Grounding detail information

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dduffee260

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Texas
I have a service that is 3000 amps. We have a main switchboard with a 3000 amp main circuit breaker. We have to go to the rebar, the building steel, the copper water line and a 3/4" x 10ft ground rod. The rebar is going to be 5/8". The MCB is about 80ft from the copper water line. We have 8 runs of 500 kcmil feeding the MCB.

I am a little lost as to what goes where. Table 250.122 says for a 3000 amp service to use 400 kcmil copper. Do we start at the cold water main coming into the building, then go to the main switchgear, then to the building steel with a continuous run of 400 kcmil copper? Then run from the ground rod with a #6 copper? Do they make an exothermic weld that goes to 5/8" rebar with a 400 kcmil copper? Can we go from the cold water pipe to the rebar, then back from the rebar to the switchgear? I though somewhere it says to use 3/0 copper for equipment ground.

There is a diagram that shows to attach a main bonding jumper from the grounded conductor to the ground bus. Then the connections to the other grounding but there is no size explanation. If I need to explain things different please let me know and I will try. Thanks guys for any help.
 
For a service use table 250.66 and look section 250.66 and its A, B, C
The GEC to the water line or it may be a bonding jumper will be full size, as will the GEC to steel. The GEC to rebar is not req to be larger than 4 awg and you don't need a ground rod. Lay out your runs to make the big GEC short and you can interconnect from the first 5 ft of water pipe, and use the bld steel to interconnct. You can also use aluminum if 18" from earth.
Post back with more questions and we'll assist.
 
dduffee260 said:
Do they make an exothermic weld that goes to 5/8" rebar with a 400 kcmil copper? Thanks guys for any help.


The largest condcutor required by 250.66 is #3/0 for the building steel and water pipe. For the CEE the largest condcutor required is #4. You can interconnect them in any convient way just ensuring that you don't end up with the #4 going to the electrodes that requires #3/0.


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