# What size wire?



## crazymurph (Aug 19, 2009)

My boss is adding on to a retail space that he owns and I am installing the service. The service is 480 V., 3 phase, 200 amp. My boss wants to use 4/0 AL. in 3" pvc conduit. I called the inspector and he sais that we need to run 250kcmil. My boss is very insistant that we can use 4/0 XHHW. What am I missing?:help:


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## BBQ (Nov 16, 2010)

crazymurph said:


> My boss is adding on to a retail space that he owns and I am installing the service. The service is 480 V., 3 phase, 200 amp. My boss wants to use 4/0 AL. in 3" pvc conduit. I called the inspector and he sais that we need to run 250kcmil. My boss is very insistant that we can use 4/0 XHHW. What am I missing?:help:


In my opinion, unless your boss has provided load calculations to the inspector showing the load is less than 180 amps (4/0 ALs rating) the inspector can insist on conductors with an ampacity exceeding 200 amps.

On the other hand if the calculated load is under 180 amps, 4/0 AL is acceptable due to 240.4(B).



> *240.4(B) Devices Rated 800 Amperes or Less. *The next higher
> standard overcurrent device rating (above the ampacity of
> the conductors being protected) shall be permitted to be
> used, provided all of the following conditions are met:
> ...


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## Dennis Alwon (May 9, 2009)

I agree with Bob and I have done this. The calculated load was 105 amps in a art gallery/ retail store so I used 4/0 on a 200 amp breaker.


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## knowshorts (Jan 9, 2009)

Your boss and inspector are both looking at 310.16. You boss at the 90 degree column and the inspector at the 75 degree column.


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## Dennis Alwon (May 9, 2009)

knowshorts said:


> Your boss and inspector are both looking at 310.16. You boss at the 90 degree column and the inspector at the 75 degree column.


That does not matter in this case if the calculated load is not greater than 180 amps.


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## knowshorts (Jan 9, 2009)

Dennis Alwon said:


> That does not matter in this case if the calculated load is not greater than 180 amps.


While that may be true, it was never stated in the OP. Just my guess why the 2 have different answers.


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## BBQ (Nov 16, 2010)

knowshorts said:


> While that may be true, it was never stated in the OP. Just my guess why the 2 have different answers.


Well one way assumes his boss is not sharp the other assumes the boss knows his codes.


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## Jmohl (Apr 26, 2011)

@Dennis, I know what you are saying about the calculated load and yeah, 200A breaker with a calc. load at 105 you can do 4/0, but (and this is just my thoughts) I never want to have my conductors rated at less than the rated load of my OCPD. They may have only 105 NOW, but there is no guarantee that they won't FIND 95 or so Amps of load to stick on it later..... And not every guy out there is gonna check to see that the conductors feeding the 200A Breaker are in fact, rated for 200A...


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## BBQ (Nov 16, 2010)

Jmohl said:


> I know what you are saying about the calculated load and yeah, 200A breaker with a calc. load at 105 you can do 4/0, but (and this is just my thoughts) I never want to have my conductors rated at less than the rated load of my OCPD. They may have only 105 NOW, but there is no guarantee that they won't FIND 95 or so Amps of load to stick on it later..... And not every guy out there is gonna check to see that the conductors feeding the 200A Breaker are in fact, rated for 200A...


What you choose to do is fine, we can all exceed the code and feel good about it. 

But code wise anyone adding load to a service is responsible to make sure it is adequate.

It is very common that service conductors are not rated as high the breakers in both commercial and residential, sometimes by quite a lot.

I worked on a commercial service supplied with 1200 amps of copper supplying a main lug only panel with six breakers as the service disconnecting means that added up to 3000 amps.


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## Jmohl (Apr 26, 2011)

@BBQ, yeah I see that a lot in industrial. And like I said, per code, there is nothing wrong with pulling in conductors rated at calc load vs. OCPD, but in the kind of work I do, I am always looking to the future. I take a if you build it, it will get used approach, so I generally go for more robust than absolutely needed. It helps that I don't have a penny pinching HO to sell, just a plant manager that really don't know what I'm doing anyway....:whistling2:


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## Dennis Alwon (May 9, 2009)

Jmohl said:


> @Dennis, I know what you are saying about the calculated load and yeah, 200A breaker with a calc. load at 105 you can do 4/0, but (and this is just my thoughts) I never want to have my conductors rated at less than the rated load of my OCPD. They may have only 105 NOW, but there is no guarantee that they won't FIND 95 or so Amps of load to stick on it later..... And not every guy out there is gonna check to see that the conductors feeding the 200A Breaker are in fact, rated for 200A...


As a retail store there is no way this load will ever get over 180 amps. It is also the responsibility of the electrician who adds more load to calculate if there is enough amps available.

What happens when you use the 6 disconnect rule--- one could have a load of 100 amp on 6 breakers there is no breaker to trip.


