Service entrance condutors

[ryan_618]

I would like some thoughts on this. In an underground installation (residential) It is common in my area to use a can with a meter and space for about 6-10 breakers. The POCO comes in on the service lateral and hooks into the line side of the meter. Off of the load side of the meter are two bus bars that connect to the panelboard, creating the two phases. With this information, how do you size the GEC? Are there no service entrance conductors and therefore note 2 to table 250.66 applies? Or are the bus bars from the load side of the meter to the phases in the panelboard considered service entrance conductors and sized at the maximum rating of the panel?

If this question makes no sense please let me know and I will edit it as possible. Thanks in advance.

 

[Guest]

Re: Service entrance condutors

I would size it on the maximum rating of the panel.

 

[iwire]

Re: Service entrance condutors

Originally posted by awwt:
I would size it on the maximum rating of the panel.

Wayne the question is not what you or I would do, but what the NEC requires.

 

[Guest]

Re: Service entrance condutors

Right, and if the NEC says I can size it smaller, I choose to size it to the maximum panel rating.

../Wayne C.

 

[roger]

Re: Service entrance condutors

Ryan, first of all there are no "phases" (I'll explain when neccassary) then the residential GEC would probably be #6 or #4 depending on the type of GE.

Roger

 

[don_resqcapt19]

Re: Service entrance condutors

In my opinion there are no service entrance conductors and note 2 to Table 250.66 applies. This would mean that you would use the load calculations, to size the service entrance conductors that would be required for the load and then use Table 250.66. That being said, the easiest way would be just to use the panel rating to size the GEC.
Don

 

[ryan_618]

Re: Service entrance condutors

Roger I know what you are saying. I used the terminoligy for ease of explanation. Thanks though.

Don, I am thinking you are right. I believe that given the choice of increasing the GEC or performing article 215.5, most residential installers will choose increasing the GEC. ( I mean no disrespect to anyone by that).

Now, lets talk definitions:

1)Service-Entrance Conductors, Underground System. The service conductors between the terminals of the service equipment and the point of connection to the service lateral.
FPN: Where service equipment is located outside the building walls, there may be no service-entrance conductors, or they may be entirely outside the building.

Keeping it simple...what is a conductor?

2)Conductor.
Bare. A conductor having no covering or electrical insulation whatsoever.
Covered. A conductor encased within material of composition or thickness that is not recognized by this Code as electrical insulation.
Insulated. A conductor encased within material of composition and thickness that is recognized by this Code as electrical insulation.

It appears that a conductor is not defined in the code. Heres what the dictionary has to say:

3)Conductor: A thing that conducts heat or electricity.

That being said...are bus bars conductors (in the NEC context)? If so, does the above installation have service entrance conductors?

BTW: I am not trying to be argumentitive, nor am I trying to stretch the code, I'm just trying to learn a bit.

Thanks for your replies.

 

[iwire]

Re: Service entrance condutors

Ryan this "no service conductor" issue is confusing to me.

In your area who provides the conductors from the service disconnect back to the utility?

In this area that would be us not the POCO.

For a dwelling unit service lateral this would be underground and up a pole with slack to reach the spot they are connecting or underground to a pad mount transformer that may feed one or more dwellings.

We would provide the raceway and cable all under the NEC sizing guidelines so using 250.66 is easy.

 

[ryan_618]

Re: Service entrance condutors

Originally posted by iwire:
In your area who provides the conductors from the service disconnect back to the utility?

Bob, that would be the POCO here.
BTW this is confusing to me too, thats why I posted it !

 

[bob]

Re: Service entrance condutors

Ryan
You did not say you had a main breaker. If not how are you getting by 230.71 which requires a max of 6?

[ September 24, 2003, 05:08 PM: Message edited by: bob ]

 

[ryan_618]

Re: Service entrance condutors

Originally posted by bob:
Ryan
You did not say you had a main breaker. If not how are you getting by 230.7 which requires a max of 6?

It doesn't have a main breaker. If it did this question would be easy. I don't allow more than six, despite the fact that the panel can accomodate more than six. I can not red-tag a violation that isn't there yet.
Thanks for your question Bob.

 

[don_resqcapt19]

Re: Service entrance condutors

The supply to the meter combo is a serivce lateral, not service entrance conductors. This does not change even if the contractor provides and installs these conductors. Table 250.66 is based on service entrance conductors. This type of installation is one of the reasons for Note 2 to Table 250.66.
Don

 

[iwire]

Re: Service entrance condutors

OK Don another clear as mud issue to me.

