1000 amp service feeder

[dvcraven0522]

I have a E.C. who likes to use the 80% rating of a CB to figure voltage drop calculation.

In a most recent scenario I am feeding a 1000 amp CT Enclosure ahead of a 1000 amp MDP. I am thinking I may need to use the full 1000 ampere as my starting point when performing my VD calculations using NEC 240.4 (C) even though I am on the line side of the OCPD.

Dan

 

[petersonra]

I have a E.C. who likes to use the 80% rating of a CB to figure voltage drop calculation.

In a most recent scenario I am feeding a 1000 amp CT Enclosure ahead of a 1000 amp MDP. I am thinking I may need to use the full 1000 ampere as my starting point when performing my VD calculations using NEC 240.4 (C) even though I am on the line side of the OCPD.

Dan

Where does it say any of this in the code?

I would figure out what the real load is and use that for the VD calculation. Worst case use the calculated load.

I don't see how 240.4(C) has anything to do with VD calculations.

 

[drktmplr12]

you certainly can use 80% for calculating VD, but you are probably penalizing yourself. to be clear, voltage drop limitations are not a requirement of the NEC. It's state building code energy conservation chapters. Make reasonable assumptions and be prepared to defend them if challenged by the AHJ. I personally use calculated demand load. Easier to do with industrial facilities because they are simple to model under peak capacity conditions.

 

[electrofelon]

I have a E.C. who likes to use the 80% rating of a CB to figure voltage drop calculation.

In a most recent scenario I am feeding a 1000 amp CT Enclosure ahead of a 1000 amp MDP. I am thinking I may need to use the full 1000 ampere as my starting point when performing my VD calculations using NEC 240.4 (C) even though I am on the line side of the OCPD.

Dan

I would recommend not using the term "service feeder". These are both specifically defined things that are mutually exclusive. In this case whether it is a service conductor or a feeder conductor does not matter...