jljones
Member
- Location
- Pennsylvania
In an 800 amp service which is fed with (2) 500 MCM parallel conductors per phase. How would I calculate my grounding electrode conductor?
parllel conductors
- Thread starter jljones
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jljones
Member
- Location
- Pennsylvania
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.
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.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Add the two parallel conductors together and then look at 250.66.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
jljones
Member
- Location
- Pennsylvania
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:
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:
- Location
- Massachusetts
Thats OK, I can not for the life of me figure out why it would make a difference. 
Hopefully Larry will explain.
Hopefully Larry will explain.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
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.
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).
jljones
Member
- Location
- Pennsylvania
Parallel Conductors
Parallel Conductors
Thanks everyone for your help and Augie47 thank you for your explanation of the print under the table.
Parallel Conductors
Thanks everyone for your help and Augie47 thank you for your explanation of the print under the table.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Would you believe just making conversation? :roll:Thats OK, I can not for the life of me figure out why it would make a difference.
Hopefully Larry will explain.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
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.
Welcome to the forum.
800CM
Member
- Location
- Corning CA Family Farm since 1942
"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
"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.
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.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
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.
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.
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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