GEC for 100A Sub Panel Size.

[wrobotronic]

Hello,
What size conductor should be connected to a ufer in a new garage that is being fed by a 100A sub panel? And what code section would one look to for that sizing?

I have two answers from two different people and just wanted the forums opinion.

Thank you all very much....

 

[Ponchik]

Have you looked under 250.66?

 

[petersonra]

Hello,
What size conductor should be connected to a ufer in a new garage that is being fed by a 100A sub panel? And what code section would one look to for that sizing?

I have two answers from two different people and just wanted the forums opinion.

Thank you all very much....

I will give you a similar hint as the other poster did by asking some questions of you.

what is the maximum size GEC ever required for a GEC connecting to a Ufer?

is there anything in the code that would allow you to reduce the GEC size from the maximum size required for a Ufer?

 

[david]

What size feeder conductors where used to supply the garage?

250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).
(E) Grounding Electrode Conductor. The size of the grounding electrode conductor to the grounding electrode(s) shall not be smaller than given in 250.66, based on the largest ungrounded supply conductor. The installation shall comply with Part III of this article.


edit: Assuming this is a detached garage, you really didn’t say that.

 

[wrobotronic]

yes it is a detached garage.

I think based on 250.66 it should be a #8 copper.

The garage is being fed with #2 Aluminum.

 

[Ponchik]

yes it is a detached garage.

I think based on 250.66 it should be a #8 copper.

The garage is being fed with #2 Aluminum.

I have two answers from two different people

what answers did you get?

 

[david]

yes it is a detached garage.

I think based on 250.66 it should be a #8 copper.

The garage is being fed with #2 Aluminum.

"Grounding electrode conductors smaller than 6 AWG"

250.64 Grounding Electrode Conductor Installation.
( B) Securing and Protection Against Physical Damage. Where exposed, a grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried.

A 4 AWG or larger copper or aluminum grounding electrode conductor shall be protected where exposed to physical damage.

A 6 AWG grounding electrode conductor that is free from exposure to physical damage shall be permitted to be run along the surface of the building construction without metal covering or protection where it is securely fastened to the construction; otherwise, it shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor.

Grounding electrode conductors smaller than 6 AWG shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor.

 

[wrobotronic]

what answers did you get?[/QUOTE]

one person said it should be a #4 Cu based on 250.52a3 (which I think is the wrong reference)

the other person says it should be a #8 Cu based on 250.32e which I think is correct.

 

[david]

The particle answer would be #6 AWG copper based on 250.64 and 250.66

 

[infinity]

yes it is a detached garage.

I think based on 250.66 it should be a #8 copper.

The garage is being fed with #2 Aluminum.

That's the correct size. As stated it would require protection so if it were me I would use #6.