GEC in Service Lateral between Remote Main And SwG

[DonaldSparkyDog]

On a project for the water co, the main service riser is rack mounted on a pole with an overhead drop. The 600a MDS is on the same rack. From there an UG feeder to the control bldg. switchgear contains the phase and the sized GEC for line side SI conductors instead of EGC sized for the 600a fuse. Does the NEC dis-allow this? The GE system is in the control building.

 

[lielec11]

On a project for the water co, the main service riser is rack mounted on a pole with an overhead drop. The 600a MDS is on the same rack. From there an UG feeder to the control bldg. switchgear contains the phase and the sized GEC for line side SI conductors instead of EGC sized for the 600a fuse. Does the NEC dis-allow this? The GE system is in the control building.

Based on 250.66 I believe the that you are required to size the GEC based on the line side service entrance conductors and not the size of the 600A MDS. In the 2008 handbook take a look at the calculations example on page 229-230.

 

[infinity]

If the service disconnect is at the pole then as you've sated you have an underground feeder to the separate structure. That would make the conductor run with the feeder an EGC sized as with 250.122. If you sized it as a GEC it would probably be larger than the required EGC.

 

[DonaldSparkyDog]

The question is..... since the GEC System is established at the remote building but the service main disconnect is out at the riser pole I interpret the code to say that the bonding of the main service disconnect would have to be run in the underground main feeder conduit from the building out to the pole...therefore the phase wires would run with a grounding conductor as usual but it would need to be sized as a GEC not an EGC, this would provide two items at once; 1) the EGC from the service disconnect towards the building and 2) the GEC from the established grounding electrode system in the building towards the service disconnect. By doing this there would be one less conductor between the two locations because the GEC is serving two purposes. Anyone disagree?

 

[texie]

The question is..... since the GEC System is established at the remote building but the service main disconnect is out at the riser pole I interpret the code to say that the bonding of the main service disconnect would have to be run in the underground main feeder conduit from the building out to the pole...therefore the phase wires would run with a grounding conductor as usual but it would need to be sized as a GEC not an EGC, this would provide two items at once; 1) the EGC from the service disconnect towards the building and 2) the GEC from the established grounding electrode system in the building towards the service disconnect. By doing this there would be one less conductor between the two locations because the GEC is serving two purposes. Anyone disagree?

Incorrect. The remote service will need a GES and bonded neutral. The run to the building is a feeder as Infinity mentioned and must have an EGC sized per 250.122. At the building end of the feeder you must have another GES but not bond the neutral. See 250.32.

 

[david luchini]

The question is..... since the GEC System is established at the remote building but the service main disconnect is out at the riser pole I interpret the code to say that the bonding of the main service disconnect would have to be run in the underground main feeder conduit from the building out to the pole...therefore the phase wires would run with a grounding conductor as usual but it would need to be sized as a GEC not an EGC, this would provide two items at once; 1) the EGC from the service disconnect towards the building and 2) the GEC from the established grounding electrode system in the building towards the service disconnect. By doing this there would be one less conductor between the two locations because the GEC is serving two purposes. Anyone disagree?

I disagree. I think you need a separate grounding electrode system at each location.

An equipment grounding conductor should be run with the feeder from the main disconnect to the building. The egc should be bonded to the grounding electrode system at the building, per 250.32(B)(1).

Edit: ...or what texie said.

 

[infinity]

Incorrect. The remote service will need a GES and bonded neutral. The run to the building is a feeder as Infinity mentioned and must have an EGC sized per 250.122. At the building end of the feeder you must have another GES but not bond the neutral. See 250.32.

I agree. Each strucutre get's it's own GES, the stucture fed by the feeder has the "floating" neutral with the GES connected to the feeder EGC and the equipment not the neutral.

 

[GoldDigger]

The single conductor will serve as EGC and as the bonding jumper between the two sets of electrodes. I do not see an explicit size requirement for the second function though. I guess it depends on whether you see it as one large GES or two independent GES incidentally connected by a required EGC.

 

[infinity]

Digger brings up a good point, how do you size the GEC's at the remote structure which is fed by an EGC within a feeder, T250.122? Or are they not GEC's?

 

[david luchini]

Digger brings up a good point, how do you size the GEC's at the remote structure which is fed by an EGC within a feeder, T250.122? Or are they not GEC's?

The GEC is sized per 250.66.

 

[jtinge]

Do you have a single-line sketch of the installation? May aid in the discussion by clarifying terminology.

Does the switchgear have a main OCPD and are you treating the switchgear as a service entrance equipment or a building disconnecting means?

Once you identify the service conductors and feeders, you can easily identify GEC's, main/system and supply-side bonding jumpers, and EGC's and their locations and know which code sections come into play.

