Using Different wiring sizes?

[ManKzin]

I was wondering if I can use different wire sizes in the same line. For example. For my MPPT and 12 Volt load line to the Fuse box (sized to 4 AWG), can I put in 1/0 AWG from the battery bus bar (110 Class T Fuse) to the Disconnect Switch, then to an interior positive bus bar and then have the 4 AWG travel from there to the fuse box or MPPT?

 

[BatteryBuff]

I was wondering if I can use different wire sizes in the same line. For example. For my MPPT and 12 Volt load line to the Fuse box (sized to 4 AWG), can I put in 1/0 AWG from the battery bus bar (110 Class T Fuse) to the Disconnect Switch, then to an interior positive bus bar and then have the 4 AWG travel from there to the fuse box or MPPT?

You can use multiple wire sizes but each section of wire must meet the minimum gauge requirement for the current that is has to carry.

 

[time2roll]

Every place that a wire steps down in size needs the appropriate smaller fuse protection.

 

[Rednecktek]

Every place that a wire steps down in size needs the appropriate smaller fuse protection.

Or just do like I did in my camper (where I had wire I couldn't access to replace) and just size your fusing for the smallest guage in the run.

I.E. If you pull a 12awg wire from the fuse block, then splice it to a 14awg wire, then to your load, just treat the entire run as a 14awg run.

 

[ManKzin]

Every place that a wire steps down in size needs the appropriate smaller fuse protection.

So I would have to have another 100A Class T Fuse when I step down from the 1/0 AWG (using a bus bar) to the 4 AWG wire. So it's best to just use the 4 AWG throughout. Got it. Was just trying to see if I could use the 1/0 AWG wire I have that I mistakenlu brought and had cut up

 

[Suijkerbuijk]

So I would have to have another 100A Class T Fuse when I step down from the 1/0 AWG (using a bus bar) to the 4 AWG wire. So it's best to just use the 4 AWG throughout. Got it. Was just trying to see if I could use the 1/0 AWG wire I have that I mistakenlu brought and had cut up

No only the main cable from the battery have to be a t-fuse
After that you can use c20/anl fuse .
Not the mega fuse that is shit .

 

[ManKzin]

Or just do like I did in my camper (where I had wire I couldn't access to replace) and just size your fusing for the smallest guage in the run.

I.E. If you pull a 12awg wire from the fuse block, then splice it to a 14awg wire, then to your load, just treat the entire run as a 14awg run.

That was what I was thinking, but another poster said I had to have another fuse at the step down. Hmm need some more response before I decide. Personally I just see it as oversizing a recommended 4 AWG to a 1/0 and then stepping it down at the bus bar where the 2 devices (MPPT & 12V fuse box) each have their own line. Thought it would be safer and less heat if both were running at 100%. And yes I know the MPPT gets its main power from the solar side

 

[ManKzin]

No only the main cable from the battery have to be a t-fuse
After that you can use c20/anl fuse .
Not the mega fuse that is shit .

ok. I understand. I actually have a few ANL fuses holders I could use before the 80A MPPT and the 100A fuse box, if I decide to go that route. Or I will just use the 4 AWG after the battery bus bar and not add any fuses after that. Just trying to find a use for some 1/0 AWG wire I mistakenly brought and cut up.

 

[time2roll]

So I would have to have another 100A Class T Fuse when I step down from the 1/0 AWG (using a bus bar) to the 4 AWG wire. So it's best to just use the 4 AWG throughout. Got it. Was just trying to see if I could use the 1/0 AWG wire I have that I mistakenlu brought and had cut up

OK so if you have a bunch of mismatched wire fused at the level for the smallest wire then no additional fuse is needed.
Best to use the same and proper size wire with correct fusing.

 

[Suijkerbuijk]

That was what I was thinking, but another poster said I had to have another fuse at the step down. Hmm need some more response before I decide. Personally I just see it as oversizing a recommended 4 AWG to a 1/0 and then stepping it down at the bus bar where the 2 devices (MPPT & 12V fuse box) each have their own line. Thought it would be safer and less heat if both were running at 100%. And yes I know the MPPT gets its main power from the solar side

You have to see it like this .
If the fuse is higher than the cable .
Than the cable become a fuse for the fuse .

A fuse is to protect the cable .
So if you stap down a cable on the main cable with no fuse .
That stap down cable will burn.
If you set a really low fuse and a higher cable .
But you pull low amps .
Than you can do it .
So long the cable max is higher than the fuse.
So if you split the cable to a lower cable but that cable is still higher than the fuse ampère .
Than its fine.

Personal i fuse the cable .
I will not safe some small cash on a fuse .
Well my house burn down.

 

[ManKzin]

You have to see it like this .
If the fuse is higher than the cable .
Than the cable become a fuse for the fuse .

A fuse is to protect the cable .
So if you stap down a cable on the main cable with no fuse .
That stap down cable will burn.
If you set a really low fuse and a higher cable .
But you pull low amps .
Than you can do it .
So long the cable max is higher than the fuse.
So if you split the cable to a lower cable but that cable is still higher than the fuse ampère .
Than its fine.

Personal i fuse the cable .
I will not safe some small cash on a fuse .
Well my house burn down.

I thought since I was putting a Class T 110A fuse which comes off the bus bar then to the 1/0 AWG which then passes through the disconnected switch to another bus bar which has the 80A MPPT, 12V 100A Fuse box and positive shunt wire. That it be protected by the 100A Class T fuse. I would understand if the Class T fuse was say 350A in this line, then I would have to put a 100A fuse on the MPPT and one on the fuse box.
Glad I asked this question.