Uninsulated conductor in SE

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czars

Czars
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West Melbourne, FL
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Florida Certified Electrical Contractor
Does the NEC specify the size of the uninsulated (grounding) conductor in SE and USE with respect to the insultated conductors? For instance, 4/0 Al insulated conductors for a 200 A service are accompanied by a 2/0 Al uninsulated (grounding) conductor. Where or how is the size of the uninsulated conductor identified?
 
Uninsulated conductor in SE

Sorry, perhaps I didn't clearly state my question. Does the NEC identify how to size (not mark) the uninsulated (grounding) conductor in SE. For instance, for a 200 A residental service, one can use a 4 conductor cable containing 3 insulated 4/0 Al conductors and and uninsulated 2/0 (grounding) conductor. The 4/0 Al conductors are called for in Table 310.15(B)(6). Where or how is the size of the uninsulated conductor identified or called for.
 
czars said:
For instance, for a 200 A residential service, one can use a 4 conductor cable containing 3 insulated 4/0 Al conductors and and uninsulated 2/0 (grounding) conductor.
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This is still unclear as you mention a residential service but also mention a 4 conductor cable and a grounding conductor.

If you have a four conductor cable and it has a grounding conductor in it that it is not a service cable but a feeder. In that case it is sized by Table 250.122.

If this was a service cable than you would not have separate grounded and grounding conductors, you would have only the grounded conductor and in that case the size can be reduced per 220.22 (2002 NEC)
 
Uninsulated conductor in SE

Thanks IWIRE for your response. However, I feel that we still are not communicating.

For example: In Brevard County, FL a new residence with 200A service would be equipped with 3 conductors from the service point, through the meter can, to the service disconnect, if a service disconnect is required in accordance with 230.70(A)(1). If the service panel is located on the other side of the residence (in the garage for instance), cable type SE would typically be used to connect the service disconnect to the service panel. This cable consists of 3 insulated conductors (2 hot, 1 neutral) and an uninsulated grounding conductor. If Al conductors are used, the insulated conductors in the cable (cable manufactured by Alcan is popular) are 4/0 Al in accordance with Table 310.15(B)(6) and the uninsulated conductor in the Alcan cable is 2/0 Al.

Table 250.66 calls for a #2 Al grounding electrode conductor and Table 250.122 calls for a #4 Al grounding conductor. Yet the type SE cable contains a 2/0 uninsulated conductor. Why?

Does the NEC identify that the 2/0 uninsulated conductor (in this case of a 200 A service) is required and if so, how is the size of the uninsulated conductor computed with respect to the service size (e.g. 200 A) or the service conductor size (4/0 Al)?
 
czars said:
Thanks IWIRE for your response. However, I feel that we still are not communicating.
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That is possible. :)

For example: In Brevard County, FL a new residence with 200A service would be equipped with 3 conductors from the service point, through the meter can, to the service disconnect, if a service disconnect is required in accordance with 230.70(A)(1). If the service panel is located on the other side of the residence (in the garage for instance), cable type SE would typically be used to connect the service disconnect to the service panel. This cable consists of 3 insulated conductors (2 hot, 1 neutral) and an uninsulated grounding conductor.
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In the installation you describe above the four wire cable from the service disconnect to the panel is not a 'service cable' it is a feeder and the grounding conductor is sized per 250.122. in other words the grounding conductor is sized for the over current device ahead of the circuit.

There is no such thing as service cables, service conductors or service raceways on the load side of the service disconnect.

Between the utility service point and the service disconnecting means all the equipment and conductors are service equipment and conductors.

On the load side of the service disconnect are feeders and branch circuits.
 
I think it is based on an assumption of what size OCPD is normally associated with the feeder. Generally, a #2 SER will be on a 100A breaker, max. So, they assume.

For example, 6/3 romex is assumed to be placed on a 50A breaker, so they use a #10 EGC. If you were to place it on a 65A breaker for an A/C, then you'd be out of luck. You'd need a larger cable or a different method.
 
czars said:
Table 250.66 calls for a #2 Al grounding electrode conductor and Table 250.122 calls for a #4 Al grounding conductor. Yet the type SE cable contains a 2/0 uninsulated conductor. Why?
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Since the "worst-case" size is smaller than the 2/0 bare in 4/0 cables, it may be for reasons that only the manufacturer knows. Perhaps simple durability is why. In any case, I have no problem with an EGC almost as large as the feeder conductors; it's kinda reassuring.
 
I've seen feeders for mobile homes that contained two 4/0 AL, one 2/0 AL grounded (neutral) and one #4 AL for the grounding conductor.
These weres on a 200A feed from the outside main to the BP.
It was (factory) pre-twisted cable and all of the conductors were insulated.
steve
 
czars said:
Does the NEC specify the size of the uninsulated (grounding) conductor in SE and USE with respect to the insultated conductors? For instance, 4/0 Al insulated conductors for a 200 A service are accompanied by a 2/0 Al uninsulated (grounding) conductor. Where or how is the size of the uninsulated conductor identified?
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 Yes the NEC mandates the size of the equipment grounding conductor and the grounded (neutral) conductor as others have referenced in their post.

You mandate the size conductor that you purchase. Tell the supply house to order the cable in the sizes that you desire.

The supply house will stock the sizes that are most popular as your question seems to reflect.
 
If you were to use the ser cable as parallel (3x4/0=540amps) the eq grd would need to be 2/0 al. Am I overthinking this thing? Probably, I didn't get enough sleep last night.

Bob on the left coast.
 
I've always assumed SER was made as Service Entrance cable for a 3 phase service, so it would be for example 3 4/0 phase conductors and a 2/0 bare neutral, like SEU is used for a single phase service. That would explain the size of the bare conductor being larger than table 240.122 specifies.
 
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