Based on 2014 NEC, 250.66 for GEC's, 250.102 for bonding jumpers, and 250.122 for EGC's. Where to locate the main or system bonding jumper will depend on service or feeder.

 

[Smart $]

Digger brings up a good point, how do you size the GEC's at the remote structure which is fed by an EGC within a feeder, T250.122? Or are they not GEC's?

GEC's at remote building are sized per 250.66 according to the largest feeder conductor.

 

[DonaldSparkyDog]

OK here is the question...Can the GEC sized conductor that is in the feeder between a service pole and a control building, which is larger than an EGC, be utilized as the EGC AND the GEC. The pole will NOT have the building steel, the ground ring, the water pipe and the concrete encased rebar which estabishes the GE system. It WILL have a ground rod. Can the GEC also be the EGC?

 

[augie47]

The GEC is sized per 250.66.

I agree based on 250.32 (E). 250.66 based on the ungrounded supply conductor.

 

[david luchini]

OK here is the question...Can the GEC sized conductor that is in the feeder between a service pole and a control building, which is larger than an EGC, be utilized as the EGC AND the GEC. The pole will NOT have the building steel, the ground ring, the water pipe and the concrete encased rebar which estabishes the GE system. It WILL have a ground rod. Can the GEC also be the EGC?

No, the conductor cannot be an EGC and a GEC.

You will have TWO GE systems, one at the pole and one at the building. The ground rod at the pole is the GE system for the pole location, though a single rod will need a supplemental electrode per 250.53(A)(2). The conductor run with the feeder from the disconnect to the building is an EGC, as required by 250.32(B)(1)

 

[lielec11]

I agree based on 250.32 (E). 250.66 based on the ungrounded supply conductor.

The largest ungrounded supply conductor would be the feeder conductors, or those conductors from the pole?

 

[texie]

The largest ungrounded supply conductor would be the feeder conductors, or those conductors from the pole?

Based on the largest ungrounded conductor of the feeder.

 

[DonaldSparkyDog]

No, the conductor cannot be an EGC and a GEC.

You will have TWO GE systems, one at the pole and one at the building. The ground rod at the pole is the GE system for the pole location, though a single rod will need a supplemental electrode per 250.53(A)(2). The conductor run with the feeder from the disconnect to the building is an EGC, as required by 250.32(B)(1)

Art. 250.58 Common GE... says that where fed from a separate feeder the same GE must be used. I take that to mean you are to have only one GE system...art. 250.64D3 allows a common location for connection of the GEC to the Grounded conductor. Art. 250.24A1 indicates that the connection of the GEC is to be made at the service disconnecting means at the point the grounded service conductor is connected. In this case there is no neutral loads only 3 phase, so after the service riser there is no neutral. What I'm interested in is if the GE system is at the common location in the building and you install a GEC to the service disconnecting means to connect to the service riser neutral to establish the Grounded Conductor as a fault return path to the electric co transformer bank, and then install a EGC all in the same feeder conduit with the phase conductors (3ph 3 w) is that not an overkill on copper having both an GEC AND a EGC? I have not found verbiage that prohibits having the GEC serve as two different conductors.

 

[david luchini]

Art. 250.58 Common GE... says that where fed from a separate feeder the same GE must be used. I take that to mean you are to have only one GE system...art. 250.64D3 allows a common location for connection of the GEC to the Grounded conductor. Art. 250.24A1 indicates that the connection of the GEC is to be made at the service disconnecting means at the point the grounded service conductor is connected.

250.28 says that when an ac system is connected to a grounding electrode in or at a building or structure, the same electrode shall be used to ground equipment IN or ON THAT building or structure.

In other words, everything associated with a single building or structure shall use the same grounding electrode.

You have TWO SEPARATE structures, the pole and the building. EACH building or structure requires it's own grounding electrode system.

250.64(D)(3) does not apply to your described installation.

What I'm interested in is if the GE system is at the common location in the building and you install a GEC to the service disconnecting means and the install a EGC all in the same feeder with the phase conductors (3ph 3 w) is that not an overkill on copper having both an GEC AND a EGC I have not found verbiage that prohibits this to occur.

250.50 requires that you install a grounding electrode system at the pole. 250.24 requires that you connect the grounded service conductor to the grounding electrode at the pole via an EGC. There is no purpose to having an EGC run with the feeder from the disconnect to the building.

 

[Smart $]

...250.24 requires that you connect the grounded service conductor to the grounding electrode at the pole via an EGC*. There is no purpose to having an EGC run with the feeder from the disconnect to the building*.

*Not with an EGC... but rather in the service disconnecting means with an MBJ (Main Bonding Jumper).

*EGC is required with the feeder to the building, because the grounded conductor is not bonded to either EGC or GEC at the building. In much older editions, an EGC was not required, but the grounded conductor was required to be bonded to both EGC or GEC at the building. An adequate ground fault current path is the reason.