Fuses versus circuit breakers

[capta]

I've always used circuit breakers for load lines. All my equipment manufacturers mention only fuses as protection for incoming lines like solar and wind charging.
Would a circuit breaker do just as well as a fuse for incoming power from my solar and wind chargers, my battery chargers and the engine alternator, or are they designed for draw rather that push loads?
The reason I ask is that I'm having trouble finding fuse holders that I can mount on a wall down here.
I hate the thought of putting 12 gauge inline fuse holders in a 10 gauge line, even if they are rated for 30 amps, never mind how tacky it would look..

 

[woodster]

get a blue sea fuse block for those plug in type fuses like in the car they com in 6 and 12 slot/circuit boards and you just add what you need.... like this http://shop.sailboatowners.com/search.php?brand=sailboat&kw=blue+seas+fuse+blocks

 

[CloudDiver]

Fuses are just a more economical choice. Circuit breakers are more expensive (by far) but give the convenience of resetting when tripped quickly rather than fishing out a new fuse and replacing.
Since my boat is much smaller I can get away with fuses on just about everything. On a bigger boat like yours I'd have my main panel as all breakers, pretty much the primary circuit protection. I think what you are getting at is if you should use fuses or breakers when protecting components individually when they share the same load as other components... Like your auto pilot may be on a 15amp breaker protected circuit, but the manufacturer recommends a 3 amp in line fuse close to the component. I would say its always money well spent to go with the breaker. For example, on my little C-22 I could put a 30 amp in-line fuse near the house battery, but its in a place that is a pain to reach so a circuit breaker adds the convenience of a quick visual to see if its tripped and an even quicker switch flip to re-set it.
When ever I use blade fuses I buy the LED ones, they glow only when BLOWN.

 

[Ken Cross]

Actually I have an opposing opinion. For your application, circuit breakers should be fine.

For low current protection, fuses are much better because they can be made to work at low currents like 1/10 amp. Circuit breakers like fuses are thermal in nature where a high current will trip them quickly, but a slightly over current will take a while to trip them. For solar and wind chargers you are really trying to protect the wiring from creating fire. Circuit breakers are just fine for that.

If you are trying to protect a delicate circuit board the fuse is much better. In the old days of vacuum tubes slow blow fuses were pretty common because of the large influx of current caused by the internal heaters in the tubes when they are first turned on. We don't use slow blow often these days.

Ken

 

[capta]

I guess I wasn't very clear. I need circuit protection for battery charging applications. A solar array for both house and engine start batteries @ 30 amps each. A windgen, for both house and engine start batteries @ 30 amps each. A 40 amp 110volt battery charger appropriately protected for both house and engine start batteries. An 80 amp 110 volt battery charger appropriately protected for both house and engine start batteries and an alternator from the ME.
All of these are incoming power, not load. I don't think inline fuses will do the job on the heavier circuits and I think having a bunch of inline fuse holders dangling from the wires would look pretty cheesy. The high power single ANL fuse holders don't seem to go low enough and those set ups are every bit as expensive as breakers, if not more. The fuse panels for the glass fuses, even though the fuses go to 30 amps or more, only seem to be designed for 20 amp circuits.
So the question remains, will circuit breakers work for incoming power as well as they do for loads?

 

[Ken Cross]

Yes circuit breakers should be fine. Having said that fuses will certainly work, but certainly not the cheap inline holders you alluded to. If you were to go with fuses, you would need to use appropriate ones.

Ken

 

[Maine Sail]

If these are directly wired to a bank or its bus then the breaker should have a minimum AIC rating of 5000A. If the bank is really large there are no marine duty breakers that carry the proper AIC rating and you run the risk of an unsafe failure.. Generally the fuses used for direct battery connection are ANL or MRBF in these sizes...

 

[Charles Erwin]

The fuse at the battery end of the wire protects the wire going to the device because that wire can also conduct current in the other direction.

To illustrate the point - ask yourself what would happen if the wire came loose at the device end (at the wind charger or at alternator) and shorted to ground at the device end? The feed now is from the battery - not toward the battery. If you think about it that way you will see that the threat is the several thousand amps originating from the battery ending up at the (now shorted) 'device' end of the wire. This is why every cable connected to the battery needs overcurrent protection near the battery and that means a fuse with AIC appropriate values. No breaker (within an acceptable price range) will reliably handle this problem.

Thus fuse the battery end.

Charles

 

[Stu Jackson]

.............several thousand amps originating from the battery ending up at the (now shorted) 'device' end of the wire. This is why every cable connected to the battery needs overcurrent protection near the battery and that means a fuse with AIC appropriate values. No breaker (within an acceptable price range) will reliably handle this problem.

Thus fuse the battery end.

Charles is right. So is, always, Maine Sail.

