I have been following our great forum for quite sometime now and realised a lot of people use fuses insteady of dc breakers. From my Electrical knowledge as a qualified electrician, the breaker has more advantages over the fuse. Is there any advantage that I might not be aware of which makes the fuse a darling to so many(besides quick reaction and lower price). I have been playing videos on youtube and realised in US they use dc breakers(midnight dc breakers etc) more than they do with fuses. I do realise even the hardwares here in SA dont have much of dc breakers.

@phoenix752, I agree with you and use DC MCB sub 100A.

46 minutes ago, phoenix752 said:

Is there any advantage that I might not be aware of which makes the fuse a darling to so many

SMA advocates that there should be a gap between MCB's for heating because they run full tilt. YMMV.

However, when it comes to the 300A inverter inputs I use fuses.

( Not that I have ever-priced a 300A DC MCB, I think they fall into the "if you have to ask the price..." category.

The only advantages that a circuit breaker presents (talking specifically about MCB`s) is that they are convenient in that you can visually see which breaker has tripped and then to reset the breaker you simply flick a switch.

 

But in DC applications where you have batteries with extremely high short circuit currents the breaking time of the correct fuse is unmatched by a circuit breaker. From a safety point of view fuses are the way to go if they are specified correctly and installed correctly.

Circuit breakers contacts can also weld together and then your cables becomes a slow blow fuse

1 hour ago, Jaws said:

The only advantages that a circuit breaker presents (talking specifically about MCB`s) is that they are convenient in that you can visually see which breaker has tripped and then to reset the breaker you simply flick a switch.

 

But in DC applications where you have batteries with extremely high short circuit currents the breaking time of the correct fuse is unmatched by a circuit breaker. From a safety point of view fuses are the way to go if they are specified correctly and installed correctly.

Circuit breakers contacts can also weld together and then your cables becomes a slow blow fuse

Oooh ok..so its all about the reaction time of fuses. Wonder why most appliances have built in fuses

7 minutes ago, phoenix752 said:

Oooh ok..so its all about the reaction time of fuses. Wonder why most appliances have built in fuses

I think is mainly about the cost.

 

If you look at Large Lead Acid battery installations with high  ISSC ratings even a "small" 40 A circuit breaker is "BIG" in physical size and then also relatively expensive.

Descrimination DC 24-48V.pdf

20 minutes ago, Jaws said:

I think is mainly about the cost.

 

If you look at Large Lead Acid battery installations with high  ISSC ratings even a "small" 40 A circuit breaker is "BIG" in physical size and then also relatively expensive.

Descrimination DC 24-48V.pdf 2.42 MB · 3 downloads

I get you Jaws. But in terms of cost I think fuses are costly in the long run in the sense that you have to change it after every faulty. But breakers is a matter of reseting and you are back online. I know of a guy who installed two axpects (48/5000VA) in parralel running from 4 Pylontech US2000 protected by a 80A fuse(he is amateur electrician of course). Each inverter had 9×JA solar 330s and the installation runs for about 5 days before the fuse blew up. So I think the fuses are not as efficient in real world as on paper. Because the 80A mark was surpassed so often it should have blown in matter of minutes

2 hours ago, Jaws said:

Circuit breakers contacts can also weld together and then your cables becomes a slow blow fuse

Fuses have a definitive degree of certainty about them, that an MCB doesn't.

I know I said I used MCB's for sub 100A,  I retract that, I had forgotten I have fuses on the battery strings.

I consider the batteries as the real source of oomph in the system.

 

2 hours ago, phoenix752 said:

costly in the long run

Only if you constantly blow them... I haven't blown a fuse in the last 6 years. So they definitely represent both a cost saving and a bit more safety.