GEC sizing to a ground rod

Status
Not open for further replies.
X

xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
Hello,
So, sizing the GEC to a ground rod only requires the GEC to be a #6 AWG? My understanding is that the GEC was sized off of table 250.66 as per 250.66. but 250.66A seems to negate 250.66. Am I missing something here?
 
I fail to see the conflict, 250.66 states to use Table 250.66 except as permitted (A)-(C) and "A" allows the #6 provided the provisions are met.
 
augie47 said:
I fail to see the conflict, 250.66 states to use Table 250.66 except as permitted (A)-(C) and "A" allows the #6 provided the provisions are met.
Click to expand...
I am looking at the 2020 handbook exhibit 250.30, which describes to do otherwise.
 
xformer said:
Hello,
So, sizing the GEC to a ground rod only requires the GEC to be a #6 AWG? My understanding is that the GEC was sized off of table 250.66 as per 250.66. but 250.66A seems to negate 250.66. Am I missing something here?
Click to expand...


Think of (A) as an exception to T. 250.66. There is other exceptions also as in CEE
 
xformer said:
I am looking at the 2020 handbook exhibit 250.30, which describes to do otherwise.
Click to expand...
What does is say specifically?
2020 NEC:

250.66 Size of Alternating-Current Grounding Electrode Conductor.
The size of the grounding electrode conductor at the service, at each building or structure where supplied by a feeder(s) or branch circuit(s), or at a separately derived system of a grounded or ungrounded ac system shall not be less than given in Table 250.66, except as permitted in 250.66(A) through (C).
Click to expand...

250.66(A) Connections to a Rod, Pipe, or Plate Electrode(s).
If the grounding electrode conductor or bonding jumper connected to a single or multiple rod, pipe, or plate electrode(s), or any combination thereof, as described in 250.52(A)(5) or (A)(7), does not extend on to other types of electrodes that require a larger size conductor, the grounding electrode conductor shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.
Click to expand...
 
I second Rob's question, what is the actual wording?
 
From the Handbook... Exhibit 250.30 next to last sentence. "If the GEC is run to the Ground rod first, and then to the waterpipe, the GEC is required to be sized based upon Table 250.66 as if it were run to the water pipe electrode."
 
xformer said:
From the Handbook... Exhibit 250.30 next to last sentence. "If the GEC is run to the Ground rod first, and then to the waterpipe, the GEC is required to be sized based upon Table 250.66 as if it were run to the water pipe electrode."
Click to expand...


Yes that is true. Because the water pipe requires a #4 for instance, you cannot hit the ground rod with a smaller conductor then what the pipe requires. If nothing is connected past the rod then #6 is all that is required.
 
xformer said:
From the Handbook... Exhibit 250.30 next to last sentence. "If the GEC is run to the Ground rod first, and then to the waterpipe, the GEC is required to be sized based upon Table 250.66 as if it were run to the water pipe electrode."
Click to expand...
It says that clearly in 250.66(A).

250.66(A) Connections to a Rod, Pipe, or Plate Electrode(s).

If the grounding electrode conductor or bonding jumper connected to a single or multiple rod, pipe, or plate electrode(s), or any combination thereof, as described in 250.52(A)(5) or (A)(7), does not extend on to other types of electrodes that require a larger size conductor, the grounding electrode conductor shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.
Click to expand...
 
That is what I stated in the last post. Since the bonding jumpers require #4 then grounding electrode conductor must be sized to the largest bonding jumper. You can't expect #6 from the panel to handle a #4 so in this case you would have to run #4 to the rod
 
Dennis Alwon said:
Yes that is true. Because the water pipe requires a #4 for instance, you cannot hit the ground rod with a smaller conductor then what the pipe requires. If nothing is connected past the rod then #6 is all that is required.
Click to expand...
Why does the water pipe require a #4? Doesn't 250.66A come into play again as connection to a rod, pipe, or plate electrode? I am not trying to play devils advocate here. just trying to further understand. :) I feel I am thinking way too hard on this and perhaps should just drink my coffee. :coffee::)
 
xformer said:
Why does the water pipe require a #4? Doesn't 250.66A come into play again as connection to a rod, pipe, or plate electrode? I am not trying to play devils advocate here. just trying to further understand. :) I feel I am thinking way too hard on this and perhaps should just drink my coffee. :coffee::)
Click to expand...
It's confusing but the pipe in 250.66(A) is not a water pipe electrode. It's a piece of pipe used like grounding rod.
 
Status
Not open for further replies.
Top