Grounding Electrode Conductor

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Liteitup

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Trying to figure out a job. It's a 6-family building. 7 meters, 60A subs and one 200a disconnect. I'm thinking #4AWG to the water main and 2 ground rods 6' apart. Do I have to run a separate (#6) wire back to the disconnect? Can I just run it to the water main?
 
Liteitup said:
Trying to figure out a job. It's a 6-family building. 7 meters, 60A subs and one 200a disconnect. I'm thinking #4AWG to the water main and 2 ground rods 6' apart. Do I have to run a separate (#6) wire back to the disconnect? Can I just run it to the water main?
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If you run a #4AWG From your main disconnect to your water main you should be fine:)
 
Liteitup said:
Trying to figure out a job. It's a 6-family building. 7 meters, 60A subs and one 200a disconnect. I'm thinking #4AWG to the water main and 2 ground rods 6' apart. Do I have to run a separate (#6) wire back to the disconnect? Can I just run it to the water main?
Click to expand...

You can run the #6 from the ground rods to the water main or set the rods by the disconnect and tie into the disco. With the #4 to water main you might get by with one rod.
 
There are several ways to do this. You could run separate GEC's back to the disco from both the rod(S) and the water pipe or you could run a properly sized GEC to one of the electrodes and then install a bonding jumper to the other electrode(s). You would need two rods if one rod has a resistance of more than 25 ohms.

Here's a graphic. Basically you're trying to create a grounding electrode system (GES) by bonding everything together.

1113918256_2.jpg
 
The size of the GEC to the metal underground water pipe must be sized to T250.66 and is based on the size of the largest ungrounded service-entrance conductor. You have not indicated in you pst what the rating and size of the service is nor what the size of the service entrance conductors are.

On a side note, do you have a main serivce disconnect? Your description reads like it might be a 230.71(A) violation???
 
Liteitup said:
Trying to figure out a job. It's a 6-family building. 7 meters, 60A subs and one 200a disconnect. I'm thinking #4AWG to the water main and 2 ground rods 6' apart. Do I have to run a separate (#6) wire back to the disconnect? Can I just run it to the water main?
Click to expand...

I would be surprised if there is no rebar in the footings or foundation (assuming this is new construction). If there is 20' or more of rebar in the footing or foundation, 250.50 requires you to use that as a grounding electrode. That and the metal water line is all you need. If you have the concrete encased electrode there is no need to drive ground rods.
 
Liteitup said:
It's a 6-family building. 7 meters, 60A subs and one 200a disconnect.
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Really? I'm sure you've done a load calc, and I don't get into this very much but 60A x 7 = 420A. :confused:

eprice said:
If there is 20' or more of rebar in the footing or foundation, 250.50 requires you to use that as a grounding electrode.
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What do you do when you literally have it "in the footing or foundation," meaning it's already encased. Hard to attach to it then, no? What's normally done here?

Thx
 
jetlag said:
Agreed but less than 30 amp per unit sounds awfully low , dont they have to have at least electric A/c . 2- 20amp kitchen c top . Lights and recepts ?
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That's why we do load calculations, and not make wild guesses based on circuit ratings.
 
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