Another warning about DC MCBs

[Crossy]

The use of AC rated MCBs on DC circuits has been discussed a few times, but what about mis-wiring of DC MCBs?

 

Check those polarity and direction markings. It matters!

 

 

[sezze]

I fail to see why this happens . Is part of my job to always understand why something happens and find a explanation and try to fix it ( the fixing in this case is easy ) . The current flows from - to + so it must be that the - wiring inside must be larger/bigger gaps , so that the current really stops directly when it trips ? When changing direction or polarity , then the flow keeps going for a while making a new connection by melting pieces , causing flames ?

Is there any other reason ? If not , are there no brands around which do got same wiring inside , or is it something normal ? Im just wondering ...

[SomchaiDIY]

43 minutes ago, sezze said:

I fail to see why this happens . Is part of my job to always understand why something happens and find a explanation and try to fix it ( the fixing in this case is easy ) . The current flows from - to + so it must be that the - wiring inside must be larger/bigger gaps , so that the current really stops directly when it trips ? When changing direction or polarity , then the flow keeps going for a while making a new connection by melting pieces , causing flames ?

Is there any other reason ? If not , are there no brands around which do got same wiring inside , or is it something normal ? Im just wondering ...

electric arc can move with field of magnet

 

polarized breaker has magnet to direct arc into safe chamber

 

if polarity not correct magnet will push arc to the incorrect direction and are will continue burn

[OneMoreFarang]

1 hour ago, sezze said:

I fail to see why this happens

I hope you don't expect any detailed and correct answer in this forum.

Obviously, if you are lucky, you may get a correct answer. But IMHO it is a lot more likely to read incorrect or maybe partly correct comments.

 

If you really want an answer, maybe go here, they have great experts:

Electrical Engineering Stack Exchange

 

[SomchaiDIY]

28 minutes ago, OneMoreFarang said:

I hope you don't expect any detailed and correct answer in this forum.

Obviously, if you are lucky, you may get a correct answer. But IMHO it is a lot more likely to read incorrect or maybe partly correct comments.

 

If you really want an answer, maybe go here, they have great experts:

Electrical Engineering Stack Exchange

 

sometime is best to keep simple explain not all people need detail paper

 

for detail this paper help understand why some of the polarize breaker fail if connected incorrect 

 

energies-15-02776-v2.pdf

[TronxII]

On 10/21/2022 at 6:49 PM, OneMoreFarang said:

I hope you don't expect any detailed and correct answer in this forum.

...

 

 

On 10/21/2022 at 7:19 PM, SomchaiDIY said:

sometime is best to keep simple explain not all people need detail paper

 

 

Apparently @SomchaiDIY  answered this question very well. If all the falangs posting here had the same knowledge as he ...

 

Thanks SomchaiDIY

 

And another thought:  so these MCBs are a no go in a Panel combiner box where you parallel panels.

 

 

 

 

 

[Crossy]

2 hours ago, TronxII said:

And another thought:  so these MCBs are a no go in a Panel combiner box where you parallel panels.

 

So long as they are DC rated for the total string voltage and correctly wired they are 100% fine in your combiner box. Many include individual fuses for each parallel string and use an MCB as an overall isolator.

[degrub]

Good paper.

[OneMoreFarang]

7 hours ago, TronxII said:

Apparently @SomchaiDIY  answered this question very well. If all the falangs posting here had the same knowledge as he ...

I don't know how good his answer is, maybe it's perfect.

 

The problem with forums like this is that the knowledge level of the participants is somewhere between 0 to 100%. If someone with, let's say, 2% knowledge asks a question and maybe several people with 10% or 20% knowledge answer, then often the answers are completely different. But because the two people who answer have considerably more knowledge than the person who asks both answers might sound like expert answers. After all, those guys know 10 times more.

And then maybe a top expert sees those answers and he could explain that solution B is only relevant in this conditions and solution C is only relevant in that condition. But ..... and then it gets complicated and all the people with no or little knowledge don't understand it anymore.

 

For me that is a reason to look for answers to "complicated" questions on expert websites. And I don't really have to understand everything. If the experts agree that B or C is a good solution then let's do that.

There is a reason why some people study these things for years...

[SomchaiDIY]

On 10/21/2022 at 11:49 PM, OneMoreFarang said:

I hope you don't expect any detailed and correct answer in this forum.

interesting why you waste time asking many question at this forums

 

 

2 hours ago, OneMoreFarang said:

I don't know how good his answer is, maybe it's perfect.

i made support to my post with university paper on this subject

 

if no time to read paper best not comment

 

**************************************************************************************************

 

10 hours ago, TronxII said:

Apparently @SomchaiDIY  answered this question very well. If all the falangs posting here had the same knowledge as he

thank you for this reply i try to fact check my tech knowledge before post

 

most forums have mix of good knowledge people and those who try help and people who make garbage

 

best idea to pick through posts and make own internet research if important

 

this subject of dc breaker is important for good safety and good if diy solar people understand danger

 

i sure if people post bad info in this safety topic tech people will make correction

 

[OneMoreFarang]

4 hours ago, SomchaiDIY said:

thank you for this reply i try to fact check my tech knowledge before post

 

most forums have mix of good knowledge people and those who try help and people who make garbage

It's great that you fact check what you post. But I am sure you will agree many people don't do that.

And this was/is my point.

If it is important then look for experts, and only experts. 

[Crossy]

And with that I'm going to close this thread.