What Size GEC

Ohm2

Ohm2

Member
Location
Washington
Occupation
Electrician
Ok this site has two triplex buildings. Both buildings have a ufer (rebar is 1/2in). Building 1 has the service ( 600a) and hits the ufer with a #4cu—then each unit has a #4cu to an accessible ufer. Building 1 serves the detached tri-plex ( building 2) with 1/0 1/0 2Al with a #6 EGC. Building 2 has access to the ufer ( rebar is 1/2 in) in each unit ( same as building 1). What size GEC shall be installed from the non-serviced rated panel to the ufer. Do we use T250.66 based on the largest ungrounded conductor or is it going to be a min number 4cu per 250.52(A)3. Or am I thinking too much😀
 
Ohm2 said:
Building 1 has the service ( 600a) and hits the ufer with a #4cu—then each unit has a #4cu to an accessible ufer.
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So the service has the connection of the GEC to the CEE and each individual panel within the same building connects to the CEE also in building 1?
 
Got that part my friend. The question was can building 2’s conductor from the sub-panel to the ufer be smaller than #4cu…based on the largest size ungrounded conductor, or is the minimum a #4cu?
 
Ohm2 said:
Got that part my friend. The question was can building 2’s conductor from the sub-panel to the ufer be smaller than #4cu…based on the largest size ungrounded conductor, or is the minimum a #4cu?
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Yes, so in building one each individual panel is fed by a feeder so connection to the CEE is not required but since building 2 is a separate structure connection to the CEE is required. That connection is sized based on Table 250.66 and the GEC can be smaller than #4. The #4 minimum conductor size for CEE's is when the conductor is used to make the electrode instead of using the rebar.
 
infinity said:
Yes, so in building one each individual panel is fed by a feeder so connection to the CEE is not required but since building 2 is a separate structure connection to the CEE is required. That connection is sized based on Table 250.66 and the GEC can be smaller than #4. The #4 minimum conductor size for CEE's is when the conductor is used to make the electrode instead of using the rebar.
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That’s what I thought. Thank you!
 
infinity said:
A GEC can be as small as #8. #6 and larger can be run exposed without protection when not subject to damage. #8 would always require protection.
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Yup!! Had a brain twist. Back story: Seen a detached triplex with #6cu being ran to rebar from each unit —while the triplex with the main service they installed #4. I went into overdrive wondering why ( overthinking). I came here to un-twist my mind and get back on point. ….some installs will have you second guessing…lol!!
 
Ohm2 said:
Yup!! Had a brain twist. Back story: Seen a detached triplex with #6cu being ran to rebar from each unit —while the triplex with the main service they installed #4. I went into overdrive wondering why ( overthinking). I came here to un-twist my mind and get back on point. ….some installs will have you second guessing…lol!!
Click to expand...
We typically run #6 even for a 100 amp service where #8 could be used due to the protection requirements. We've also used #6 aluminum for the same reason.
 
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