Breaker Switches vs Fuses

[roverhi]

The big difference for the user is you know when a cirucit is interupted by a beaker. The breaker trips and you can see that it's tripped. With a fuse, the circuit won't energize but you don't know whether it's because of a fuse, bad connection down the line, or just that everything on the circuit suddenly went on holiday. You have to get your trusty multi meter and test the circuit at the fuse and/or pull the fuse and visually confirm that it's blown.

To me the ability to see that a C/B has tripped has worth the additional cost over fuses.

[noelex 77]

Originally Posted by ranger42c

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.

True, but a CB generally does both jobs on a boat. Both circuit/equipment protection and user-controlled ON/OFF. It needs to perform both tasks satisfactorily.

[mitiempo]

Originally Posted by Cadence

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.

For windlasses and starting circuits fusing is my first choice. In declining order of interrupt capacity are T class, MRBF terminal fuses, and ANL fuses. It is expensive to find breakers that have the interrupt capacity of MRBF or T class fuses, if you can find them.

[noelex 77]

Originally Posted by mitiempo

For windlasses and starting circuits fusing is my first choice. In declining order of interrupt capacity are T class, MRBF terminal fuses, and ANL fuses. It is expensive to find breakers that have the interrupt capacity of MRBF or T class fuses, if you can find them.

I think Mitiempo has a good point. The IC rating is an important factor. Unfortunatly it is a complicated subject. To correctly calculate the minimum IC rating depends on factors such as the battery capacity and wire size.

I slightly disagree with the suggestion that: "It is expensive to find breakers that have the interrupt capacity of MRBF or T class fuses". I think it is more accurate to suggest "It is difficult (or impossible) to find marine breakers that have the interrupt capacity of MRBF or T class fuses". If you switch to industrial CB often even the smallest models have IC that are similar to T class fuses. These are not expensive. Larger models do even better if you need extra headroom.

This is just one of reasons are why commercial boats use this type CB rather than "marine CB" for general circuit protection. I think many pleasure boats could follow their example, although for most circuits marine CB have more than adequate IC. (Inverters are often an exception).

There are more significant advantages of industrial CB such as easy replacement and longer life.

[john61ct]

Originally Posted by Cadence

Time delay breakers are for high starting currents, generally motors.

My point was you are likely to get a delayed CB when that isn't the best choice, and researching those specs is something many (most) owners would rather not get into.

Hence my advice to stick to fuses when protecting heavy-current wires.

[john61ct]

Originally Posted by noelex 77

If you switch to industrial CB often even the smallest models have IC that are similar to T class fuses. These are not expensive. Larger models do even better if you need extra headroom.

This is just one of reasons are why commercial boats use this type CB rather than "marine CB" for general circuit protection. I think many pleasure boats could follow their example

Links would be most appreciated.

[ranger58sb]

Originally Posted by noelex 77

True, but a CB generally does both jobs on a boat. Both circuit/equipment protection and user-controlled ON/OFF. It needs to perform both tasks satisfactorily.

Yep, good expansion. Just meant to be sure OP recognized all switches are not "circuit breakers" in the protection sense.... and that circuit breakers are usually installed when the main goal is probably about protecting circuits and equipments, i.e., more than just a simple ON/OFF.

-Chris

[Cadence]

Originally Posted by john61ct

My point was you are likely to get a delayed CB when that isn't the best choice, and researching those specs is something many (most) owners would rather not get into.

Hence my advice to stick to fuses when protecting heavy-current wires.

A bus fuse close to the equipment is a good idea in case of a catastrophic failure.

[john61ct]

Also be aware CB switches do have a limited cycle life.

[Ironman162]

My boat has double pole switches with fuses in both the positive and negative on the distribution panel.
It uses glass automotive fuses that are readily available and quick and easy to replace using Bakelite screw cap fuse holders.
This may sound old-fashioned but I prefer fuses in both legs, they are quicker than circuit breakers and more robust.
The only thing is the older I get I can't always see the fuse element so clearly and need a small continuity tester to tell if a fuse is actually blown..

[TooCoys]

I found the AC fuse panel today. It has shotgun shell looking fuses with glass tops on them!!!

[transmitterdan]

Originally Posted by TooCoys

I found the AC fuse panel today. It has shotgun shell looking fuses with glass tops on them!!!

These are probably original equipment fuses from the 60's. They were common in homes and boats of the day. Today no one uses fuses in AC panels in homes or boats.

You will find a ton of things in a 50 year old boat that need replacing. You are just beginning to peel the onion I'm afraid.

[mitiempo]

Originally Posted by Cadence

A bus fuse close to the equipment is a good idea in case of a catastrophic failure.

Proper location is close to the source - the battery. The load, whatever it is, is limited in output to its design, as an alternater, charger, solar, etc. Other loads have no output potential. A battery or bank can output thousands of amps if short circuited.

[mitiempo]

Originally Posted by TooCoys

I found the AC fuse panel today. It has shotgun shell looking fuses with glass tops on them!!!

AC should have breakers, not fuses. Double pole for the main, single for circuits.

[Squanderbucks]

Circuit breakers are the easiest to maintain and are preferred to glass fuses in general. Also, fuses are prone to needing to be removed and cleaned from time to time as they build up a film oxidation on the metal end caps that make loss of power intermittent and hard to track down sometimes.
However most electronics on boats draw so few AMPs that they require very small fuses 0.5 to 7.5 for example. Circuit breakers are not readily available for sizes less than 5 AMPS that I am aware of. Also fuses are faster acting in many cases.
Squander Bucks was built with all glass fuses and I switched it all over to Circuit breakers except for the Navigation and Entertainment stuff which has a fuse panel of it's own that I changed over to the ATO automotive fuses which I like better. Blue Seas makes all these that you need.
The ATO fuses don't seem to be as prone to the intermittent gumming up as the glass ones, are easier to insert and remove and can tell visually if they are blown easier. Personal choice.