Breaker Switches vs Fuses

[David M]

Bottom line, use breakers over fuses if you can afford the price difference.

[Cadence]

Originally Posted by mitiempo

The 10,000 cycles that an A series Blue Seas breaker is rated for translates to almost 14 years @ twice per day. I don't think is is much of an issue really.

You are probably right. Maybe I suffer from paranoia. It only takes one welded set of breaker points to burn someone down to the waterline. Switches are cheap. JMHO

[rwidman]

Originally Posted by David M

Bottom line, use breakers over fuses if you can afford the price difference.

No.

You will end up with a combination of fuses and circuit breakers. For example, you might have a 15 or 20 amp breaker supplying power to the "electronics". This will be a fuse panel with a 7.5 amp fuse for your MFD, a 3 amp fuse for your depth sounder, a 1 amp fuse for your GPS antenna, a 10 amp fuse for your VHF and a 3 amp fuse for your AIS.

You can't find marine breakers for most of those values and often, the manufacturer will specify a fast blow fuse.

[rwidman]

Originally Posted by TooCoys

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.

No offence intended, but if you're asking questions like this one, you aren't ready to rewire a boat.

My purpose is not to insult you, but to protect you and your family and friends.

[john61ct]

Originally Posted by David M

Bottom line, use breakers over fuses if you can afford the price difference.

Did you even read the thread?

[Lake-Effect]

Originally Posted by Cadence

You are probably right. Maybe I suffer from paranoia. It only takes one welded set of breaker points to burn someone down to the waterline. Switches are cheap. JMHO

I mentioned this the last time we discussed marine breakers used as switches: I believe that regular manual operation is better for such a breaker than just treating it as a purely protective device. A marine switch or breaker that isn't cycled once in a while could develop the tendancy to stick in the on position.

Also, when the breaker manufacturer quotes the lifespan of manual switched cycles (eg 10k), that's at near rated load. I expect that if your actual load is considerably less than the breaker rated load, the breaker will last longer.

[sv.antea]

A minor point. A bilge pump is best served by a fuse and an on-off-momentary on switch.
The fuse needs to be a slow blow and rated as per manufacturer recommendation for a given pump. I assume the wiring would be heavy enough to keep voltage drop down, not just adequate to the expected draw. So when the bilge pump sucks in a piece of trash or the impeller winds up some hair, the fuse blows and the pump can be put back online after the impeller was cleared, rather than burning up.

[mitiempo]

Originally Posted by sv.antea

A minor point. A bilge pump is best served by a fuse and an on-off-momentary on switch.
The fuse needs to be a slow blow and rated as per manufacturer recommendation for a given pump. I assume the wiring would be heavy enough to keep voltage drop down, not just adequate to the expected draw. So when the bilge pump sucks in a piece of trash or the impeller winds up some hair, the fuse blows and the pump can be put back online after the impeller was cleared, rather than burning up.

I do not think the manual switch for a bilge pump should be momentary. I agree with Steve D'Antonio that when the bilge is filling and the float switch has given up there are better things to do than keep your finger on a switch - like finding and fixing the leak.

It is no different than boiling water on the stove - make sure the water doesn't boil away leaving the pot dry.

[noelex 77]

Originally Posted by sv.antea

A minor point. A bilge pump is best served by a fuse and an on-off-momentary on switch.
The fuse needs to be a slow blow and rated as per manufacturer recommendation for a given pump.

I am curious why you would advocate a fuse rather than a circuit breaker in this application.

A fuse cannot be quickly reset. There is also some concern with a fuse that suitable replacement may not be found, especially if multiple fuses are needed. Bilge pumps are most likely to activate circuit protection if they become clogged with debris and this may occur several times in an emergency situation.

Providing adequate circuit protection for electric motors can be difficult. The high inrush currents make appropriate sizing problematic. If you are concerned that the fast response of a circuit breaker is an issue, then alternative protection curves that give a slower response are available. In practice most people do not bother, as nuisance trips are rare. If you are concerned about this possibility increasing the size of the supply wire will have the advantage that the circuit breaker rating can be on the higher side and there is side benefit of reduced voltage loss which can significantly improve the pumping capacity. Centrifugal pumps are very sensitive to voltage drop.

