allenwayne
Senior Member
Re: 250.66
230.D E,but 250.66 say to size to largest,incoming feeder.How do we comply with both
230.D E,but 250.66 say to size to largest,incoming feeder.How do we comply with both
250.66
- Thread starter paul renshaw
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: 250.66
This would not be true if you had an overhead service drop. You need to look at the definitions in Article 100 referring to Service Entrance Conductors. In an overhead system the service entrance conductors would begin at the point where they are attached to the service drop.
paul renshaw
Senior Member
- Location
- Cordova, Maryland
Re: 250.66
I did look at the definitions,which is why in my opinion the size of the conductors coming to the meter are irrelevant to the calculation. The service lateral is underground, sorry if I implied otherwise.
[ December 24, 2005, 03:40 PM: Message edited by: paul renshaw ]
I did look at the definitions,which is why in my opinion the size of the conductors coming to the meter are irrelevant to the calculation. The service lateral is underground, sorry if I implied otherwise.
[ December 24, 2005, 03:40 PM: Message edited by: paul renshaw ]
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Re: 250.66
I would say that the tap to each panel be sized for that panel's feeders, 3/0, and each of those taps be connected to a bonding conductor sized to the equivalent of two 3/0's.
I would say that the tap to each panel be sized for that panel's feeders, 3/0, and each of those taps be connected to a bonding conductor sized to the equivalent of two 3/0's.
Re: 250.66
I thought that service enterance conductors meant the wires from where the utility makes its connection to the customer provided wires. It doesnt matter if they are on the line, or load side of the meter.
The utility engineers thier wires on a case by case basis. We size our wires based on the NEC.
I thought that service enterance conductors meant the wires from where the utility makes its connection to the customer provided wires. It doesnt matter if they are on the line, or load side of the meter.
The utility engineers thier wires on a case by case basis. We size our wires based on the NEC.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: 250.66
JB you are correct service entrance conductors start at the connection from the drop. They continue till you hit the first service disconnect(s) This would be on an overhead service. The meter is only a wide place in the SEC's.
Where many confuse this is in underground laterals in which stop at the first connection point after they leave the ground, in most cases this would be in the meter. But a troff could be installed under the meter then this would be that connection point. From this connection point to the first service disconnect is again SEC's.
Remember there are some installations that don't even have any SEC's. So then all you do is size the EGC from 250.66 to the size of the ungrounded SEC conductor that would have been required if you were to install it.
See note 2 to table 250.66
JB you are correct service entrance conductors start at the connection from the drop. They continue till you hit the first service disconnect(s) This would be on an overhead service. The meter is only a wide place in the SEC's.
Where many confuse this is in underground laterals in which stop at the first connection point after they leave the ground, in most cases this would be in the meter. But a troff could be installed under the meter then this would be that connection point. From this connection point to the first service disconnect is again SEC's.
Remember there are some installations that don't even have any SEC's. So then all you do is size the EGC from 250.66 to the size of the ungrounded SEC conductor that would have been required if you were to install it.
See note 2 to table 250.66
paul renshaw
Senior Member
- Location
- Cordova, Maryland
Re: 250.66
Larry, that is kind of what I think too, but this building has the GEC that runs to the electrodes sized per 1 3/0. This is an existing installation I came upon and I was just questioning if it was done properly.
jb, as infinity pointed out, sometimes it depends on the installation, overhead or underground. Look at the definition for both, and the definition of service point.
[ December 24, 2005, 03:35 PM: Message edited by: paul renshaw ]
Larry, that is kind of what I think too, but this building has the GEC that runs to the electrodes sized per 1 3/0. This is an existing installation I came upon and I was just questioning if it was done properly.
jb, as infinity pointed out, sometimes it depends on the installation, overhead or underground. Look at the definition for both, and the definition of service point.
[ December 24, 2005, 03:35 PM: Message edited by: paul renshaw ]
Re: 250.66
My reading of 250.66 says to add the area of the two 3/0's together to determine your service entrance conductor size. So you'll need a 1/0 copper from one of the panels or someplace along the service neutral to your structural steel or water pipe. You may run two smaller #4 copper taps (one from each panel) to this larger GEC if you want.
My reading of 250.66 says to add the area of the two 3/0's together to determine your service entrance conductor size. So you'll need a 1/0 copper from one of the panels or someplace along the service neutral to your structural steel or water pipe. You may run two smaller #4 copper taps (one from each panel) to this larger GEC if you want.
pierre
Senior Member
- Location
- Westchester County, New York
Re: 250.66
As Wayne has stated, look at note 2.
