tap rule clarification

[david]

I need you to refresh my memory concerning tap rule.

400 amp single phase service for a commercial building. 400 amp main fused disconnect is the first overload protection. I need to tap the 400 amp d/s to install a 200 amp fused disconnect downstream. What is the furthest the 200 amp d/s can be located from the 400 amp d/s?

Many thanks.

Since you're using a 200 amp tap to a 400 amp feeder you can use the 25' tap rule which for the tap conductors is 1/3 the ampacity of the OCPD ahead of the tap. This is assuming that your tap will be on the load side of the service disconnect.

see post #3
You say you need to tap a 400 amp main service fused disconnect, are you tapping the line or load side of the service disconnect?

Since you are asking about the tap rule that implies the load side of the service disconnect just wanted you to clarify that, if you would be asking about the line side you will get a different answer.

 

[hardworker]

see post #3
You say you need to tap a 400 amp main service fused disconnect, are you tapping the line or load side of the service disconnect?

Since you are asking about the tap rule that implies the load side of the service disconnect just wanted you to clarify that, if you would be asking about the line side you will get a different answer.

I am tapping the load side.

 

[infinity]

I am tapping the load side.

Tap conductors up to 25' with a minimum of 1/3 the ampacity of the 400 amps. That's it.