# code question



## AFOREMA1 (Nov 23, 2009)

For a 800a service running 6 thhn conducters in parallel in a single pipe find the following
1. Minimum size of conductors
2. Minimum size Pvc conduit
3. Size of GEC
Using 2008 NEC please state code references for each


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## 360max (Jun 10, 2011)

AFOREMA1 said:


> For a 800a service running 6 thhn conducters in parallel in a single pipe find the following
> 1. Minimum size of conductors
> 2. Minimum size Pvc conduit
> 3. Size of GEC
> Using 2008 NEC please state code references for each


....if you are running #6 wires in parallel for a 800a service, I suggest you find another trade/job.


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## 480sparky (Sep 20, 2007)

What do YOU get for an answer?


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## AFOREMA1 (Nov 23, 2009)

360max said:


> ....if you are running #6 wires in parallel for a 800a service, I suggest you find another trade/job.


6 conductors not # 6. 2 wires to each phase 3ph system forgot to state that. Why would I ask you to find minimum conductor size if I told you #6 conductors? Doesn't make much sense does it?:no:


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## 480sparky (Sep 20, 2007)

The answer is: Incalculable. Is it a single-phase service, or a three-phase service? Knowing that will determine the total number of conductors, hence the size of each required, followed by the size of raceway.


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## AFOREMA1 (Nov 23, 2009)

480sparky said:


> The answer is: Incalculable. Is it a single-phase service, or a three-phase service? Knowing that will determine the total number of conductors, hence the size of each required, followed by the size of raceway.


3 ph just corrected that and there are 6 conductors 2 to each phase.


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## don_resqcapt19 (Jul 18, 2010)

AFOREMA1 said:


> 3 ph just corrected that and there are 6 conductors 2 to each phase.


with or without a grounded conductor? if there is a grounded conductor is it "current carrying"?


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## 480sparky (Sep 20, 2007)

AFOREMA1 said:


> 3 ph just corrected that and there are 6 conductors 2 to each phase.



Jeez... I was working on 6 per phase. 


Is there no noodle on this service now?


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## AFOREMA1 (Nov 23, 2009)

480sparky said:


> Jeez... I was working on 6 per phase.
> 
> 
> Is there no noodle on this service now?


Is a test question not a real service from my masters exam just want to see what you guys come up with.

Oh and make sure you got all conductors are in one conduit. That makes a difference


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## 480sparky (Sep 20, 2007)

Oh, and the GEC thing...........

Rod? Pipe? Water line? CCE?


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## AFOREMA1 (Nov 23, 2009)

don_resqcapt19 said:


> with or without a grounded conductor? if there is a grounded conductor is it "current carrying"?


Nope no grounded conducted just 6 hots


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## AFOREMA1 (Nov 23, 2009)

480sparky said:


> Oh, and the GEC thing...........
> 
> Rod? Pipe? Water line? CCE?


Assume pipe.


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## 480sparky (Sep 20, 2007)

Well, assuming there's no neutral, you got 6 CCCs. That puts you into the 80% column per 310.15.(B)(2)(a).

So going to 310.16, I need to find 800/2/0.8 ampacity, and that throws me to 700s for THHN. Six 700's will fit into a 5" PVC per Table C.10(A).

Water pipe ground would be #3/0 per T250.66, pipe electrode would be #6 (250.66(A)).

Keep in mind, it's midnight here.


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## Magnettica (Jan 23, 2007)

480sparky said:


> Well, assuming there's no neutral, you got 6 CCCs. That puts you into the 80% column per 310.15.(B)(2)(a).
> 
> So going to 310.16, I need to find 800/2/0.8 ampacity, and that throws me to 700s for THHN. Six 700's will fit into a 5" PVC per Table C.10(A).
> 
> ...


Looks good. :thumbsup:

It's good to see challenging questions like these to keep it fresh. 

Then again, running these conductors in parallel in a single conduit doesn't make much business sense. :no:


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## HARRY304E (Sep 15, 2010)

Magnettica said:


> Looks good. :thumbsup:
> 
> It's good to see challenging questions like these to keep it fresh.
> 
> Then again, running these conductors in parallel in a single conduit doesn't make much business sense. :no:





> Then again, running these conductors in parallel in a single conduit doesn't make much business sense.


True,,.that would almost impossibe to pull in one pipe..

But he said it is a test question on his Master exam.


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## tkb (Jan 21, 2009)

Seems like he just wants the answers to his test questions and doesn't want to do any of the work.


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## sparky970 (Mar 19, 2008)

AFOREMA1 said:


> For a 800a service running 6 thhn conducters in parallel in a single pipe find the following
> 1. Minimum size of conductors
> 2. Minimum size Pvc conduit
> 3. Size of GEC
> Using 2008 NEC please state code references for each


What voltage?


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## 480sparky (Sep 20, 2007)

sparky970 said:


> What voltage?