If there are no service entrance conductors, use the equivalent size.
As Wayne has stated, look at note 2.
If there are no service entrance conductors, use the equivalent size.
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: 250.66
Paul you've brought up an interesting question. After reading notes 1 & 2 I'm still not sure that you would need to use the equivalent of 2 sets of #3/0 in the scenerio that you've proposed. Either way I look at it the exceptions are poorly written and don't seem to fit your installation.
I'd guess that the safest way would be to add them together and use their equivalent size but I don't see where it's clearly required to do so.
Trevor
Paul you've brought up an interesting question. After reading notes 1 & 2 I'm still not sure that you would need to use the equivalent of 2 sets of #3/0 in the scenerio that you've proposed. Either way I look at it the exceptions are poorly written and don't seem to fit your installation.
It seems that note #1 would apply to parallel service entrance conductors in an overhead service so this would not apply to your setup.
Note #2 would apply if no service entrance conductors were present at all. This doesn't seem to apply to your installation either since you indeed have service entrance conductors on the load side of the meter.
I'd guess that the safest way would be to add them together and use their equivalent size but I don't see where it's clearly required to do so.
Trevor
paul renshaw
Senior Member
- Location
- Cordova, Maryland
Re: 250.66
Merry X-mas all!!! I wasn't sure either because 230.40 ex 2 says service drop or lateral, which implies overhead or underground.(I am looking in 02 NEC, 05 is at work)
Merry X-mas all!!! I wasn't sure either because 230.40 ex 2 says service drop or lateral, which implies overhead or underground.(I am looking in 02 NEC, 05 is at work)
Re: 250.66
Why do you say that? The service entrance conductors go all the way to each disconnect whether from a drop or a lateral, they don't stop at the meter. And 230.40 Exception 2 says "service drop or lateral". I think that note 1 is the answer to the poster's question.
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: 250.66
Not if you read the definitions of service entrance conductors. Overhead and underground service entrance conductors begin at a different point by the definitions in Article 100.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: 250.66
Trevor
Note 1 does apply as he has the same setup that 230.40 exception 2 allows.
Multiple conductors are not parallel conductor as the exception 2 to 230.40 is where one set of serive entrance conductors are split to run to two seperate inclosures. Connected together on the feeding end but seperated on the load end. This is exactly what paul has.
This is not parallel conductors.
Trevor
Note 1 does apply as he has the same setup that 230.40 exception 2 allows.
Multiple conductors are not parallel conductor as the exception 2 to 230.40 is where one set of serive entrance conductors are split to run to two seperate inclosures. Connected together on the feeding end but seperated on the load end. This is exactly what paul has.
This is not parallel conductors.
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: 250.66
Note #2 says that "where there are no service entrance conductors", but by the definition the conductors on the load side of the meter are service entrance conductors so note #2 would not apply either. So Paul's original question about sizing the GEC, when applied to his installation, is not clearly defined due to wording of both notes #1 and #2.
So since we have a set of #3/0 service entrance conductors from the load side of the meter to each panel do we size the GEC according to only 1 set of #3/0?
This is the problem with 250.66 note #1. The underground conductors that are feeding the meter are not service entrance conductors. By definition in Article 100 they are a service lateral so note #1 does not apply to his installation.
Note #2 says that "where there are no service entrance conductors", but by the definition the conductors on the load side of the meter are service entrance conductors so note #2 would not apply either. So Paul's original question about sizing the GEC, when applied to his installation, is not clearly defined due to wording of both notes #1 and #2.
So since we have a set of #3/0 service entrance conductors from the load side of the meter to each panel do we size the GEC according to only 1 set of #3/0?
Re: 250.66
I don't think you're reading far enough into the definition of service entrance conductors. Yes, overhead and underground start at different points. But if you have a meter, wires from the meter to the disconnects are service entrance conductors too. There are two sets of them in this installation.
I think the only way you can have no service entrance conductors is with an all in one meter-main service fed from underground conductors.
Service-Entrance Conductors, Underground System.
The service conductors between the terminals of the service equipment and the point of connection to the service lateral.
Service Conductors. The conductors from the service point to the service disconnecting means.
Service Equipment. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.
I don't think you're reading far enough into the definition of service entrance conductors. Yes, overhead and underground start at different points. But if you have a meter, wires from the meter to the disconnects are service entrance conductors too. There are two sets of them in this installation.
I think the only way you can have no service entrance conductors is with an all in one meter-main service fed from underground conductors.
