Power feed to Equipment

[samrat8888]

I have a question regarding power feed to an equipment.

The equipment is a 450hp compressor and it demands 480 VAC. The distance between the compressor and Substation from where we have planned to feed it is 600ft.
We have done the cable sizing and found that 2 parallel runs of 3C X1 500 kcmil is good for the feed.

But at present there is a feed available from the Substation to a panel having distribution block in it, half way around 400ft having cable of 3 runs of 3C X1 of 500kcmil.

So my questions are:-

1) Can we reduce the cable size for remaining 200ft, considering there is less voltage drop for the first 400 ft as it has 3 runs and then make 2 runs of 350 kcmil?
2) Is it allowed to change the size of cable feeding same equipment half way.

 

[Jraef]

Duplicate thread

 

[jumper]

Duplicate thread

Re-opened, other one was already closed.

 

[jumper]

I did not check wire sizes, but:

1) Yes.

2) Yes

FYI, it does not matter where you splice in a bigger wire for VD. First, middle, or last.

No part or the run may contain a conductor smaller than the ampacity needed sized for the OCPD.

 

[samrat8888]

Hey - Can you please check NEC 310.10 H (2). there it says that for parallel connection all the cables shall be of same size in circular mil area.

I did not check wire sizes, but:

1) Yes.

2) Yes

FYI, it does not matter where you splice in a bigger wire for VD. First, middle, or last.

No part or the run may contain a conductor smaller than the ampacity needed sized for the OCPD.

 

[GoldDigger]

And I think that means that within each segment all the wires must be the same size (and length), not that the size must remain unchanged from end to end.
Worst case an inspector may want to see all of the wires solidly bonded together at the point where they change size. Than you would have separate parallel runs for each segment.

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