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## Jmohl (Apr 26, 2011)

@ Dennis, I ain't EVEN trying to start a pissing match. From your posts I can tell you are one of the most code savvy guys out there. And yeah, a retail store is not gonna throw that much load on anything generally. Also true is the fact that any electrician adding to the sub SHOULD determine that there is adequate feeders to support any addition. In the real world though (as evidenced by a lot of the horror stories/pics in this forum) there are a lot of Hacks out there that don't. Five years from now, that retail space is a Chinese fast food joint with big azz steam tables, fryers, stoves, walk in, etc... and Quick Buck Elec. stuffs 200A on that sub..... Not your issue to be sure, but I lose sleep over stupid stuff I see all the time.


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## ohiosparky99 (Nov 12, 2009)

Probably not, but could it be your boss is referring to 310.15 (b) 6 and confused that this reference is for resi only?? just a thought


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## Salvatoreg02 (Feb 26, 2011)

4/0 alum is only acceptable for residential use only 310.15(b)(6)
200amps commercial requires 250alum.

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## nitro71 (Sep 17, 2009)

Salvatoreg02 said:


> 4/0 alum is only acceptable for residential use only 310.15(b)(6)
> 200amps commercial requires 250alum.
> 
> Sent from my iPhone using ET Forum


If the load is calculated above 175 amps but below 200 you have the option to size your conductors to the load and upsize your overcurrent protection to the next standard breaker size of 200 amps. Pretty sure you have to mark the panel also that the service is only good for what the wire is rated for.


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## Salvatoreg02 (Feb 26, 2011)

nitro71 said:


> If the load is calculated above 175 amps but below 200 you have the option to size your conductors to the load and upsize your overcurrent protection to the next standard breaker size of 200 amps. Pretty sure you have to mark the panel also that the service is only good for what the wire is rated for.


 Code reference please?

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## nitro71 (Sep 17, 2009)

Salvatoreg02 said:


> Code reference please?
> 
> Sent from my iPhone using ET Forum


Check out 240.4(B). :thumbsup:


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## Salvatoreg02 (Feb 26, 2011)

This is a new service. If your installing a new 200 amp service 250 alum is what you have to use. You have to provide documentation. Also based on what you said that 175 is your load they make a breaker that is 175amps. 
Plus you need to use a special breaker anyway. 240.4(b)(2)

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## nitro71 (Sep 17, 2009)

Salvatoreg02 said:


> This is a new service. If your installing a new 200 amp service 250 alum is what you have to use. You have to provide documentation. Also based on what you said that 175 is your load they make a breaker that is 175amps.
> Plus you need to use a special breaker anyway. 240.4(b)(2)
> 
> Sent from my iPhone using ET Forum


Over 175 and under 200. 

175 < Load < 200

Do you really think BBQ and Dennis are wrong?


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## Salvatoreg02 (Feb 26, 2011)

nitro71 said:


> Over 175 and under 200.
> 
> 175 < Load < 200
> 
> Do you really think BBQ and Dennis are wrong?


Yes, because then everyone will say the calculated load is 180 amps. 
You can't say 175 because the make a 175 amp breaker.

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## Salvatoreg02 (Feb 26, 2011)

nitro71 said:


> Over 175 and under 200.
> 
> 175 < Load < 200
> 
> Do you really think BBQ and Dennis are wrong?


They pose a hypothetical question. Any 200 amp service other then residential is 3/0 copper I've never used 4/0 alum for a 200a service other then se cable for residential use which is permitted. 
I understand you can but it won't fly with 99% of the AHJ unless it has a PE signature on it.

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## frenchelectrican (Mar 15, 2007)

Salvatoreg02 said:


> Yes, because then everyone will say the calculated load is 180 amps.
> You can't say 175 because the make a 175 amp breaker.
> 
> Sent from my iPhone using ET Forum


I don't really recalled to see a 175 amp breaker do you have something in the NEC did stated the standard size rating that do including the *175* amp verison ??


Merci,
Marc


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## Dennis Alwon (May 9, 2009)

frenchelectrican said:


> I don't really recalled to see a 175 amp breaker do you have something in the NEC did stated the standard size rating that do including the *175* amp verison ??
> 
> 
> Merci,
> Marc


Look at 240.6,,,, 175 amp breakers are a standard size but nor so available


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## BBQ (Nov 16, 2010)

Salvatoreg02 said:


> Code reference please?
> 
> Sent from my iPhone using ET Forum





nitro71 said:


> Check out 240.4(B). :thumbsup:


I posted that section in the start of this thread, you can lead an old dog to the words but you can't make them read. 



Salvatoreg02 said:


> This is a new service. If your installing a new 200 amp service 250 alum is what you have to use.


READ THE CODE SECTION :laughing:







> Plus you need to use a special breaker anyway. 240.4(b)(2)


What?


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## Dennis Alwon (May 9, 2009)

nitro71 said:


> If the load is calculated above 175 amps but below 200 you have the option to size your conductors to the load and upsize your overcurrent protection to the next standard breaker size of 200 amps. Pretty sure you have to mark the panel also that the service is only good for what the wire is rated for.


