diy solar

diy solar

need advise for 24v 300A breakers

FilterGuy said:
That style breaker really should not be built for more than 150-200 amps.
Click to expand...

Let me add to what @FilterGuy guy is saying.
That breaker and all the cheap one's like it are just a steaming pile of crap.
If you are lucky they trip to soon.
If you are unlucky they weld shut and therefore fail to protect you and your family from an electrical fire.
The only 2 manufacturers I trust are littelfuse and bussman.
Bluesea rebrands bussman so those are good as well.
 
If you check the bussman/blueseas line of that style breaker, you will notice that they top out at 200 amps. There is a reason for this. You just can't cram enough copper and controls into a breaker that size that can handle more current.
 
BTW: Eaton is another reputable breaker company and their breakers of that style also top out at 200A.
 
FilterGuy said:
That style breaker really should not be built for more than 150-200 amps.
Click to expand...
For giggles I bought a few of those off ebay and tested them. If they could be called anything, apart from junk, they'd be 80A but there was so much variance between each one that even that would be pressing it. There are plenty of other reasons why they shouldn't be used too, no arc trap, housing is flammable, and it's not sealed either. At least the one in the opening post doesn't have Ignition Protected written on it, which is the final insult you see when looking at it as your premises burns down.
 
After reading this, I think it would be cool if I were to order a handfull of these and record a video comparing them, even compared to the name-brand Bussman type. In my experience however, these breakers really don't hold well, and if you try feeding power backward (From load to line, for example if you used an inverter/charger) then the trip rating is FAR lower. I also doubt their claim that they are "Ignition Protected". It would be fun to intentionally trip a couple of them while in an environment that is rich in flammable vapor. A welding machine might make this test easier.
 
Adding to what others have said, circuit protection is a great place to avoid buying the cheap no-name amazon/ebay/aliexpress components, and buying from reputable companies with a track record.

smoothJoey said:
The only 2 manufacturers I trust are littelfuse and bussman.
Bluesea rebrands bussman so those are good as well.
Click to expand...
FilterGuy said:
BTW: Eaton is another reputable breaker company and their breakers of that style also top out at 200A.
Click to expand...

Best I can tell Eaton = Cooper = Bussmann = Buss. Or at least all these brands are affiliated in some capacity. I have the vague impression Cooper and Bussmann are sub brands of Eaton. Then, there is Blue Sea which rebrands them under their own brand name.
 
Last edited:
Dzl said:
Adding to what others have said, circuit protection is a great place to avoid buying the cheap no-name amazon/ebay/aliexpress components, and buying from reputable companies with a track record.




Best I can tell Eaton = Cooper = Bussmann = Buss. Or at least all these brands are affiliated in some capacity. I have the vague impression Cooper and Bussmann are sub brands of Eaton. Then their is Blue Sea which rebrands them under their own brand name.
Click to expand...

I did not know that..... I learn something new every day..... now I that I have learned something I can go back to bed! ?
 
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I just realized that we never answered the OPs request for a recommended alternative. Unfortunately, I am not aware of a good 300A breaker. Midnight solar makes some big 'main' DC breakers but 1) they top out at 250A 2) they are expensive and 3) they require a box to mount them in.

I used to have an attitude that breakers are the only way to go. I wanted to be able to reset the breaker, no matter what. However after I tried researching high current breakers, and then thought about it a while, I no longer think that way. The only reason to mandate a breaker instead of a fuse is if you think there is a reasonably good chance the overload protection will trip during normal use. If a design is going to blow a 300A circuit in normal operation....that design needs to be changed. The only time a 300A circuit should blow is in an extreme catastrophic condition. At that point, changing a fuse is the least of your worries.

BTW: all of my BMS's have over-current protect so they will almost always shut off before a breaker would anyway.

So.... for a 300A circuit, I would put in a fuse and have a spare on hand. (Yes, I fuse my battery even if the BMS also has over-current protect). Even at 200A DC I use a fuse instead of a breaker (breakers are much more likely to fail than a fuse. ) I generally don't consider using a breaker for anything over ~150A.

If there were quality high current breakers available at a reasonable price, I might use them. However, I can not find such a beast. If you find one, let us know.
 
I doubt there are any for what DIYers would consider a reasonable price. High current breakers sure do exist but the real ones are proper industrial grade equipment that you find protecting generators etc.
 
FilterGuy said:
I just realized that we never answered the OPs request for a recommended alternative. Unfortunately, I am not aware of a good 300A breaker. Midnight solar makes some big 'main' DC breakers but 1) they top out at 250A 2) they are expensive and 3) they require a box to mount them in.

I used to have an attitude that breakers are the only way to go. I wanted to be able to reset the breaker, no matter what. However after I tried researching high current breakers, and then thought about it a while, I no longer think that way. The only reason to mandate a breaker instead of a fuse is if you think there is a reasonably good chance the overload protection will trip during normal use. If a design is going to blow a 300A circuit in normal operation....that design needs to be changed. The only time a 300A circuit should blow is in an extreme catastrophic condition. At that point, changing a fuse is the least of your worries.

BTW: all of my BMS's have over-current protect so they will almost always shut off before a breaker would anyway.

So.... for a 300A circuit, I would put in a fuse and have a spare on hand. (Yes, I fuse my battery even if the BMS also has over-current protect). Even at 200A DC I use a fuse instead of a breaker (breakers are much more likely to fail than a fuse. ) I generally don't consider using a breaker for anything over ~150A.

If there were quality high current breakers available at a reasonable price, I might use them. However, I can not find such a beast. If you find one, let us know.
Click to expand...

I second this motion. Use a fuse. You should never have a fault on a line that large that should just be reset. If you blow a 300A fuse or circuit breaker that was sized properly, you should investigate the fault and not just reset the breaker. Use a fuse with a separate disconnect switch if you need a disconnect.

We may be able to help more if you share your circuit with us so that we can see how you are using the breaker.
 
gpower07 said:
my system only max out at 120A. I just double the amp. 200A is enough.
Click to expand...
You can do that, but make sure your wiring is all sized for 200A. (You don't want your wires to burn before fuse blows).

If your max truly is 120A, I would use a 150A fuse.
 
This one is closer to bluesea but only goes to 90 celcius.
www.cerrowire.com

Cerrowire Resources - Ampacity Charts

Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.
www.cerrowire.com www.cerrowire.com
 
The interesting thing is that if you look at the chart just below that, they show 4AWG topping out at 100A...
 
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