250.64(D)

[hhsting]

Attached sketch shows two sets of service entrance conductors connected from power company CT cabinet to trough then to each respective service disco. F1 service entrance conductor is sized 4#600kcmil and F2 service entrance conductor is sized 4#3/0 AWG.

Grounding electrode conductor G3 is sized #2 CU, G2 is sized #1/0 AWG. G2 and G3 connect G1 as shown. G1 is the common grounding electrode conductor which then bonds to steel and cold water pipe.

servic disco label B is 400A and service disco label C is 200A.

Questions:
1. How does one size G3? Area of 600kcmil + area of 3/0Awg and look at 250.66? If not then how?

2. Is CT connection to two separate service discos like attached allowed? No code violation.

 

[infinity]

The GEC G1 is sized according to the SEC's feeding the meter. G2 and G3 are taps to the GEC and are sized according to the conductors F1 and F2.

 

[david]

Determine if you have any service conductors in parallel

You do not

Determine the larges service conductor and start there

 

[david]

The GEC G1 is sized according to the SEC's feeding the meter. G2 and G3 are taps to the GEC and are sized according to the conductors F1 and F2.

Are you saying you define the service conductors supplying the meter as service entrance conductors?

 

[david]

Attached sketch shows two sets of service entrance conductors connected from power company CT cabinet to trough then to each respective service disco. F1 service entrance conductor is sized 4#600kcmil and F2 service entrance conductor is sized 4#3/0 AWG.

Grounding electrode conductor G3 is sized #2 CU, G2 is sized #1/0 AWG. G2 and G3 connect G1 as shown. G1 is the common grounding electrode conductor which then bonds to steel and cold water pipe.

servic disco label B is 400A and service disco label C is 200A.

Questions:
1. How does one size G3? Area of 600kcmil + area of 3/0Awg and look at 250.66? If not then how?

2. Is CT connection to two separate service discos like attached allowed? No code violation.

The common GEC is sized according to the service entrance conductors supplying a disconnect your largest conductor supplying a disconnect is 600 MCM

 

[infinity]

The common GEC is sized according to the service entrance conductors supplying a disconnect your largest conductor supplying a disconnect is 600 MCM

How do you know that the conductors supplying the meter are not larger than 600 kcmil?

 

[david]

How do you know that the conductors supplying the meter are not larger than 600 kcmil?

Not sure why that would matter,

would you agree that GEC are sized according to the largest service entrance conductor,

or in the case where there are no service entrance conductors based on the size of the service entrance conductor that would be required to supply the building

 

[electrofelon]

Are you saying you define the service conductors supplying the meter as service entrance conductors?

I dont see anything in the definition that says a meter/CT is the starting point of the service entrance conductors (unless that is the service point).

Edit: upon further analysis, I would say for underground, the meter/CT is the beginning of the service entrance conductors, but for overhead it is not.

 

[david]

No ,

but two things we do know service entrance conductor are the conductors that enter a building

Or are sized based on the conductors if they did enter the building , sized required to supply the building load
Also they end at a splice or tap point usually out side clear of the building walls

 

[david]

looking at the information note there are many services that do not have service entrance conductors, what they do have is service conductors

 

[david]

All of that really doesn’t matter 250.64 (D)
Multiple disconnecting means in separate enclosures

states the largest ungrounded conductors supplying a disconnect

 

[electrofelon]

Also they end at a splice or tap point usually out side clear of the building walls

keep going: "......where joined by tap or splice to the service drop or overhead service conductors."

I dont think this really matters to the OP however.

 

[david]

I dont think this really matters to the OP however.

The OP would use 600 MCM to size the GEC

keep going: "......where joined by tap or splice to the service drop or overhead service conductors."

