Beginner Question

[Chromdome35]

I have a fuse block, that has 6 fuses

https://www.amazon.com/gp/product/B07X32KGF8/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

My question is this...can I connect 3 different 12v inputs to the block and use the Main Pos/Neg terminals to run to my load? I'm using it in reverse to the normal use where the input would connect to the two main terminals and the loads to the 6 connection points.

Only 1 of the 6 inputs would be active at any given time.

 

[ghostwriter66]

Short answer YES

Long answer ... YYYEEEEESSSSSSS

 

[Chromdome35]

Short answer YES

Long answer ... YYYEEEEESSSSSSS

Thank you for the quick response!

 

[HRTKD]

Yes, you could do that. However, overcurrent protection (the fuse) is used to protect the wire. If you have the fuse at the end of the wire, it isn't in a position to do its job.

 

[Chromdome35]

HRTKD, could you expand on your post?

I'm going to have the following setup

Variable input voltage between 12v and 40v -> Fuse Block (the one mentioned) -> Buck Converter 5-40v to 12v > Fuse (inline) > 12v Load

If the incoming feed is out of bounds, will the first fuse block not catch it at that point? After the Buck Converter, the inline fuse should protect the load in case the buck converter goes bad?

Thank you for helping me understand, I'm really new to all this 12v wiring.

 

[HRTKD]

Based on your description of how you plan to use that fuse block, the fuses will be at the end of the wire, not the beginning of the wire. This is how it your circuits should look:

source -> fuse -> wire -> bus bar
source -> fuse -> wire -> bus bar -> fuse -> buck converter -> (could put a fuse here too) -> 12v load
source -> fuse -> wire -> bus bar

 

[Chromdome35]

Based on your description of how you plan to use that fuse block, the fuses will be at the end of the wire, not the beginning of the wire. This is how it your circuits should look:

source -> fuse -> wire -> bus bar
source -> fuse -> wire -> bus bar -> fuse -> buck converter -> (could put a fuse here too) -> 12v load
source -> fuse -> wire -> bus bar

Thank you for explaining, I understand what you are saying.

In the ( source -> fuse -> wire ) relationship, how close to the source input does the fuse need to be. The distance from the input to the fuse block is about 3" of 14ga wire. An inline fuse seems redundant with the fused bus bar no more than 1/2"-1" of wire away from the output side of the inline fuse. The inline fuse will occupy almost the entire physical gap between the input and the fuse block. I am not asking to be argumentative, I'm just trying to learn.

 

[time2roll]

3" I think you are fine. If the load causes the overcurrent the fuse will open. I assume the source can exceed 30-35 amps.

 

[HRTKD]

I've seen fuses used between devices instead of wire. On one extreme, we could say that every connection needs to be fused. But, we can also be reasonable and say that with a sufficiently large wire, that is rated for far more amps than could ever go through it, a fuse may not be necessary.

 

[Chromdome35]

3" I think you are fine. If the load causes the overcurrent the fuse will open. I assume the source can exceed 30-35 amps.

I'm planning on the load pulling a max of 8-12 amps, source be a 12v Battery, or a cigarette lighter power adapter. The wiring will be 14ga with the longest run being no more than 2 ft.

 

[Deleted member 23531]

Hey @HRTKD , I don't think the fuse and wire know who comes "first" in the circuit, and anyway the ordering is based on a positive current convention which is just a convention. By the time a fuse opens, the same number of electrons will have passed through the wire and the fuse regardless of whether you order them (wire_a -> fuse -> wire_b) or (wire_b -> fuse -> wire_a) or (wire_a -> wire_b -> fuse), etc. since all the wires we deal with here are shorter than the length that would require thinking about transmission line / time-of-flight effects.