Service Disconnect vs Parallel Source Disconnect

[lordjim54]

On my new 400Amp panel, I see the following schematic:
See schematic on right side of link, https://assets.new.siemens.com/siem...81-9dce-1939c0e0480f/sie-cs-mc3042s1400sc.pdf

The main line coming in branches out to 3 locations: M1, M2 and M3. (M2 is the local bus for the main house).

I need another 200Amp breaker to go to a subpanel 80 ft. away to a garage/ADU (with solar panels on ADU roof).

I want to use M3 for the feed to the ADU and leave M1 unused. The schematic shows that M1 and M3 are equal so I should be able to use either one.

The reason I want to use M3 is that the 2.5" conduit is coming up thru the footing and is attached to the panel right below M3.

Is there any reason I shouldn't use M3 for the subpanel?

Thank you

 

[jaggedben]

In my opinion no reason you shouldn't. However an inspector who doesn't really understand these things or just wants to be a stickler might reject it based on the labeling that it's supposed to be for parallel energy. (The fact that your parallel energy source here (the solar) is connected to the same panel might help with that?)