T class fuse and breaker placement

[Wineguy]

Setting up an offgrid 3 kW AIO connected to a single 48V LFP 100 ah battery (with a solar array as well!). My question is regarding placement and order of placement of 125 A t class fuse, 125 amp Nader breaker and bus bar between the battery and the AIO. I need to convert the 48 V to 12 V to run a few things in the cabin so I need to convert the 48 V to 12 V as well. My understanding is that the T class fuse should be closest to the battery so was planning on installing the t class fuse in a fuse holder near the positive terminal then connecting the fuse to a 275A bus bar then connecting the 125A nader breaker then connecting to the AIO. (see attached figure) Is this the right order? does it make a difference where the Nader breaker is located? Do I need the T class fuse along with the Nader Breaker? Also, I was thinking of putting in a DC breaker downstream of the 48V to 12 V converter and inline fuse. Is this needed? Any help here is appreciated.

 

[time2roll]

The breaker is redundant at the same rating as the Class-T. I would skip it.
Only when the wire size is stepped down there needs to be an appropriate smaller rated fuse. This would include the wire to the 48-12 converter. After the converter probably does not need a fuse if the wire is rated for the full 12v amps available. The converter will limit the output amps.

 

[Sennen]

Fuse should be as close to the positive bus (or battery if no bus) as possible

 

[OM617YOTA]

I have class T fuses between my batteries and bus bars, and added breakers between the inverters and bus bars for use as switches. When I designed and built the system I was thinking I'd be disconnecting the inverters occasionally.

In practice, the breakers haven't been needed at all.