Does tap rule apply to the disconnect also?

[Matt Donovan]

I am tapping off an 800A feeder (2x 600mcm) to a 600A disconnect. I would have used 2x 350mcm (sized for 600A), but the tap is over 25ft so I am planning to use 2x 600mcm (sized for 800A) for the tap conductors. Is it OK to terminate on a 600A disconnect with 600A fuses? Or do I need to terminate on an 800A disconnect with 600A fuses? The second option seems silly, but some people think that if the tap conductors needed to be sized for 800A, then the bus they land on must be sized for 800A also. Is this addressed in the code?

 

[david luchini]

I am tapping off an 800A feeder (2x 600mcm) to a 600A disconnect. I would have used 2x 350mcm (sized for 600A), but the tap is over 25ft so I am planning to use 2x 600mcm (sized for 800A) for the tap conductors. Is it OK to terminate on a 600A disconnect with 600A fuses? Or do I need to terminate on an 800A disconnect with 600A fuses? The second option seems silly, but some people think that if the tap conductors needed to be sized for 800A, then the bus they land on must be sized for 800A also. Is this addressed in the code?

You don't have tap conductors at all. You can land the 800A feeder on the 600A switch if they will fit.

 

[petersonra]

I am tapping off an 800A feeder (2x 600mcm) to a 600A disconnect. I would have used 2x 350mcm (sized for 600A), but the tap is over 25ft so I am planning to use 2x 600mcm (sized for 800A) for the tap conductors. Is it OK to terminate on a 600A disconnect with 600A fuses? Or do I need to terminate on an 800A disconnect with 600A fuses? The second option seems silly, but some people think that if the tap conductors needed to be sized for 800A, then the bus they land on must be sized for 800A also. Is this addressed in the code?

The code does not care. You can terminate the conductors sized for 800 A on the 600 A disconnect, assuming the wires will fit on the lugs.

I think i would get an 800 A disconnect with 800 A fuses since the expensive part is upsizing the conductors. I don't know what it is you are feeding downstream of the disconnect but most cases this arrangement would work fine and give you some flexibility going forward.

 

[don_resqcapt19]

The code does not care. You can terminate the conductors sized for 800 A on the 600 A disconnect, assuming the wires will fit on the lugs.

I think i would get an 800 A disconnect with 800 A fuses since the expensive part is upsizing the conductors. I don't know what it is you are feeding downstream of the disconnect but most cases this arrangement would work fine and give you some flexibility going forward.

He could use the 601 amp fuses in the 800 amp disconnect.