[noelex 77]

Originally Posted by Lake-Effect

A marine switch or breaker that isn't cycled once in a while could develop the tendancy to stick in the on position.

Yes, a good observation. Slight corrosion on the contact points can be a problem and periodic operation helps keep the contact points clean.

The main problem that leads to failure of the circuit breaker is that when switched a small spark is produced across the contact points. This is particularly a problem switching DC, as the voltage does not drop to 0v as it does with the AC (alternating current) cycle. The 0v point in AC operation tends to rapidly extinguish any sparking.

The sparking produces some pitting of the surface of the contacts and gradually destroys the surface. It will produce higher resistance before the breaker stops working completely.

This is not a great concern with good quality circuit breakers (and this includes the Blue Seas models), but can be a problem with some of the less well made circuit breakers, especially with the modern trend of fitting only a small number of breakers. Each breaker will be switched more often under higher load and of course failure of one breaker will take down multiple systems. In these cases it is good practice, where possible, to try and reduce the load before switching the breaker. As you point out, periodic cycling (preferably under no load) for the less used breakers is probably good preventative maintenance as well.

It is also good practice to group the ciruit breakers (and have enough) so that falure of one circuit (and this may be due to other problems not just the circiut breaker itself) will not take out, for example, all the navigational equipment, or all the navigation lights.

[sv.antea]

OK Mitiempo, you are right of course. Always thought the commercially available bilge pump switch panels were sily. As of day before yesterday, I realise the 'momentary' manual has some merit in some circumstances. I was doing a major work on friends boat that required removing the batteries to gain access to the aft end of the engine. While fixing to quit for the day, my friend pointed out that there was some water in the bilge. So I hooked up one of the batteries. He flipped the switch, a on-off-on toggle I installed months before, the bilge pump came on and the water level was going down. I know. I should have waited to see if it stopped. Good thing the only damage I found the next morning was to the pump.
And Noelex77, the gist of my wordy contribution was that a slow blow fuse with the right amperage will protect the pump. Circuit breake would do the same and more conveniently, if you could buy a circuit breaker with the rating of, say 6.5A. Bilge pumps specs call for pretty specific fuse amperages including half amp steps and I assume it is for that reason. The fuse needs to handle the onrush of starting, but blow if the pump rotor gets jammed.

[sstuller]

The converter in my RV has breakers on the AC side and fuses on the DC side. Breakers for AC and fuses for DC is a simple solution. Thanks.

[TooCoys]

Originally Posted by rwidman

Unless there are issues, I would advise against that. It's a lot of work, especially for a beginner and in the end, you have the same boat but you've put a lot of time and money into a job that didn't need to be done.

If you can't figure out where everything is and how it's wired, it would be less costly to hire a qualified marine electrician to show you this. Far less costly.

There aren't any issues that I've noticed, but there are some things that I'd like to add.

For instance there is no on board stereo. I'm perfectly fine wiring my own audio system, but there are no more fuses on the 50 year old fuse panel to wire it to. I would have to add a secondary fuse panel somewhere.

There's also no genset, or battery bank. The only DC power that is supplied is from the two starter batteries, and I'm not comfortable leaving DC powered items running when the engines aren't running. I need to add a battery bank even in its smallest form so that I'm not dependent on the starter batteries.

And my boat is 50 years old, with original 50 year old AC and DC wiring. I would hate to be out on the water and have something simple fail because a 50 year old wire decided to crack.

[TooCoys]

Originally Posted by rwidman

The OP never said why he wanted to know the difference, but as a practical matter, the boat manufacturer usually installs the appropriate device.

Because I have seen DC panels that have the switches, with the Buss fuses on the side, and I have seen the breaker switch panels like what was on my sail boat.

Breaker switches are a lot more expensive, than toggle switches and buss fuses.

[TooCoys]

Originally Posted by Lake-Effect

So before you go whole hog with a rewire, book a pro for a couple of hours to review your boat's electrics and answer your questions. There may be nothing seriously wrong with your boat.

That's a good idea.