Hypothetical 400a service

[Dennis Alwon]

Mike I am saying that the 2011 NEC allows the busbar as a connection between panel for the tap conductor. Some believe it was not allowed and a split bolt must be used.

 

[jxofaltrds]

Mike I am saying that the 2011 NEC allows the busbar as a connection between panel for the tap conductor. Some believe it was not allowed and a split bolt must be used.

I do not have the 2011 so I can not debate this.

So I understand. Two 'main' panels side by side. Not connected physically.

We bond the two 'main' panels together at the grounded conductor?

 

[Dennis Alwon]

I do not have the 2011 so I can not debate this.

I know how much you like to debate , that is why I posted the article in post #19.

 

[Dennis Alwon]

I do not have the 2011 so I can not debate this.

So I understand. Two 'main' panels side by side. Not connected physically.

We bond the two 'main' panels together at the grounded conductor?

I thought we were talking the GEC not grounded conductors. The picture had a 1/0 to the water pipe and a jumper between panels with a #4. This was not clear as an acceptable means until 2011 when it allows the busbar as a tap.

 

[jxofaltrds]

I thought we were talking the GEC not grounded conductors. The picture had a 1/0 to the water pipe and a jumper between panels with a #4. This was not clear as an acceptable means until 2011 when it allows the busbar as a tap.

Yes. We are talking about the same picture. The #4 is attached to the grounded conductors. I say no.

Any problem with the left panel line/load nuetrals being on the wrong side?

 

[Dennis Alwon]

Yes. We are talking about the same picture. The #4 is attached to the grounded conductors. I say no.

Any problem with the left panel line/load nuetrals being on the wrong side?

If the two bars are joined together than what difference does it make if it is attached to the side of the grounded conductor. It is all tied together.

 

[busman]

Yes, since the service conductors do not carry the entire load of the service thenT.310.15(B)(6) does not apply. Where in the table does it allow for 2 sets of 2/0? It doesn't because you cannot control the diversity that is in dwellings when the load is split. 3/0 is needed.

Dennis,

I respectfully disagree. The language of 310.15(b)(6) specifically allows multiple feeders and defines them as the conductors from the main disconnect to the lighting/appliance branch circuit panelboards. I believe that the code allows that installation as long as the combined entrance cables and feeders carry the entire load.

Certainly around here, it is gospel on 400A services to use a 320/400 meter can with two 4/0 aluminum SE cables entering two 200A MCB panels. You're implying this violates code? If so, there's a lot of code violations in Northern Virginia.

Mark

 

[augie47]

busman...
this has been a highly debated subject since the onset of 310.15(B)(6)
As I recall, in the '08 Code, to try and soften the debate, the CMP used the singular word "feeder" to designate ONE supply. If the whole house load was fed by more than one service/feeder the 310.15(B)6) did not apply. That was a change from the '-5 Code and I'm pretty sure it went back to plural in '11. Mr Holt submitted changes to that effect.
To review the process one has to go back and look at the ROPs and ROCs.

I am of the opinion that if one is under '08 with two feeders, 310.16(B)(6) does not apply. That said, it is one of the most overlooked sections.

 

[busman]

busman...
this has been a highly debated subject since the onset of 310.15(B)(6)
As I recall, in the '08 Code, to try and soften the debate, the CMP used the singular word "feeder" to designate ONE supply. If the whole house load was fed by more than one service/feeder the 310.15(B)6) did not apply. That was a change from the '-5 Code and I'm pretty sure it went back to plural in '11. Mr Holt submitted changes to that effect.
To review the process one has to go back and look at the ROPs and ROCs.

I am of the opinion that if one is under '08 with two feeders, 310.16(B)(6) does not apply. That said, it is one of the most overlooked sections.

Thanks for the info. We are still on 2005. Wondering when the USBC will be updated for the 2008. I try not to look at the new book until it's adopted. Just confuses me.

Thanks again,

Mark

 

[Dennis Alwon]

Thanks Gus-- for helping me out.

It has always been my interpretation, even before the NEC 2008 that the install needed 3/0 copper. For one , show me in T. 310.15(B)(6) what it states for a 400 amp service. I will save you the problem-- it states 400 kcm copper not 2- 2/0 copper conductors. IMO, it never allowed for 2 service entrance runs. The idea behind this is that residential loads are diversified however when you split the load into 2 sets of service conductors that diversity is gone.

