Safety problem with feeders and branch circuits in the same wireway.

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That looks to be a three phase system, in an industrial setting, inside a cabinet. Other than that there are many unknowns. What equipment is this OCPD protecting
 
negative my friend, if the conductors at 75 degreee and the terminals are 75 degree, you can use 75 degree column
Equipment 100A or less is usually rated 60° on terminals. It's also on Mike Holt's books.

Maybe this molded breaker is 75° because it's industrial grade. And remember: that number in the table is BEFORE derating.
 
110.14(C) (1) the determination of termination provisions of equipment shall be based on 110.14(C)(1)((a) unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on Table 310.16 as appropriately modified by 310.12


Almost all panels, OCPD’s, and equipment I work with nowadays are listed for 75degree termination
 
110.14(C) (1) the determination of termination provisions of equipment shall be based on 110.14(C)(1)((a) unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on Table 310.16 as appropriately modified by 310.12


Almost all panels, OCPD’s, and equipment I work with nowadays are listed for 75degree termination
 
110.14(C) (1) the determination of termination provisions of equipment shall be based on 110.14(C)(1)((a) unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on Table 310.16 as appropriately modified by 310.12


Almost all panels, OCPD’s, and equipment I work with nowadays are listed for 75degree termination
It depends on what you use and the DERATING factors.

"(a) Equipment rated 100A or less must be sized using these rules:

 
Ok and your derating is based on the 90 degree column, what are you derate and adjustment factors??
I didn't do that building of the photo, I'm not aware of what calculations they did. I'm going to use a 60° breaker, so I must use the 60° column. So I must use a 1/0 AWG minimum BEFORE derating. The code doesn't allow less than that (for a 60° breaker in conduit). Not air. Not 75° terminals. It's not extreme. It's the minimum allowed by NEC.
 
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All square D breakers are now rated 75 degrees. If I was in an industrial setting wiring a three phase furnace that have sets of series elements at 80Amps per series I would consider 125 percent for my conductors. 100 A conductors at 60 degrees. I would also protect it with a 100 A OCPD

that would be a #1 copper, but because the ambient temperature will be high around this furnace, I would be using a 1/0 conductor protected by a 100 A OCPD per series. I can’t think of too many scenarios outside of industrial where you would use 1/0 on a 100A OCPD.

I just can’t see it in normal businesses
 
A. Conductors are to be sized using their ampacity from the insulation temperature rating column of Table 310.15(B)(16), which corresponds to the lowest temperature rating of any terminal, device, or conductor of the circuit [110.14(C)(1)]. Unless the equipment is listed and marked otherwise, conductor sizing for equipment terminations must be based on Table 310.15(B)(16) in accordance with (a) or (b) [110.14(C)(1)]:
 
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