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

On most services a portion of the service conductors enter the building

The meter is a point that the service conductors are tapped or spliced depending on the service

Service entrance conductors usually outside to a splice or tap point (Meter) where there are tapped or splice conductors. The tapped or spliced conductors ties in to the service drop on a overhead service

Under ground services are the same the service entrance conductors usually take you to a meter (tap or splice point)

 

[electrofelon]

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

On most services a portion of the service conductors enter the building

The meter is a point that the service conductors are tapped or spliced depending on the service

Service entrance conductors usually outside to a splice or tap point (Meter) where there are tapped or splice conductors. The tapped or spliced conductors ties in to the service drop on a overhead service

Under ground services are the same the service entrance conductors usually take you to a meter (tap or splice point)

IMO the wording is poor and it is not clear. Do you consider a "riser" from the line side of a meter, up to a weather head (which is the service point) to be "service conductors, overhead"?

 

[david]

IMO the wording is poor and it is not clear. Do you consider a "riser" from the line side of a meter, up to a weather head (which is the service point) to be "service conductors, overhead"?

Yes
how else would the information note make any sense

 

[electrofelon]

Yes
how else would the information note make any sense

The information note appears to be for the underground system. I dont know why the wording is so much different in service conductors underground vs service conductors overhead, it doesnt make much sense.

IMO most overhead services do not have "service conductors, overhead" and the service entrance conductors connect directly to the service drop. Thats the way I read it, YMMV.

 

[infinity]

The information note appears to be for the underground system. I dont know why the wording is so much different in service conductors underground vs service conductors overhead, it doesnt make much sense.

IMO most overhead services do not have "service conductors, overhead" and the service entrance conductors connect directly to the service drop. Thats the way I read it, YMMV.

That is my take on it too although the wording of the various definitions is poor. I based my initial responses on that.

 

[david]

MERRY CHRISTMAS (Mark 8:29 )

250.66 note 2 tells us what to do when the service equipment has no service entrance conductors

There is an information note following service entrance conductors that tells us there are services that do not have service entrance conductors

There are thousands of services where the service conductors change size in a CT or meter enclosure

We all can agree that the meter is the first tap or splice point after leaving the building
It really doesn’t matter what the conductors are called in applying the OP question

To your point in applying 250.64 (D) the service conductors from the service drop to the meter do not need to be the same size as the service conductors that enter the building and supply the service disconnect.

That is my take on it too although the wording of the various definitions is poor. I based my initial responses on that.

250.64 (D) clearly states the common GEC is sized based on the largest service conductors that supply a disconnect of the multiple disconnects that make up the service equipment

 

[david]

IMO most overhead services do not have "service conductors, overhead" and the service entrance conductors connect directly to the service drop. Thats the way I read it, YMMV.

250 64 (D) does talk about what to do when the service entrance conductors connect directly to a service drop

There is a small Borough called wampum not far from here, they have there own co-op and sale and maintain the utility supply that they purchase off a large utility company,

You don’t see it much anymore but they are going to allow the meters to remain inside the building second floor landing.

In that situation the service entrance conductors make a direct connection to the service drop

250.64 (D) states (if) the service entrance conductors connect directly to the service drop than go to Table 250.66 note 1
Table 250.66 note 1 starts out if………….connect directly to………………..

There are times that the service entrance conductors do connect directly to a service drop

It really doesn’t matter what we call portions of the service conductors but Imo the portion of the service conductors that enter a building are the service entrance conductors

 

[kwired]

MERRY CHRISTMAS (Mark 8:29 )

250.66 note 2 tells us what to do when the service equipment has no service entrance conductors

There is an information note following service entrance conductors that tells us there are services that do not have service entrance conductors

There are thousands of services where the service conductors change size in a CT or meter enclosure

We all can agree that the meter is the first tap or splice point after leaving the building
It really doesn’t matter what the conductors are called in applying the OP question

To your point in applying 250.64 (D) the service conductors from the service drop to the meter do not need to be the same size as the service conductors that enter the building and supply the service disconnect.




250.64 (D) clearly states the common GEC is sized based on the largest service conductors that supply a disconnect of the multiple disconnects that make up the service equipment

Wouldn't an example of where you don't have "service entrance conductors" be a situation of maybe having bus bars instead of art 310 conductors used as the service entrance conductors? Otherwise most other incidents you would have a conductor that is listed in the table.