 

[busman]

Thanks Gus-- for helping me out.

It has always been my interpretation, even before the NEC 2008 that the install needed 3/0 copper. For one , show me in T. 310.15(B)(6) what it states for a 400 amp service. I will save you the problem-- it states 400 kcm copper not 2- 2/0 copper conductors. IMO, it never allowed for 2 service entrance runs. The idea behind this is that residential loads are diversified however when you split the load into 2 sets of service conductors that diversity is gone.

I still have to respectfully disagree, unless you can explain to me why it was plural - feeder(s) - in the 2005 code.

Mark

 

[Dennis Alwon]

I still have to respectfully disagree, unless you can explain to me why it was plural - feeder(s) - in the 2005 code.

Mark

We can argue this all day as we have in the past. Let me try again..
First off these are not feeders....Yes?
Secondly is the Table will not allow it or has no provision for this install.

 

[busman]

We can argue this all day as we have in the past. Let me try again..
First off these are not feeders....Yes?
Secondly is the Table will not allow it or has no provision for this install.

OK, so I didn't type the whole thing. It says:

"... single-phase service-entrance conductors, service lateral conductors and feeder conductors..."

The one in question in the OP was the feeder to the other side of the house from the 200A disconnect as described in:

"For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch circuit panelboard(s)."

How is this not applicable to more than one set?? If they don't mean more than one set, what DO they mean by making it plural??

Mark

 

[Dennis Alwon]

Read above that where it says ...feeder conductors that serve as the main power feeder to each dwelling unit and installed in.......

IMO, they are talking about the feeders in a multifamily dwelling. In other wrds the feeder to each unit.

It also states it must be the main power feeder. How can you have more than one main power feeder-- it is singular. I also believe that 2008 just clarified what was stated in 2005. Not a change per se but a clarification.

 

[augie47]

Busman,
We can take this to post #100 (and it has probably been there previously) and in the end it will depend on the AHJ in the area in question.
It has been long debated and changed each Code cycle.

The wording you quoted seems to be from the '05 Code. In '08, the (s) to feeder* was dropped and the Handbook gave the following explanation:

Section 310.15(B)(6) permits the main feeder to a dwelling unit to be sized according to the conductor sizes in Table 310.15(B)(6). For the 2008 Code, the panel clarified that this permission to use this table applies only to conductors carrying 100 percent of the dwelling unit's diversified load.

Admitting the Handbook is not "Code", but the explanation reflects comments made in the ROPs and ROCs supporting the change.
Apparently, prior to '08 is was debatable as to using 310.15(B)(6) on multiple feeders. '08 tried to clarify that. In your mind it may still be debatable, and that may be true for the AHJ in the OPs area.
I think I speak for Dennis and I know for myself, in enforcing the '08
Code we see it as a singular feeder/service carrying 100% of the diversified load.
You are, of course, welcome to see it differently.

I have not researched '11, but I'd told it went back to feeder(S).

 

[Dennis Alwon]

I have not researched '11, but I'd told it went back to feeder(S).

Someone told you wrong. The only thing that changed in 2011 is the article & Table number. They are now 310.15(B)(7).

I think busman was talking about the 2005.

 

[busman]

Read above that where it says ...feeder conductors that serve as the main power feeder to each dwelling unit and installed in.......

IMO, they are talking about the feeders in a multifamily dwelling. In other wrds the feeder to each unit.

It also states it must be the main power feeder. How can you have more than one main power feeder-- it is singular. I also believe that 2008 just clarified what was stated in 2005. Not a change per se but a clarification.

I was certainly talking about the 2005 code. I'm glad it's been fixed in 2008. With respect to singular or plural, the quote was:

"For application of this section, the main power feeder shall be the feeder(s)"

Which says that the "Main Power Feeder" can be more than one feeder. You could be right that the intent was that it only be plural for multi-dwelling units, but it doesn't say that. I'm trying to stick to what it says, and not what it implies. If it were clear as written, I don't know why they would have changed it for 2008.

Respectfully,

Mark

Mark

 

[busman]

By the way, for what it's worth, from a technical point of view, I agree that you shouldn't be able to use the table to reduce sizing of the conductors since that's based on the load diversity in the load calculation.

In the extreme example, there could be a "400A service" that had all the load in one loadcenter on a 200A breaker and the other loadcenter left empty for "future expansion". The 2008 change is a good one in my opinion.

Mark