800A Feeder

[mstrlucky74]

So I was told there are either 3 or 4 sets of 4’ w/4#600’s feedingthis MCC to be demolished(the solid line is the new feeder being spiced to theexisting incoming to feed a new board). The board feeding the existing MCC is480’ away. According to my reference calculations wouldn’t two sets be suffice?There is a tap as you can see that feeds an 800a panel which is also beingdemolished. Why I'm asking is because I have to splice(the solid line) to these existing incoming sets to feed the new board. Thanks.

 

[infinity]

Two sets of 600's would suffice for 800 amps but the additional sets are likely there for voltage drop compensation.

 

[mstrlucky74]

Two sets of 600's would suffice for 800 amps but the additional sets are likely there for voltage drop compensation.

Yea but even with VD that's a lot.

 

[Unbridled]

So I was told there are either 3 or 4 sets of 4’ w/4#600’s feedingthis MCC to be demolished(the solid line is the new feeder being spiced to theexisting incoming to feed a new board). The board feeding the existing MCC is480’ away. According to my reference calculations wouldn’t two sets be suffice?There is a tap as you can see that feeds an 800a panel which is also beingdemolished. Why I'm asking is because I have to splice(the solid line) to these existing incoming sets to feed the new board. Thanks.

If it were me, and I had 30 days, I would do a power ( KW) analysis on the existing MCC. then you could determine exactly what size feeder you need to run. Then C/O fuses in Service Disconnect accordingly.

 

[Smart $]

The existing 800A feeder supplies both an 800A MCB panelboard and a 1600A MCC. The drawing says up to 4 sets of 600's. Are you assuming 3 or 4 sets or do you have reliable information on existing?

Likely upsized for voltage drop (already mentioned) and future expansion (not previously mentioned). The splice, existing to new, has a note not in the picture. What does 'NOTE 1' say... verbatim?

 

[mstrlucky74]

The existing 800A feeder supplies both an 800A MCB panelboard and a 1600A MCC. The drawing says up to 4 sets of 600's. Are you assuming 3 or 4 sets or do you have reliable information on existing?

Likely upsized for voltage drop (already mentioned) and future expansion (not previously mentioned). The splice, existing to new, has a note not in the picture. What does 'NOTE 1' say... verbatim?

Note #1- Intercept existing feeder and extend to new DPpanel. Match existing feeder size. Field verify existing feeder configuration,provide lugs in new DP panel to match.

 

[infinity]

So I was told there are either 3 or 4 sets of 4’ w/4#600’s feedingthis MCC to be demolished(the solid line is the new feeder being spiced to theexisting incoming to feed a new board). The board feeding the existing MCC is480’ away. According to my reference calculations wouldn’t two sets be suffice?There is a tap as you can see that feeds an 800a panel which is also beingdemolished. Why I'm asking is because I have to splice(the solid line) to these existing incoming sets to feed the new board. Thanks.

I don't see a tap. The switchboard is 800 amps fed by an 800 amp OCPD but that point is moot. I see nothing wrong with the design even with extending with 4 sets of 600's.

 

[Smart $]

Note #1- Intercept existing feeder and extend to new DPpanel. Match existing feeder size. Field verify existing feeder configuration,provide lugs in new DP panel to match.

As previously mentioned, 2 sets of 600's are sufficient for 800A but at 480' at least three sets were used... and considering the existing MCC is rated 1600A, running 4 sets of 600's was probably done in consideration of both voltage drop and possible future needs. The Note specifically requires intercepting the existing configuration and extending to the new MCC. It seems to me that whoever is doing the specifying wants to maintain the ability to 'up rate' the feed without repulling wire. You can RFI the matter but I'd just do what is specified, charge accordingly, and move on.