Feeder size from outside disco

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madpenguin

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I know you guys are getting extremely sick and tired of this discussion but If you could see it your way to help me out on this, I'd be most appreciative.

It's the now age old discussion about 310.15(B)(6) vs. 310.16

Meter and siemens outdoor load center (being used as a diso with 100A main) is on the side of the house. From there #2 AL SER runs about 25 feet into the house to feed an old 90A Main push-matic.

Panel is getting ripped out (it's full) and replaced with probably a QO 100 Main Breaker Panel.

Area I'll be working in is on 08' code cycle. 338.10(B)(4)(A) ---> 334.80 tells me beyond a shadow of a doubt that the #2 SER needs to be replaced with either #2 CU or 1/0 AL.....

But here we go again with the new highlighted text in 310.15.... This "Main Feeder" between the disco and panel will be supplying all loads associated with the dwelling.... I can clearly see Type SE listed in Table 310.15(B)(6) and it says I'm good with the existing #2 AL....

Any help here would be greatly appreciated. I will say that there might be one slight "gotcha" and that is the disco outside still has two plates to break out that can supply one 240v load or 2 - 120v loads... Oh..... Also, there seems to also be 2-3 branch circuits running thru conduit from the indoor panel that feeds a detached garage.... ;-) That in itself is a violation if I'm not mistaken, but putting that aside, is a detached garage "associated with the dwelling"?

Any help? Thanks everyone a million.
 
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raider1

raider1

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IMHO, if you meet the requirements of a main power feeder, then you are permitted to use Table 310.15(B)(6) and use a #2 Aluminum SER cable with a 100 amp breaker.

Also, just because there are spaces for future breakers in the meter main doesn't mean you can't use 310.15(B)(6) if you have only installed a single feeder. If down the road someone chooses to install more breakers then the installation would be in violation.

Chris
 
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madpenguin

Member
Thanks Chris. I'm sure your probably not in the mood for a debate, but what say you to indoor Type SE needing to be rated at 60 Celsius thus seemingly contradicting 310.15?

I'm really starting to hate that new block of text in 08's 310.15.....
 
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raider1

raider1

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madpenguin said:
Thanks Chris. I'm sure your probably not in the mood for a debate, but what say you to indoor Type SE needing to be rated at 60 Celsius thus seemingly contradicting 310.15?

I'm really starting to hate that new block of text in 08's 310.15.....
Click to expand...

I personally don't see a contradiction. 334.80 states The ampacity of Types....... shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60 degree C conductor temperature rating.

310.15(B) says we use the tables as modified by (B)(1) through (B)(6). 310.15(B)(6) modifys the general rule to use 310.16 and permits us to use Table 310.15(B)(6) under the specified conditions.

Chris
 
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madpenguin

Member
raider1 said:
I personally don't see a contradiction. 334.80 states The ampacity of Types....... shall be determined in accordance with 310.15.
Click to expand...

Yes, Types NM, NMC and NMS....... I'm not seeing SEU or SER in there...

The ampacity shall be in accordance with the 60 degree C conductor temperature rating.
Click to expand...

After reading 338.10(B)(4)(A), one must assume that indoor type SE has to comply with the direct above quote which can only lead you to Table 310.16

310.15(B) says we use the tables as modified by (B)(1) through (B)(6). 310.15(B)(6) modifys the general rule to use 310.16 and permits us to use Table 310.15(B)(6) under the specified conditions.
Click to expand...

Therefore, One shouldn't even be turning to 310.15 (B)(1) thru (B)(6).... I'm also not seeing anywhere where 310.15 permits/"modifies" 310.16 usage but maybe I'll go back and read it again.

Ughhh man... I just don't know. I'm likely to just leave the #2 and say the hell with it. I really would like to know the specific intent of the code tho, but I'm just not seeing your train of thought.
 
augie47

augie47

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//dragging up my soapbox//
I've been deep in this debate since I first opened '08. There are definitely two schools of though and I won't rehash them here (you can search 338.10 and find most).
In my current inspection position I am called upon to work areas of 5 different inspectors (in TN). In two of those jurisdictions, following their lead, you would need a 1/0 AL, in three areas, you could use #2.
That said, some who were allowing the #2 are rethinking now that they have read the draft of 2011.
I think it's say to say you are in an area of the Code where the AHJ will decide.
 
raider1

raider1

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madpenguin said:
Yes, Types NM, NMC and NMS....... I'm not seeing SEU or SER in there...
Click to expand...

That is because 334.80 is located in the NM cable Article.

After reading 338.10(B)(4)(A), one must assume that indoor type SE has to comply with the direct above quote which can only lead you to Table 310.16
Click to expand...

