# What size conductor?



## Dennis Alwon (May 9, 2009)

This is hypothetical. Not a hard question but very curious one, IMO


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## jwjrw (Jan 14, 2010)

Uh.....unless I am missing something....400mcm Copper is good for 335 amps which is less than your calculated load so I don't think you can use it. A 500mcm Copper is good for 380 so I would pick it but it is not a choice...:blink:


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## Wirenuting (Sep 12, 2010)

B @ 600kcm


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## Dennis Alwon (May 9, 2009)

jwjrw said:


> Uh.....unless I am missing something....400mcm Copper is good for 335 amps which is less than your calculated load so I don't think you can use it. A 500mcm Copper is good for 380 so I would pick it but it is not a choice...:blink:


Read the question again carefully-- residence 400 amps TW wire 350 amp load.

After you do it for 2008 then do it for 2011.


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## Dennis Alwon (May 9, 2009)

Wirenuting said:


> B @ 600kcm


Which code cycle?


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## NolaTigaBait (Oct 19, 2008)

I say 600 also...On the 08....Who uses TW anymore? What a bogus question.. It doesn't say 400 amp ocp, just 400 amp service...


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## Dennis Alwon (May 9, 2009)

NolaTigaBait said:


> I say 600 also...On the 08....Who uses TW anymore? What a bogus question.. It doesn't say 400 amp ocp, just 400 amp service...


It is bogus- but a 400 amp service with a calculated load of 350 needs to be 700 KCM in 2011. I find it interesting because if THW were used we could use T. 310.15(B)(7) (2011) at 400 Kcm. That is an incredible difference.

Why do manufacturers even make TW or do they???? Maybe the column is there for the old wires.


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## NolaTigaBait (Oct 19, 2008)

Dennis Alwon said:


> It is bogus- but a 400 amp service with a calculated load of 350 needs to be 700 KCM in 2011. I find it interesting because if THW were used we could use T. 310.15(B)(7) (2011) at 400 Kcm. That is an incredible difference.
> 
> Why do manufacturers even make TW or do they???? Maybe the column is there for the old wires.


Is 310.15b7 equivalent to 310.15b6? in the 08?


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## Dennis Alwon (May 9, 2009)

NolaTigaBait said:


> Is 310.15b7 equivalent to 310.15b6? in the 08?


Yes, ...........


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## Wirenuting (Sep 12, 2010)

Dennis Alwon said:


> Which code cycle?


08 and as referenced in the Ugly's book. 

We still have alot of TW feeders here. 500 is the biggest I've seen before paralleling.
We don't install it, but we use existing when possible.


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## Jlarson (Jun 28, 2009)

Anytime I see a question like that, that involves TW I know there is a pretty good chance of it being bogus. 

I would have said 600 BTW.


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## Wirenuting (Sep 12, 2010)

Dennis Alwon said:


> It is bogus- but a 400 amp service with a calculated load of 350 needs to be 700 KCM in 2011. I find it interesting because if THW were used we could use T. 310.15(B)(7) (2011) at 400 Kcm. That is an incredible difference.
> 
> Why do manufacturers even make TW or do they???? Maybe the column is there for the old wires.


So the correct answer for a single phase service in 08 & 11 is C?


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## Dennis Alwon (May 9, 2009)

Jlarson said:


> Anytime I see a question like that, that involves TW I know there is a pretty good chance of it being bogus.
> 
> I would have said 600 BTW.


The question was really just entertaining the change from 2008 to 2011 ampacity and the difference in conductor size the TW would make in this unusual situation.


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## I_get_shocked (Apr 6, 2009)

Dennis Alwon said:


> It is bogus- but a 400 amp service with a calculated load of 350 needs to be 700 KCM in 2011. I find it interesting because if THW were used we could use T. 310.15(B)(7) (2011) at 400 Kcm. That is an incredible difference.
> 
> Why do manufacturers even make TW or do they???? Maybe the column is there for the old wires.



If you size the service conductors based on the load calculation of 350A, are you using a 400A OCPD based on 240.4 b?

What is the difference between the 08 and 2011 code cycles as I see using 600kcmil as an option for a TW conductor under 2011. Is there another option under the 08? I see that the 600kcmil TW and its 350A rating is shaded and new to 2011

Thanks


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## Dennis Alwon (May 9, 2009)

I_get_shocked said:


> If you size the service conductors based on the load calculation of 350A, are you using a 400A OCPD based on 240.4 b?
> 
> What is the difference between the 08 and 2011 code cycles as I can only see using 700kcmil as an option fora TW conductor. Is there another option under the 08?
> 
> Thanks


I probably should have stated 400 amp breaker but under the 2008 the ampacity of 600 kcm is 355amps which would allow you to use 400 amp breaker based on 240.4(B) & 240.6


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## Dennis Alwon (May 9, 2009)

Wirenuting said:


> So the correct answer for a single phase service in 08 & 11 is C?


In 2008 it would be 600 amps but in 2011 it would be 700 amps.


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## Wirenuting (Sep 12, 2010)

Dennis Alwon said:


> In 2008 it would be 600 amps but in 2011 it would be 700 amps.


Ok. Thanks.


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## I_get_shocked (Apr 6, 2009)

Dennis Alwon said:


> In 2008 it would be 600 amps but in 2011 it would be 700 amps.


So because 600kcmil is only rated for 350A in 2011 and 350A is a standard breaker size, it cannot be protected by a 400A ocpd and hence cannot be used on a 400A service, correct?


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## Dennis Alwon (May 9, 2009)

I_get_shocked said:


> So because 600kcmil is only rated for 350A in 2011 and 350A is a standard breaker size, it cannot be protected by a 400A ocpd and hence cannot be used on a 400A service, correct?


That is correct.


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## RAHARRIS78 (Oct 13, 2011)

since you have a 400a service i presume your going to have two 200a main brkr panels with parrell 4/0AL or 30CU.


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