Xfmr secondary fuse and breaker

[msteiner]

For xfmrs less than 600V, NEC Table 450.3(B) allows up to 6 fuses or up to 6 circuit breakers on the secondary, grouped in one location. But does it permit a mix of fuses and breakers? I'm designing a new installation with a 500kVA, 480-208/120V dry-type xfmr, and my preliminary design shows an 800A fused disconnect and an 800A MCB panelboard, all grouped together. Is this permitted?

 

[augie47]

For xfmrs less than 600V, NEC Table 450.3(B) allows up to 6 fuses or up to 6 circuit breakers on the secondary, grouped in one location.

not sure I see any limitations in 450.3 .
Art 230 or Art 225 might limit you to (6) disconnects if these are serving as "service".
I know of nothing prohibiting a mix of type.

 

[Pierre C Belarge]

I am with Augie here, I do not see where the NEC would prohibit such an installation as described.

 

[don_resqcapt19]

I don't see any issue with a mix of the two as the secondary protection for the transformer, just make sure you don't forget about the rules in 240.21(C) for the required protection of the secondary conductors.

 

[Pierre C Belarge]

I don't see any issue with a mix of the two as the secondary protection for the transformer, just make sure you don't forget about the rules in 240.21(C) for the required protection of the secondary conductors.

How about adding to this, 408.36(B)

 

[don_resqcapt19]

How about adding to this, 408.36(B)

Pierre,
The original post says the panel has a main breaker so it would be in compliance with that section.

 

[Pierre C Belarge]

Pierre,
The original post says the panel has a main breaker so it would be in compliance with that section.

I see that.....now.