Nitro, be careful here--- if the calculated load is greater than 175 amps I agree but it must be 180 or less, not 200 or less to use 4/0 aluminum on a 200 amp breaker, unless this is residential service.

Thus if you had a calculated load of 190 amps then 4/0 aluminum is not compliant since it is rated 180 in T. 310.16.


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## Salvatoreg02 (Feb 26, 2011)

BBQ said:


> I posted that section in the start of this thread, you can lead an old dog to the words but you can't make them read.
> 
> READ THE CODE SECTION :laughing:
> 
> What?


240.4(b)(2)? 

Please elaborate in explaining to us how you would interpret this section only ??

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## Southeast Power (Jan 18, 2009)

crazymurph said:


> My boss is adding on to a retail space that he owns and I am installing the service. The service is 480 V., 3 phase, 200 amp. My boss wants to use 4/0 AL. in 3" pvc conduit. I called the inspector and he sais that we need to run 250kcmil. My boss is very insistant that we can use 4/0 XHHW. What am I missing?:help:


I think you need a new inspector in your town. I use 4/0 AL for 200 amps all of the time..:thumbsup:


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## Mulder (Sep 11, 2010)

jrannis said:


> I think you need a new inspector in your town. I use 4/0 AL for 200 amps all of the time..:thumbsup:


For resi thats fine. For any other service you have to show the load calcs to the inspector to justify your choice of 4/0.


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## RePhase277 (Feb 5, 2008)

Also, in many services, the transformer can't even supply enough current to meet the OCPD rating.


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## Salvatoreg02 (Feb 26, 2011)

InPhase277 said:


> Also, in many services, the transformer can't even supply enough current to meet the OCPD rating.


Good point!

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## nitro71 (Sep 17, 2009)

Pretty sure we're all on the same page here. Just arguing sematics.


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## BBQ (Nov 16, 2010)

InPhase277 said:


> Also, in many services, the transformer can't even supply enough current to meet the OCPD rating.


I am going to have to ask what service you have seen that to be the case?


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## RePhase277 (Feb 5, 2008)

BBQ said:


> I am going to have to ask what service you have seen that to be the case?


I see 200 A drops on #4 triplex 200+ ft. fed from a 40 kVA pole pig, also feeding 3 or 4 other services, around here all the time. I have done no math, but, while instantaneous fault current may be sizable, it doesn't seem like that system could supply 200 A for very long.


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## RIVETER (Sep 26, 2009)

crazymurph said:


> My boss is adding on to a retail space that he owns and I am installing the service. The service is 480 V., 3 phase, 200 amp. My boss wants to use 4/0 AL. in 3" pvc conduit. I called the inspector and he sais that we need to run 250kcmil. My boss is very insistant that we can use 4/0 XHHW. What am I missing?:help:


Sometimes, a person just has to listen to the boss...if the person making the decision IS the boss. It would be his call to tell you what to do. The AHJ would come in later.


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## Southeast Power (Jan 18, 2009)

Mulder said:


> For resi thats fine. For any other service you have to show the load calcs to the inspector to justify your choice of 4/0.


4/0 XHHW is good for 180 amps, I use the next size breaker up when its under 800 amps. XHHW-2 is good for 205 amps.

This info is from the manufacturers website:
http://www.cable.alcan.com/NR/rdonl...8E5E-2EC600FC5B27/0/STABILOYWiremansGuide.pdf

(page 30)

BTW, we always have to show load calculations..


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## electures (Oct 23, 2008)

BBQ said:


> In my opinion, unless your boss has provided load calculations to the inspector showing the load is less than 180 amps (4/0 ALs rating) the inspector can insist on conductors with an ampacity exceeding 200 amps.
> 
> On the other hand if the calculated load is under 180 amps, 4/0 AL is acceptable due to 240.4(B).


*240.4(B) Devices Rated 800 Amperes or Less. *The next higher
standard overcurrent device rating (above the ampacity of
the conductors being protected) shall be permitted to be
used, provided all of the following conditions are met:

(1) The conductors being protected are not part of a multioutlet
branch circuit supplying receptacles for cordand-
plug-connected portable loads.

(2) The *ampacity of the conductors* does not correspond
with the standard ampere rating of a fuse or a circuit
breaker without overload trip adjustments above its rating
(but that shall be permitted to have other trip or
rating adjustments).

(3) The next higher standard rating selected does not exceed
800 amperes. 

BBQ is correct. 240.4(B) states ampacity of conductors not calculated load.


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## EMeis1114 (Mar 5, 2011)

BBQ said:


> In my opinion, unless your boss has provided load calculations to the inspector showing the load is less than 180 amps (4/0 ALs rating) the inspector can insist on conductors with an ampacity exceeding 200 amps.
> 
> On the other hand if the calculated load is under 180 amps, 4/0 AL is acceptable due to 240.4(B).


Since Its 3 phase doesnt that mean you have to derate for more than three current carrying conductors?


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