Service-Entrance Conductors, Underground System.
The service conductors between the terminals of the service equipment and the point of connection to the service lateral.
Service Conductors. The conductors from the service point to the service disconnecting means.
Service Equipment. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.
Re: 250.66
230.1 scope. when looking at art. 230, service-entrance conductors are thoes conductors between the terminal box, meter, or other encloseure and the service equipment. as I see this case it is one meter feeding 2 diconects as outlined in 230.40 exception 2. therfore the sum of the largest of each set per 250.66 exmp 1. 3/0 167,600 cm x 2 = 335,200cm ie 1/0 ground. My math may be wrong not the best at this.
[ December 26, 2005, 09:30 PM: Message edited by: wyatt ]
230.1 scope. when looking at art. 230, service-entrance conductors are thoes conductors between the terminal box, meter, or other encloseure and the service equipment. as I see this case it is one meter feeding 2 diconects as outlined in 230.40 exception 2. therfore the sum of the largest of each set per 250.66 exmp 1. 3/0 167,600 cm x 2 = 335,200cm ie 1/0 ground. My math may be wrong not the best at this.
[ December 26, 2005, 09:30 PM: Message edited by: wyatt ]
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: 250.66
Trevor
Note the two definition's below
In each the service entrance conductors will be the two 3/0 conductors that run from the meter to each service disconnect as allowed by exception 2 to 230.40, these might not run inside the building at all, as the FPN to the definition below states.
You are correct that the conductors that run up to the meter are in fact the service laterals and do stop at the connection to the meter.
As I had said in a previous post, if a trough was to be located below the meter and the "first point of connection was in this trough then the service entrance conductors would start at this point but this has no bearing on what the OP was asking.
He has two sets of 3/0 ungrounded conductors that leave the meter and land each set in a service disconnect and by note 1 these are the conductors that he is to use in determining the size of the grounding electrode conductor from.
Now 250.66 also states that if the grounding electrode conductor is the sole conductor to a rod type electrode then it does not have to be larger than a #6.
But a GEC to building steel or a water pipe then it does have to be determined by the largest sum of the areas of the corresponding conductors of each set.
It is nothing more then a wide space in the service entrance conductors (Over head service) or a connection point for the service laterals (Underground service)
Charlie E has pointed this out many times here in this forum.
[ December 27, 2005, 01:36 AM: Message edited by: hurk27 ]
Trevor
Note the two definition's below
In each the service entrance conductors will be the two 3/0 conductors that run from the meter to each service disconnect as allowed by exception 2 to 230.40, these might not run inside the building at all, as the FPN to the definition below states.
You are correct that the conductors that run up to the meter are in fact the service laterals and do stop at the connection to the meter.
As I had said in a previous post, if a trough was to be located below the meter and the "first point of connection was in this trough then the service entrance conductors would start at this point but this has no bearing on what the OP was asking.
He has two sets of 3/0 ungrounded conductors that leave the meter and land each set in a service disconnect and by note 1 these are the conductors that he is to use in determining the size of the grounding electrode conductor from.
Now 250.66 also states that if the grounding electrode conductor is the sole conductor to a rod type electrode then it does not have to be larger than a #6.
But a GEC to building steel or a water pipe then it does have to be determined by the largest sum of the areas of the corresponding conductors of each set.
Edited to add that again: A meter is not service equipment. (230.66)
It is nothing more then a wide space in the service entrance conductors (Over head service) or a connection point for the service laterals (Underground service)
Charlie E has pointed this out many times here in this forum.
[ December 27, 2005, 01:36 AM: Message edited by: hurk27 ]
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: 250.66
OK, so now I think that I've got it. I was getting hung up on the wording of 250.66 note #1. I was reading this as applying to only service entrance conductors on the line side of the meter in multiple sets. The reference to 230.40 cleared it up. Thanks to all for their input.
Trevor
OK, so now I think that I've got it. I was getting hung up on the wording of 250.66 note #1. I was reading this as applying to only service entrance conductors on the line side of the meter in multiple sets. The reference to 230.40 cleared it up. Thanks to all for their input.
Trevor
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
Re: 250.66
I've just read note #1 for the 10th time and now I'm still not so sure. I will have to think about this today and post my thoughts later. I'm pretty good at english but the last 14 words of note #1 still have me vacillating between two thoughts.
I've just read note #1 for the 10th time and now I'm still not so sure. I will have to think about this today and post my thoughts later. I'm pretty good at english but the last 14 words of note #1 still have me vacillating between two thoughts.
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