250.122 Size of Equipment Grounding Conductors

[Son]

Please, explain the below example. This is example in 250.122 Size of Equipment Grounding Conductors (G)

I do not understand "a 600-kcmil copper conductor is tapped to a 1200-ampere feeder and supplies a fusible switch with 400-ampere fuses."

is it "is tapped to" or "is tapped from" ? I can not image the wiring diagram although I understand the choice.

"For example, a 600-kcmil copper conductor is tapped to a 1200-ampere feeder and supplies a fusible switch with 400-ampere fuses. Where the 400-ampere overcurrent protection is installed at the point the 600-kcmil conductors receive their supply, the equipment grounding conductor from Table 250.122 is a 3 AWG copper or 1 AWG aluminum conductor. However, in this tap conductor application, it is the 1200-ampere device that is on the line side of the 600-kcmil tap conductors, and the equipment grounding conductor from Table 250.122 is based on the 1200-ampere device. In this
case, the equipment grounding conductor is required to be a 3/0 AWG copper or 250-kcmil aluminum conductor. This provision applies only where a wire-type equipment grounding conductor is run with the feeder tap conductors. Other equipment grounding conductors permitted in 250.118 can also be used where they meet the requirements for tap conductor wiring methods specified in 240.21(B)(1) through 240.21(B)(5)."

Thank you and Best regards.

 

[augie47]

Please, explain the below example. This is example in 250.122 Size of Equipment Grounding Conductors (G)

I do not understand "a 600-kcmil copper conductor is tapped to a 1200-ampere feeder and supplies a fusible switch with 400-ampere fuses."

is it "is tapped to" or "is tapped from" ? I can not image the wiring diagram although I understand the choice..

I think we use the terms interchangeably.. The 600 amp feeder is CONNECTED to a 1200 amp feeder

"For example, a 600-kcmil copper conductor is tapped to a 1200-ampere feeder and supplies a fusible switch with 400-ampere fuses. Where the 400-ampere overcurrent protection is installed at the point the 600-kcmil conductors receive their supply, the equipment grounding conductor from Table 250.122 is a 3 AWG copper or 1 AWG aluminum conductor. However, in this tap conductor application, it is the 1200-ampere device that is on the line side of the 600-kcmil tap conductors, and the equipment grounding conductor from Table 250.122 is based on the 1200-ampere device. In this
case, the equipment grounding conductor is required to be a 3/0 AWG copper or 250-kcmil aluminum conductor. This provision applies only where a wire-type equipment grounding conductor is run with the feeder tap conductors. Other equipment grounding conductors permitted in 250.118 can also be used where they meet the requirements for tap conductor wiring methods specified in 240.21(B)(1) through 240.21(B)(5)."

Thank you and Best regards.

The EGC would be sized based on the protection ahead of the feeders. A 3/0 EGC would be needed until the 400 amp fuses. After that point a #3 would be sufficient.

 

[Son]

Thank you very much.

_____________________________
"We learn not at school but in life"

 

[infinity]

The EGC would be sized based on the protection ahead of the feeders. A 3/0 EGC would be needed until the 400 amp fuses. After that point a #3 would be sufficient.

Agreed and one other thing to note the EGC does not have to be sized larger than the tap conductors. For the 10' tap rule this might come into play quite often.

 

[Son]

Yes. I shall note.

Thank you.

 

[jumper]

Please, explain the below example. This is example in 250.122 Size of Equipment Grounding Conductors (G)

I do not understand "a 600-kcmil copper conductor is tapped to a 1200-ampere feeder and supplies a fusible switch with 400-ampere fuses."

is it "is tapped to" or "is tapped from" ? I can not image the wiring diagram although I understand the choice.

How about a picture?

 

[jumper]

Here is a similar thread.

 

[Son]

I have read that thread already. But it does not explain that I ask.

I just confuse "is tapped to" with "is tapped from".

Thank you for your support.

 

[augie47]

perhaps it depends on which conductor you are viewing.
If you consider the 1200 amp conductor, the 400 amp one is "tapped from it". If you consider the 400 amp conductor, it is "tapped to" the larger one.
I believe its simply semantics... in the end one conductor of less ampacity is connected to one of larger ampacity,
Take a look at the definition of a "Tap Conductor" in 240.2 and see if that helps.

 

[Son]

Thank you augie47.