400 sub panel 200% Nuetral

[kyleapec]

I have a Sub Panel fed from an Isolated XFMR, would (3) 500 MCM(s) and a 500 MCM neutral be considered a 200% Neutral?

 

[infinity]

No you would need parallel 500 kcmil neutrals or 200% of the phase conductors. Also 500 kcmil cannot be used with a 400 amp OCPD on the secondary because the ampacity is only 380 amps.

Welcome to the Forum.

 

[kwired]

I have a Sub Panel fed from an Isolated XFMR, would (3) 500 MCM(s) and a 500 MCM neutral be considered a 200% Neutral?

That would only be 100% neutral in relation to the ungrounded conductors.

 

[dkidd]

Also 500 kcmil cannot be used with a 400 amp OCPD on the secondary because the ampacity is only 380 amps.

Welcome to the Forum.

What about 240.4(B)?

 

[infinity]

What about 240.4(B)?

Does not apply due to 240.21(C).

240.21(C) Transformer Secondary Conductors. A set of con-
ductors feeding a single load, or each set of conductors feed-
ing separate loads, shall be permitted to be connected to a
transformer secondary, without overcurrent protection at the
secondary, as specified in 240.21(C)(1) through (C)(6). The
provisions of 240.4(B) shall not be permitted for transformer
secondary conductors.
Informational Note: For overcurrent protection require-
ments for transformers, see 450.3.

 

[Dennis Alwon]

What is the neutral load? If the neutral load is not high than 500 kcm may be 200% but if they want 200% of the conductors then you would need to parallel as Trevor stated