Service Lateral. The underground service conductors between the street main, including any risers at a pole or other structure or from transformers, and the first point of connection to the service-entrance conductors in a terminal box or meter or other enclosure, inside or outside the building wall. Where there is no terminal box, meter, or other enclosure, the point of connection is considered to be the point of entrance of the service conductors into the building.

Taking that definition alone it seems clear but now when I look at this definition

Service Conductors. The conductors from the service point to the service disconnecting means.

And this one it is not so clear,

Service Point. The point of connection between the facilities of the serving utility and the premises wiring.

to me it looks like the conductors are both service laterals and service conductors.

Can you help me out here?

Remembering we provide the meter enclosure too, so where do the utility facilities end?

[ September 24, 2003, 05:35 AM: Message edited by: iwire ]

 

[pierre]

Re: Service entrance condutors

Bob
one of the issues that we all are learning to deal with is the enormity (large scale size) of our industry based on the size and diversity of the work performed in this country.
That being said some things are done different in different parts of the country.
The service laterals that Ryan are talking about may be one of those instances.
250.66 note 2, explains the procedure to size the GEC when there are 'no service entrance conductors'.

Ryan's case has no service entrance conductors, so he will follow note 2. He performs a load calculation for the load of the building and than has the number he needs to figure his GEC.

BTW - Bus bars are considered conductors.

If you are unsure as to performing the load calculation, Example D1(a) and D2(b) in the annex at the back of the NEC are good to follow. Don't forget to read 220.3.
Don's first post would be the easiest/fastest way to figure the correct size.
Good luck

Pierre

 

[don_resqcapt19]

Re: Service entrance condutors

Bob,
I agree that the code has a problem with the definition of service point. In my opinion, it should be redefined to say that the service point is the point at which the ownership of the energy passes from the utility to the customer. That would make the service point the metering equipment. Under the current code, the service laterals and metering equipment is still under the "exclusive control" of the utility no matter who provides and installs those items. In this case I would say that the service point is the load side of the meter.
Don

 

[eprice]

Re: Service entrance condutors

It seems to me, as Ryan has suggested, that the bus bars from the meter into the breaker panel may technically be the service entrance conductors in this case. I would guess (and it's only a guess) that using thier cross sectional area or the panel rating to size the GEC would result in about the same size GEC. I would think that the size of those bus bars would be a factor in ariving at the panel rating?

Another question: In a situation where there are clearly identifiable service entrance conductors, if service entrance conductors are installed that are larger than required for the load being served, would everyone agree that the size of the GEC should still be based on the size of those oversized service entrance conductors and not not the load being served?

 

[don_resqcapt19]

Re: Service entrance condutors

eprice,
The GEC is always based on the service entrance conductor size if there are service entrance conductors. The only time the GEC is permited to be based on the calculated load is the case where there are no service entrance conductors.
Don

 

[iwire]

Re: Service entrance condutors

Pierre Thanks, Ryan and I have been discussing this through PMs before this post we are both aware of Note 2 and I also suggested at ECN that it would be easer to just go by the panel size then to do the calculations.

Don, I do appreciate your input and I am not trying to be a pain in the rear.

I think what we have is just what Pierre has said different ways for different areas.

In the case of the service lats here the POCO does not inspect or care about them the NEC inspector does, how can we say that the conductors that the customer pays for and maintains are under the control of the utility?

Another typical installation we do the POCO stops at a pad mount transformer we provide from there we go underground inside the building into switch gear, first stop the service disconnect then the CT metering compartment.

In this case we/the customer maintain control over the disconnect (fused switch or breaker) the section with the CTs gets POCO locks and seals.

We still treat the conductors from the transformer to the main disco as service entrance conductors.

It is interesting to see how we all do the same thing differently.

Ryan sorry for hijacking your question.

Bob

 

[don_resqcapt19]

Re: Service entrance condutors

Bob,
In my opinion, everything on the line side of the "cash register" and the "cash register" itself is under the exclusive control of the utility. The customer is not permitted by the rate or tariff agreement to access that part of the system. The fact that the customer installed and paid for this equipment does not change this. Maybe Charlie would have some input on this issue. This is all part of the problem with the definition of "service point".
don

 

[Guest]

Re: Service entrance condutors

Looking from the outside it would seem that anything that is unmetered should be sealed to avoid theft of power. It would also make sense to lock seal & lock anything ahead of the service disconnect to avoid injury to unqualified personnel (and to minimize the liablity exposure of the POCO) .

When I pay extra to underground vs. a free overhead drop I don't get to own, control, or maintain the underground.

I know iWire's situation is real, but it does not make sense from a distance.