Given it's THHN, it's 600 or less. :whistling2:


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## AFOREMA1 (Nov 23, 2009)

tkb said:


> Seems like he just wants the answers to his test questions and doesn't want to do any of the work.


Yeah becuase I'm in a hick state with a take home test:whistling2:

Maybe your not answering becuase you have no clue. See I can say stupid stuff about people I don't know just like you. Thanks for the help.


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## AFOREMA1 (Nov 23, 2009)

480sparky said:


> Given it's THHN, it's 600 or less. :whistling2:


You arrived at 700kcmil but on the test the options were 350,400,500, & 600 kcmil. Maybe the question was missing some info? It was on the masters and they will not allow a review of questions so not sure what they came out with for an answer.

If they had used 2 conduits no adjustment would apply and 600 would work unless the test writers messed up and thought thhn that they could use the 90 degree column . Have to try talking to the electrical board again to get them to review this question and a couple others. 
Thanks for everyones replies just wanted to make sure it wasn't my formulas that were off on this.


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## AFOREMA1 (Nov 23, 2009)

What about since they were stated to be thhn you could use the 90 degree column to get2 600 kcmil per leg at 475a*2*.8= 760a its an 800a or less main so you can go up to the 800 from 760 legally correct?

But then the actual load could not exceed the calculation using the 70 degree column which would be 672a. This would meet code correct?


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## tkb (Jan 21, 2009)

AFOREMA1 said:


> Yeah becuase I'm in a hick state with a take home test:whistling2:
> 
> Maybe your not answering becuase you have no clue. See I can say stupid stuff about people I don't know just like you. Thanks for the help.


Instead of asking for answers, why don't you tell us what you figured and we could help you. 

You have to put some effort into your test and not try to cheat.


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## 480sparky (Sep 20, 2007)

AFOREMA1 said:


> You arrived at 700kcmil but on the test the options were 350,400,500, & 600 kcmil............


For crying out loud........... every time someone posts something, you change the parameters. First you fail to post 1- or 3-phase, then no neutral. Now you're *finally* telling us the four choices available to YOU but not US!
















What's next? It's underground, and we can't use the THHN rating? Can we assume THWN-2 is acceptable or are we going to have a THWN bomb dropped on us? Or will the run be 1500' and we then must figure in 2%/3% voltage drop? Or will the PVC be on the rooftop?


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## AFOREMA1 (Nov 23, 2009)

tkb said:


> Instead of asking for answers, why don't you tell us what you figured and we could help you.
> 
> You have to put some effort into your test and not try to cheat.


1. I already took the test or I would not have the question. Therefore I could not cheat nor would I want to so please do not imply that is what I am doing. And I studied for 7 months so I put in plenty of effort. And if you go back a couple posts you will see what I was asking based on the answers provided on the test which did not match 480's answer or the one I came up with for the test. 

So again thanks for any help you can provide on the question.


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## AFOREMA1 (Nov 23, 2009)

480sparky said:


> For crying out loud........... every time someone posts something, you change the parameters. First you fail to post 1- or 3-phase, then no neutral. Now you're *finally* telling us the four choices available to YOU but not US!
> 
> 
> 
> ...


Your answer was not close to what was offered neither was mine that is why iI left them off so someone would solve it and verify what I got not try to solve to fit one of the test answers. To verify what I calculated to try to solve it. 
Now you have their answers and my worked out answer to how they may have arrived at a set of 600's or less what do you think.


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## tkb (Jan 21, 2009)

AFOREMA1 said:


> 1. I already took the test or I would not have the question. Therefore I could not cheat nor would I want to so please do not imply that is what I am doing. And I studied for 7 months so I put in plenty of effort. And if you go back a couple posts you will see what I was asking based on the answers provided on the test which did not match 480's answer or the one I came up with for the test.
> 
> So again thanks for any help you can provide on the question.


Then why did you say it was a take home test?


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## AFOREMA1 (Nov 23, 2009)

tkb said:


> Then why did you say it was a take home test?


Never said it was a take home test reread the hick and whistling smiley the sarcasm to your original comments.


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## tkb (Jan 21, 2009)

AFOREMA1 said:


> Never said it was a take home test reread the hick and whistling smiley the sarcasm to your original comments.


To me, the whistling smiley meant you were cheating on the test.

I come up with 700kcm. In 5" PVC w a 3/0 EGC.


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## 480sparky (Sep 20, 2007)

AFOREMA1 said:


> Your answer was not close to what was offered ............



So 700 is 'not close' to 600? :001_huh: How much 'closer' can I get and still be 'wrong' ?


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## AFOREMA1 (Nov 23, 2009)

tkb said:


> To me, the whistling smiley meant you were cheating on the test.
> 
> I come up with 700kcm. In 5" PVC w a 3/0 EGC.


Nope no cheating not my way. that was what I got and 480 got also, I posted the choices on the test a few posts up as well as a possible way they calculated since no load was stated. Check my hypothesis and their answers out above and let me know what you think please.


