CT Service grounding

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sparkyjpb

sparkyjpb

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S/E Michigan
I don't do much commercial and this job I'm quoting will only be the the 2nd with a CT cabinet. Here's the facts-school maintenance garage, upgrading the service from single phase 200 amp to single phase 400 amp, 1 meter on building, 3- 500's in 3" riser out of top of ct, gutter under ct, under gutter 2 disconnects 1-100 amp and 1-200 amp, pipe out to respective sub panels. What is the process of grounding? From each disconnect to ground rods? What about the water pipes bonding? Trying to expand a little, just need some help.
Thanks Guys
 
If you are using the neutral conductor for bonding of the C/T cabinet then I would terminate the Grounding Electrode Conductor in the C/T cabinet on the neutral lug and the service is grounded. See 250.24(A)(1)

Pete
 
What about 250-53 (E) stating where the supplemental electrode is a pipe, rod, or plate......shall not be required to be larger than 6 copper?
 
sparkyjpb said:
What about 250-53 (E) stating where the supplemental electrode is a pipe, rod, or plate......shall not be required to be larger than 6 copper?
Click to expand...
The rod will be your supplementary electrode a #6 is the maximum size require if it is suggested to fiscal damage you should use a #4. ,your main water ground will be based on the table 250.66.
 
correct me if im wrong.

correct me if im wrong.

pete m. said:
If you are using the neutral conductor for bonding of the C/T cabinet then I would terminate the Grounding Electrode Conductor in the C/T cabinet on the neutral lug and the service is grounded. See 250.24(A)(1)

Pete
Click to expand...


I dont think your CT metering cabinet is considered your "Service" My understanding is that you bond your neutral in the CT can to "ground the CT can" I do believe that you are supposed to bond your neutral in each of your 1-6 main disconnects and your grounding electrode conductor shall terminate in each. You are allowed to use the same grounding electrodes in each of your service disconnects.
 
Save your money!

Save your money!

sparkyjpb said:
I don't do much commercial and this job I'm quoting will only be the the 2nd with a CT cabinet. Here's the facts-school maintenance garage, upgrading the service from single phase 200 amp to single phase 400 amp, 1 meter on building, 3- 500's in 3" riser out of top of ct, gutter under ct, under gutter 2 disconnects 1-100 amp and 1-200 amp, pipe out to respective sub panels. What is the process of grounding? From each disconnect to ground rods? What about the water pipes bonding? Trying to expand a little, just need some help.
Thanks Guys
Click to expand...

Why spend an extra 120 bucks on that service conductor gutter? Your CT can will typically come with at least two sets of lugs per phase, stub two short PVC pipes (to avoid bonding bushings) into the tops of those mains sitting below your CT can. Dont worry about an equipment ground from your CT can to your mains either. Your grounding and bonding should be done from your mains to your grounding electrodes.
 
Rsteenson said:
I dont think your CT metering cabinet is considered your "Service" My understanding is that you bond your neutral in the CT can to "ground the CT can" I do believe that you are supposed to bond your neutral in each of your 1-6 main disconnects and your grounding electrode conductor shall terminate in each. You are allowed to use the same grounding electrodes in each of your service disconnects.
Click to expand...

The C/T can is required to be grounded and bonded. The neutral conductor can perform both of these functions. In the scenario I described if a properly sized grounding electrode conductor is routed to the C/T can it is permitted by section 250.24(A)(1) to attach to the neutral in the C/T can.

Once you have made this single point connection the service (see definition of service in article 100) is grounded.

The scenario you describe is permitted in 250.64(D) but that would result in more wire being used to accomplish the same objective which is to ground the service.

So, FWIW I don't think you are wrong I just think we have a different approach.:cool:

Pete
 
DARUSA said:
The rod will be your supplementary electrode a #6 is the maximum size require if it is suggested to fiscal damage you should use a #4. ,your main water ground will be based on the table 250.66.
Click to expand...

Just looked at job again and found that the water pipe feeding the building is plastic. Theres only a small portion of the plumbing that is copper. Do I just go to this short section or is it pointless?
 
sparkyjpb said:
Just looked at job again and found that the water pipe feeding the building is plastic. Theres only a small portion of the plumbing that is copper. Do I just go to this short section or is it pointless?
Click to expand...

If the water line meets the requirements in 250.52(A)(1) you must use it as an electrode. If it doesn't then you are not required to utilize it as an electrode (simply because it isn't).

Depending upon how much of the interior water piping is metallic you may have to bond it in accordance with 250.104(A) and the remaining sub-sections.

Pete
 
Thanks for the input guys, it's much appreciated. I learn a lot from just reading through this forum a few nights a week! I love it and the fact that everyone is willing to help others.
 
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