Clarification please

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ryan_618

ryan_618

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Location
Salt Lake City, Utah
Silly me, I thought I had a good grasp on GEC's. Reading article 250.54 makes me wonder, though. Scenario: 400A service. Available electrodes: water pipe and concrete encased. The Ufer can be used to satisfy the requirement of a supplemental electrode to the water pipe, as required by 250.53 (D)(2). A 1/0 copper was ran to the water pipe as per art.250.66 (Service entrance conductors sized per 310.15 fo residential). The conductor to the concrete encased was #6. I believe that it must be #4, as per 250.66(B).
250.50 states that if available, each electrode listed in 250.52 (A)(1)through(A)(6) shall be bonded together to form the grounding electrode system. Why does 250.54 state that a supplement grounding electrode need not be bonded in accordance with 250.50? Also see 250.53 (D)(2) which states that the GEC of the supplement shall permitted to be bonded... This seems contridicting to me. So if there were steel, ufer, water pipe, rod, pipe, plate & ring...none of them would have to be bonded together because they could all be considered supplements? Am I reading this wrong?
Also, can someone verify the sizing of the Ufer ground in the above case (#4)?
Thanks in advance for your replies.
 
Re: Clarification please

Ryan,
This is just another example of where we have to be very careful with the wording use in the NEC. "Supplemental" is used in 250.53(D)(2) and "supplementary" is used in 250.54. These are not the same. The "supplementary" grounding electrode is not required by the code and if installed is permitted to be connected to the EGC of the equipment where the supplementary electrode is installed. The bonding connections for the required supplemental grounding electrode(s) are in 250.53(D)(2) and 250.53(E).
You are correct that the maximum required size of the GEC to a concrete encased electrode is #4 copper.
Don
 
Re: Clarification please

Hello Don, and thanks for your post. When I posted this thread your name was one that I was hoping to see respond. I regret to say that this is still as clear as mud though!!! The building steel, for example, is required to be used if available, so is the water pipe. I understand to a degree what you're saying, but I wouldn't think the usage of building steel is "not required by code". With that in mind, even though it meets the criteria as a supplement to the water pipe, I would think it would need to be bonded to the other electrodes. I am surprised no one else jumped on this thread, I guess I'm the only one confused by it :confused: Thanks aagain Don.
 
Re: Clarification please

Ryan,
Check out Mike Holt's online video clips. He covers a lot of grounding & bonding issues (and a rafter of other NEC code sections). He has eleven clips alone on Article 250:

http://www.mikeholt.com/videolist.php

../Wayne C.

[ September 11, 2003, 03:16 PM: Message edited by: awwt ]
 
Re: Clarification please

Ryan,
All of the items in 250.52, including the building steel, are required to be used as grounding electrodes and they may be used to supplement the metal underground water pipe. These are all required to be bonded together. 250.54 is talking about "supplementary",(not code required) grounding electrodes. An example is a grounding electrode that is installed at a parking lot light pole. This grounding electrode is permitted to be connected to the pole equipment grounding conductor. That is the only code required bonding for these "supplementary" grounding electrodes.
Don
 
Re: Clarification please

Don, thank you very much for your reply. (wayne also). It makes perfect sense when you think of it that way, i just kept getting back to the "grounding electrode system" concept. Thanks again.
Ryan (go Utes tonight!)
 
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