Bending space

[mdbennett]

I'm designing a 400 HP, 480V, NEMA 12 soft starter cabinet to meet UL508A. What is the distance from the inside top of the cabinet to the top of the MCCB? My research seems to indicate 24 inches.

 

[augie47]

Can't speak for UK508 but for a reference you can check NEC 312.6. In NEC it dpeends on the wire size and number of conductors but it appears the highest distance would be 15" or 16"

 

[mdbennett]

Here are my numbers, 400 HP @ 460V = 477 A, 125% of 477 = 596A. Using 75 deg C conductors (NEC 310.16, UL table 28.1), size should be 1500 kcmil. Bending space (NEC 312.6b, UL table 25.1) for that size conductor (1 per terminal) is 24 inches. Not sure I'm reading specs correctly.

 

[retirede]

Keep in mind that it’s unlikely it gets installed using 1500MCM. Parallel smaller conductors are likely to be used.

 

[mdbennett]

Good point. It looks like if I recommend two 350 kcmil per terminal, bending space is 12 inches, three 3/0 per terminal, bending space is 8 inches.