Capta, what's so hard? I KNOW you read a lot of different boating forums, this stuff is kinda basic.

 

[capta]

Charles is right. So is, always, Maine Sail.

Capta, what's so hard? I KNOW you read a lot of different boating forums, this stuff is kinda basic.

Availability where I am makes it difficult to find the correct bits and pieces. Therefore trying to come up with something that will do the job with what's available.

 

[Charles Erwin]

Hey any fuse, anywhere, is better than no fuse. The closer to the battery the better

Charles

 

[capta]

If these are directly wired to a bank or its bus then the breaker should have a minimum AIC rating of 5000A. If the bank is really large there are no marine duty breakers that carry the proper AIC rating and you run the risk of an unsafe failure.. Generally the fuses used for direct battery connection are ANL or MRBF in these sizes...

These charging circuits are all after an ANL, on a bus bar. I am just trying to find a way to stay with the manufacturers' fusing recommendations for each leg of each circuit that is affordable and not too unsightly. Only one wire (the 2/0) goes to the battery directly from the ANL fuse.

 

[centerline]

fuses are pretty simple to wire in, change out when needed and safe to use...

at first glance, one may think a circuit breaker, with all the modern technology wrapped up in it would be better.... sometimes its more convenient to push a button to reset it, but seldom is it a better system. even at their best, a circuit breaker system can never be expected to be as cheap and trouble free for as long as a fused system would be... sure, the fuse may blow, and the circuit breaker may trip, but every time a fuse blows you replace it with a new one, and every time a circuit breaker trips, it can be reset.... but circuit breakers can and do fail in three different ways.

sometimes you just get a bum part that doesnt work properly after installing it, and even the best ones can only be expected to be reset for some unknown number of times before they become weak (wear out) and need to be replaced.

sometimes you will have one just stop working entirely and wont pass power thru it.... and then there is the worst failure of all, which is where the circuit breaker passes enough power so that it can be tested with a meter or test light, but does not pass enough amps to power the component properly, yet does not trip.. this can lead to damage of the component, and cause dangerous heat levels within the circuit...
good circuit breakers are built with a heat sensitive solder link inside them (a "fuse") so if it gets too hot it can melt out and kill the downstream circuit.... sometimes this happens prematurely.

the problem is that very few circuit breaker manufactures build their breakers for a damp enviroment, and even though not all boat are very damp, some definitely are.
so with a GOOD breaker built for a marine enviroment, you can expect some dependability for quite sometime, but most people seem to look for the cheapest breakers they can get and this will more often than not be a substandard installation for their boat....

when you have electrical problems with circuit breakers installed, the problem can be not so obvious and hard to pin point, where as with a fuse, it is either good or it isnt.
I have seen a couple times where a fuse is visually fine and should be good, but it wont pass power thru it, but its a quick and easy process to insert another one in its place.

a fuse system is much cheaper, simpler and more dependable and easier to repair, but if all the circuits are fine and perfect, installed with quality parts and things are carefully kept in order, there should be no issues with either system for a long time.

I prefer a nice compact, easy to see/inspect fuse panel installation over circuit breakers, for all the reasons listed above.

 

[cyclecalm]

I know this doesn't answer all of your questions but it might help a little with determining if you can use a circuit breaker instead of a fuse on both connections.
https://www.dosupply.com/tech/2017/...ference-between-a-fuse-and-a-circuit-breaker/
https://www.renogy.com/blog/how-to-fuse-your-solar-system/

 

[JohnShannon]

I would think a solar panel doesn't need a fuse, it is inherently current limited. So unless there is a short and a nuclear blast going off at the same time the panel won't put out more current than its Isc. The source of huge currents is the battery.

 

[uncledom]

Ken Cross

Fuses really are current limiting devices where as circuit breakers are heat over time. If there is a fault and you are trying to protect the circuit and especially the particular limitation of the wire size chosen for the job nothing beats a fuse.

 

[Maine Sail]

For anything directly connected to the battery bank the AIC of the fuse used matters. For most applications only a Class T, MRBF or ANL fuse meets the AIC requirement. The reason we don't use breakers at the battery bank is because they can physically weld shut if the AIC rating (Amperage Interrupt Capacity) is too low for the bank. MRBF fuses (Marine Rated Battery Fuses) mounted to a busbar is a common way to wire a charge bus. Be aware that in most cases the fuses for any PV or wind system need to be within 7" of the source of power (the battery bank). Fuses before the controller, on the PV side, in most marine applications, are not necessary if the wind or PV array is "current limited". Current limited just means that under no circumstance can the source develop more current than can fry the wire. If the wire was sized for minimal voltage drop, eg; 3% or less, then the PV or wind can't toast the wire. The battery bank can however, so this is why the over current protection goes at the battery end.