Why must you assume that? If you read section 334.80 it states the ampacity shall be determined in accordance with 310.15. Again 310.15(B) states that you uses Tables 310.16 through 310.19 and ampacity Tables 310.20 and 310.21 as modified by (B)(1) through (B)(6). So Table 310.15(B)(6) modifies the general rule to use the other tables and permits you to use Table 310.15(B)(6) if you meet the requirements in that section.

Therefore, One shouldn't even be turning to 310.15 (B)(1) thru (B)(6).... I'm also not seeing anywhere where 310.15 permits/"modifies" 310.16 usage but maybe I'll go back and read it again.
Click to expand...

Again I disagree, 310.15(B)(6) modifies the general requirement to use Table 310.16.

Ughhh man... I just don't know. I'm likely to just leave the #2 and say the hell with it. I really would like to know the specific intent of the code tho, but I'm just not seeing your train of thought.
Click to expand...

I would recommend reading 310.15(B).

Chris
 
Dennis Alwon

Dennis Alwon

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I agree with Chris. First off does this sub panel carry the entire load of the panel? If yes, I am with Chris. Gus sees it differently, if my memory serves me.;)

If this panel does not meet the criterion of serving all the loads of the house then I would put an 80 amp breaker on it as long as that will be enough ampacity to serve the load. As long as the 80 amp breaker is ahead of the panel then the 100 amp breaker in the panel really doesn't matter.

So I guess we need to know what is the calculated load of the panel?
 
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madpenguin

Member
Oh boy, oh boy, oh boy.... ;)


raider1 said:
Why must you assume that? If you read section 334.80 it states the ampacity shall be determined in accordance with 310.15.
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Yes. It does. With types NM, NMC and NMS....

Again 310.15(B) states that you uses Tables 310.16 through 310.19 and ampacity Tables 310.20 and 310.21 as modified by (B)(1) through (B)(6).
Click to expand...

Yep. It does. Split that into 2 sections which is how they have lettered it.

310.15(B) Tables. Ampacities for conductors rated 0 to 2000 volts shall be as specified in the allowable apacity table 310.16 through table 310.19,
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STOP. Ok. My SER is most certainly within 0 to 2000 volts. I'm good for 310.16 thru 310.19 as of this point.

,and ampacity table 310.20 and table 310.21 as modified by (B)(1) through (B)(6)
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O.k.... Sorry but my indoor SER cable certainly doesn't have a messenger wire or is free air with wind velocity involved.....

That leaves me with 310.16 thru 310.19.... My indoor SER cable can only comply with 310.16. Period. I don't even need to read past 310.15(B), along with 338.10(B)(4)(A) telling me I have to comply with 334.80's 60 Celsius rule, I'm done..... Table 310.16 or nothing......

So Table 310.15(B)(6) modifies the general rule to use the other tables and permits you to use Table 310.15(B)(6) if you meet the requirements in that section.
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I still don't see how Article 310.15(B)(6) modifies anything. It flat out states a direct requirement in order to use Table 310.15(B)(6).

Again I disagree, 310.15(B)(6) modifies the general requirement to use Table 310.16.
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You say modify, I say contradict. This whole thing makes no sense to me......

Now please don't think I'm trying to argue and push buttons. I'm actually enjoying this discussion and I just can't see for the life of me how Table 310.15(B)(6) can be used here.

If I had a meter on one side of the house but I decided to wrap 100 feet of SEU along the side of the house to enter an outside disconnect, then most certainly, I would size that SEU according to table 310.15(B)(6). But as soon as I took my SER from the disco to the indoor panel it would be sized according to Table 310.16....
 
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Dennis Alwon

Dennis Alwon

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Chapel Hill, NC
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Retired Electrical Contractor
madpenguin said:
But as soon as I took my SER from the disco to the panel it would be sized according to Table 310.16....
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That is your opinion and a very valid one. Table 310.15(B)(6) may not modify but it allows SE cable to be use-- it's listed in the heading-- as long as the requirements of 310.15(B)(6) are met. Now does Table 310.15(B)(6) say only if 338.10(B)(4)(a) does not come into play. No... so take your pick. Personally I agree with your thinking but I don't think the NEC reads that way. I would ask the AHJ since he/she will have the final say.
 
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madpenguin

Member
Dennis Alwon said:
Table 310.15(B)(6) may not modify but it allows SE cable to be use-- it's listed in the heading-- as long as the requirements of 310.15(B)(6) are met.
Click to expand...

And thats why it's in direct conflict with 338.10(B)(4)(a).... Not unless you have a strictly outdoor loadcenter supplying all branch circuits to the dwelling..... Fine. No argument there. All Type SE is outdoors now.

Ah..... To hell with it. You know, the code panel really needs to think these things out a tad more before they publish. I haven't read the 11' draft so all I know is that I have a headache. ;)

Thanks Raider (and others) for the debate. All for the sake of knowledge and no harm intended...
 
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madpenguin

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Thanks for the link. I've actually thought that same thing since 08' came out. It really doesn't make any sense and is Bass Ackwards.
 
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