Sizing GEC for Overhead Service

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Dansos

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We are replacing an existing 100A Main Breaker load center in a multi family building. There are (5) meter sockets on the building BUT they are not in 1 meter stack and they have separate SEU cables feeding them. 2 meters have 4/0-4/0-2/0SEU 2 meters have 4/0-4/0-2/0 SEU and the meter we are working on has a 2/2/4 SEU Cable feeding it. I’ve always sized this off the conductor size of the feeders but I’m not sure how to figure this out.
250.66 chart is what I have always used for this but I’m not sure it would apply to this or not.
 
Are the SEU cables fed from one service - i.e. one connection point to the utility's wiring - or are there multiple services?

Put another way, do you have multiple service conductors or just multiple service entrance conductors?
 
jaggedben said:
Are the SEU cables fed from one service - i.e. one connection point to the utility's wiring - or are there multiple services?

Put another way, do you have multiple service conductors or just multiple service entrance conductors?
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The SEU cables connect to a single cable coming from the pole on street. The cable coming to house is only a 4/0-4/0-2/0 and that is ran by the poco.
 
electrofelon said:
assuming you are using the grounding electrode conductor tap method, the tap would be sized to the conductors serving that service disconnect.
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There is #2 serving MY service disconnect. Would the additional wires for the other meters be ignored in this situation. ?
 
I think you could run a #6 from your disconnect to the grounding electrode and not worry about the others if they are grounded seperately. What GEC(s) are there now? What electrode(s)?

For GEC taps or separate GECs, both allowed, the size would be based on the conductors to the respective disconnect. Where they all combine to one GEC to the grounding electrode system, that GEC would have to be based on the combined cross sectional areas of all the service entrance conductors.
 
jaggedben said:
I think you could run a #6 from your disconnect to the grounding electrode and not worry about the others if they are grounded seperately. What GEC(s) are there now? What electrode(s)?

For GEC taps or separate GECs, both allowed, the size would be based on the conductors to the respective disconnect. Where they all combine to one GEC to the grounding electrode system, that GEC would have to be based on the combined cross sectional areas of all the service entrance conductors.
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Ok thank you for the info. They currently have a #4 Cu running from the water main to one of the panels. Then they have each panel jumped with a #4 Cu. I thought that was undersized for a GEC but figured we would just worry about running a SEPARATE #6 cu to the water main and only worrying about our disco
 
Dansos said:
Ok thank you for the info. They currently have a #4 Cu running from the water main to one of the panels. Then they have each panel jumped with a #4 Cu. I thought that was undersized for a GEC but figured we would just worry about running a SEPARATE #6 cu to the water main and only worrying about our disco
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Read through 250.64(D). Jumping/looping between panels with a gec does not seem to be a compliant method. I don't know why so many people struggle with grounding services with multiple enclosures, it's pretty clearly laid out in the section I mentioned.
 
Dansos said:
Ok thank you for the info. They currently have a #4 Cu running from the water main to one of the panels. Then they have each panel jumped with a #4 Cu. I thought that was undersized for a GEC but figured we would just worry about running a SEPARATE #6 cu to the water main and only worrying about our disco
Click to expand...
#4 copper GEC is okay if based on 4/0 aluminum. I don't think you mentioned if the SEU are copper or aluminum conductors. But if aluminum Nd I understand your description correctly, if there were a #4 copper GEC from each panel directly to the water pipe that sounds fine.
 
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