parllel conductors

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As a general rule we don't "answer" questions for students but try to provide direction. Take a look at 250,66 and tell us what size you think it should be
 
Parllel conductors

Parllel conductors

Thanks for your reply and I have looked at 250.66. According to the table it should be 1/0 copper for 500 MCM, what I wasn't sure of if I had to add the two conductors togeather for a total 1000 MCM. In that case the grounding electrode would need to be a 2/0 AWG.

thank you for not just giving me the answer, I am a 52 year old laidoff construction project manager who came up through the field and worked my way up. I have done electric work for the past twenty five years, but I never had to figure any of this stuff out for myself.

Thanks again for your help.
 
Parallel Conductors

Parallel Conductors

This assignment is based on the 2008 code. and there is no mention of one or two raceways. So I will assume only one. I know its not good to assume.:grin:
 
jljones said:
This assignment is based on the 2008 code. and there is no mention of one or two raceways. So I will assume only one. I know its not good to assume.:grin:
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Not that it matters in answering a question about the GEC, but given the service size and the conductor size it actually cannot be in one raceway.
 
jljones said:
Thanks for your reply and I have looked at 250.66. According to the table it should be 1/0 copper for 500 MCM, what I wasn't sure of if I had to add the two conductors together for a total 1000 MCM. In that case the grounding electrode would need to be a 2/0 AWG.

thank you for not just giving me the answer, I am a 52 year old laidoff construction project manager who came up through the field and worked my way up. I have done electric work for the past twenty five years, but I never had to figure any of this stuff out for myself.

Thanks again for your help.
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I appreciate your situation and admire you for your effort.
You are in the correct location. Check the "Notes" under the Table.
The Code never "speaks" like we do :). It doesn't mention parallel raceways as it's not important here for your question. It does state "multiple sets of service conductors" (raceway or other) and tells you to use the sum. So 1,000 kcmil would be correct, calling for a 2/0 grounding electrode,
With that in mind, note there are exceptions to the 2/0 in250.66(B) and 250.66(A).
 
This would not likely be part of a test question, but let me add that a pair of 500's might not be adequate for a service of 800 amps. Several factors might be relevant. Top of the list would be the calculated load. A 500 MCM copper conductor is only good for 380 amps, so a pair of them are good for 760. If the calculated load is less than that, then you can use a pair of 500's and protect them at 800 amps. If the calculated load is more than 760 amps, or if no calulation was performed, such that we have to presume that the load could be as high as 800 amps, then you cannot use a pair of 500's.

Welcome to the forum.
 
"without a splice or joint"

"without a splice or joint"

From Code section 250.66 and regarding: : "the common grounding electrode conductor remains without a splice or joint"

QUESTION
Does terminating the ground electrode conductor from two service entrance neutral lugs to a copper bus bar (with correctly applied T&B compression terminals) , from which connections are made in the same manner to approved grounding rods, meet the "without a splice or joint" requirement?

Plan to use two each 2/0 stranded attached to the 400A Service Entrance switch neutral . Then to the 12" x 4" x 1/4" tin plated copper bus bar. Then running 2 each 2/0 stranded to 2 each stainless steel rods 10" x 3/4" spaced 12 - 16' apart.
Also will attach a 2/0 to the deep well hard steel (will not rust) 12" Dia x 50 feet casing.

Perhaps overkill but at age 82 I am of the old school. All wire is left over form my more active days in electrical work. 2 each 2/0 = .7296" Dia which is only .0834" smaller than the 500mcm (.8130" Dia) feeder wires (if my calculations are correct).

Will use my T&B TBM6S Shure-Stake crimper with T&B
connectors.

I should not be sitting at the computer so long but read through the forum for a couple of hours tonight. Enjoyable, like being in a library. Thanks so much for all who share their experiences. I have not had a copy of the code for many years... which reminds me, when I started, the code would fit into my breast pocket and I knew almost every word. One Forum Member's bottom line is very enjoyable.
Paraphrased: I am not old, I started in knob and tube.
Yep, I actually did start in knob and tube in San Francisco at age 15.

"Those were the good old days" but not as exciting as these days with so many good products which I wish that I had had in bygone years.

Thanks and appreciation,

800CM
aka Marshall
WW2 Vet = getting old :)
Tired but not retired farmer

I use to be steady on my feet and strong
I am still strong
But my deodorant takes care of it
 
Originally you spoke of an 800 amp service with two parallel conductors per phase, but now you mention a 400 amp switch. Since you seem to be using "available" 2/0 conductors it makes no difference in this situation, but if the service is actually composed of (2) 400 amp switches, the GE from each switch could be reduced to 1/0.
In addition, please note that 250.66(A) allows the use of a #6 Cu as the GE to rod and pipe electrodes regardless of the service size. You can, of course, use the 2/0, but it's not necessary.
IMHO, Your installation using the common buss bar complies with 250.64(F) as long as the terminations are made by listed connector OR by exothermic means.
The plan definitely has overkill as a single 2/0 is adequate for all portions of the system and oversize for some. (250.66 list A 2/0 as adequate for up to 1100 kcmil sum service conductor).
Might I add that I admire and am a bit envious of your skills at 82 and appreciate all you have contributed to the industry.
 
augie47 said:
Originally you spoke of an 800 amp service with two parallel conductors per phase, but now you mention a 400 amp switch.
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This poster is not the one who started the thread...:grin: I took what you wrote as thinking he was the same guy. Forgive me if I misspoke.:)
 
Dennis Alwon said:
This poster is not the one who started the thread...:grin: I took what you wrote as thinking he was the same guy. Forgive me if I misspoke.:)
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I've never know you to "mis-speak". It takes all of you to keep me in line..... danged old age...
thanks, Dennis.
 
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