seem better suited for breakers. Those devices can be overloaded through use (or misuse), and a tripped breaker is a heads-up that the device is working too hard, but may be OK to use after a cool-down period. A stereo system could fall into that category, for some very powerful systems.

With that said, my boat was built with breakers for almost everything, and I don't feel any need to change the fixed loads over to fuses.
Excellent advice.!
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Old 09-02-2014, 04:28 PM
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Originally Posted by Karl in NY View Post
My thought is that a breaker may fail (like trip, then not reset), whereas blade fuses are handy to replace while on the water...unless there was a legitimate reason for it blowing in the first place.

So, which is preferred, blade fuses, or breakers?

[let's exclude glass tubular fuses from the equation...I think they became obsolete about 20+ years ago, but are still generally used for equipment that has an in-line fuse-holder]
It depends on what you're connecting to the circuit, and the purpose of the protection. As to the latter, I've read you should have protection (fuse or breaker), within (I think) 6" of the connection to an upstream busbar or equivalent (e.g. the +chain in a panel). I've read this is nominally to protect the wiring (from melting and/or causing a fire in the event of severe overloading or a short).

Many devices (e.g., radios, MFDs, stereo stuff, etc.) will come with inline fuses close to the power inlet of the device. These are to protect the device, not the upstream wire. When you wire up a new device, I've read you still need to have the source side protection for the wire in addition to the device side fuse.

Fuses come in finer-grained increments than breakers, so going with a fused switch panel I've read gives you the option of eliminating the inline fuse next to the device, and using the same fuse rating at the switch (which is dedicated to that device).

I have a small CC, and started off by buying some Weatherdeck panels with breakers before I really had planned out what I was doing. I've read breakers are generally better for protecting wiring. One broad example noted in earlier posts is for loads imposed by overtaxed electric motors. Another is for protecting the wire to a downstream panel (i.e., a breaker or switch supplying current to a panel which itself will have multiple circuits to devices.

I subsequently bought an 8-place fused Weatherdeck to handle all the electronics so to be able to remove all their inline fuses. I've read this makes fuse replacement possible at the panel rather than rooting around under the console.

I've read that one should use larger dedicated inline breakers near the upstream wiring connection for stuff like electric trolling motors.

So a good way of thinking about this is it being like an upside-down tree, with the power source at the top. One needs wire protection at the top. One needs wire protection just after every branch, even if the branch only has one leaf. Protection just before the leaf/device is common for stuff like radios and such, but I've read you can place that just after the leaf-dedicated branch with an appropriately size fuse (or breaker if it happens to be available in the appropriate size).

DISCLAIMER: These are my unverified speculative opinions, and are not intended for use in actual wiring, which you should do at your own risk or the risk of other indemnifying entities. Any actual wiring performed by readers of this post, by the act alone, controverts potential claim of liability based on this post.

In other words, base your design on what you learn from professionals or professionally published books. I disclaim any responsibility for mistakes you might make based on this post. Don't set fire to your boat, damage its systems or components.

Tight circuits...

-ks
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