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## AFOREMA1 (Nov 23, 2009)

480sparky said:


> So 700 is 'not close' to 600? :001_huh: How much 'closer' can I get and still be 'wrong' ?


You got as close as I did I chose 600 since it was the closest to my answer but do not like it when I do no get the a match between my answer and theirs. 

Did you read my hypothesis on how they may have solved it since they did not give a load? Please look at it and tell me what you think. It's a few posts back up


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## tkb (Jan 21, 2009)

480sparky said:


> So 700 is 'not close' to 600? :001_huh: How much 'closer' can I get and still be 'wrong' ?


I change my answer to 600kcm.
Breaker can be upsized to 800 per 240.4(B).


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## AFOREMA1 (Nov 23, 2009)

tkb said:


> 600 would be wrong. The total ampacity cannot be less than 800 amps per 240.4(C).


That would not apply. It only applies to overcurrent devices over 800a.
800a and less are covered by 240.4(B)1-3


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## 480sparky (Sep 20, 2007)

Well, given the fact that we've been provided with the 'question' strung out between 4-5 posts, I think I'm gonna punch out. God knows what else there is to this 'question'.








​


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## AFOREMA1 (Nov 23, 2009)

480sparky said:


> Well, given the fact that we've been provided with the 'question' strung out between 4-5 posts, I think I'm gonna punch out. God knows what else there is to this 'question'.
> 
> 
> 
> ...


:no: you shouldn't need their answers to solve the problem they are not relevant until the end unless your guessing. If your math and theory is right your answer should be one of the choices. But thanks for confirming my original math matched yours.


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## tkb (Jan 21, 2009)

AFOREMA1 said:


> That would not apply. It only applies to overcurrent devices over 800a.
> 800a and less are covered by 240.4(B)1-3


I changed to 600kcmil. See my edited post.


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## AFOREMA1 (Nov 23, 2009)

tkb said:


> I changed to 600kcmil. See my edited post.


I agree 600 is probably the answer but the next size up breaker after calculating with the correct column is a 700a breaker not 800 unless my calculations from post 21 is correct and code compliant. I need to be sure of the why of how they got it not just what the probable answer is.


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## tkb (Jan 21, 2009)

AFOREMA1 said:


> I agree 600 is probably the answer but the next size up breaker after calculating with the correct column is a 700a breaker not 800 unless my calculations from post 21 is correct and code compliant. I need to be sure of the why of how they got it not just what the probable answer is.


600 kcmil @ 90c is 474 amps

475 amps * 2 = 950 amps

950 amp @ 80% for 4-6 CCC in conduit = 760 amps @ 90c

760 amps / 2 = 380 amps

600kcmil is good for 430 amps @ 75c per 310.15(B)

430 amps * 2 = 860 amps


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## Magnettica (Jan 23, 2007)

tkb said:


> 600 kcmil @ 90c is 474 amps
> 
> 475 amps * 2 = 950 amps
> 
> ...


So all your lugs and everything are rated for 90º? :whistling2:


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## tkb (Jan 21, 2009)

Magnettica said:


> So all your lugs and everything are rated for 90º? :whistling2:


I used the 75c rating for my final rating. 
Look at my calc again.


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## Salvatoreg02 (Feb 26, 2011)

6-xhhw-2 600MCM in a 4" PVC sch40 or HPDE conduit
Since a ConEd approved 400amp meter pan is only rated for 380 amps I will assume a 800amp Meter pan has a lower ampacity as well. With that said, 600mcm is rated for 475x.80%=380x2=760
Up size breaker to 800amps which is allowed. 
FINAL ANSWER 6-600MCM XHHW-2 90degree's FROM METER PAN TO FIRST MEANS OF DISCONNECT.

Sent from my iPhone using ET Forum


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## tkb (Jan 21, 2009)

Salvatoreg02 said:


> 6-xhhw-2 600MCM in a 4" PVC sch40 or HPDE conduit
> Since a ConEd approved 400amp meter pan is only rated for 380 amps I will assume a 800amp Meter pan has a lower ampacity as well. With that said, 600mcm is rated for 475x.80%=380x2=760
> Up size breaker to 800amps which is allowed.
> FINAL ANSWER 6-600MCM XHHW-2 90degree's FROM METER PAN TO FIRST MEANS OF DISCONNECT.
> ...


I never saw an 800 amp meter socket before, and with 90ºc terminations at that.

You would need a CT cabinet and use 75ºc column for the final rating.
I agree at 600kcmil, but at 860 amps using 430*2.

Also PVC40 or HDPE would require 5" for 6-600kcmil.


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## AFOREMA1 (Nov 23, 2009)

I'm thinking since it is being derated that 
1. They used the 90 column for the thhn value.
2. And looking at my new Tom Henry book using it may be correct since the wires are being created.


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