Sizing grounding conductors/bonding jumpers

Status
Not open for further replies.
joeyww12000

joeyww12000

Senior Member
Location
Chatsworth GA
I need some clarification on when to fully size grounding electrode conductors. Im bonding together building steel, concrete incased electrode, water pipe and a groundrod. First off Im coming in after someone to finish this and the way the pipes are ran is a small challenge since some wire has been pulled already. You have a 600a disconnect outside where they connected the grounded conductor to the can via bonding screw and out to a groundrod and a concrete encased electrode with a 2/0 cu. From the disconnect to the MDP no grounding conductor is pulled, only 3 phase conductors and a grounded conductor. I need to bond my steel and waterpipe inside the building. What size grounding conductor do I need to get from the grounded and grounding conductor bonding point inside the disconnect inside the building to the steel and water pipe?
 
joeyww12000 said:
You have a 600a disconnect outside where they connected the grounded conductor to the can via bonding screw and out to a ground rod and a concrete encased electrode with a 2/0 cu.
Click to expand...
A little overkill to run 2/0 to the ground rod and CEE but perfectly legal. NEC compliant would be a #6 to the rod and a #4 to the CEE but the engineer may have speced the 2/0.

From the disconnect to the MDP no grounding conductor is pulled, only 3 phase conductors and a grounded conductor.
Click to expand...
If this is in metal conduit then it is also legal.

I need to bond my steel and water pipe inside the building. What size grounding conductor do I need to get from the grounded and grounding conductor bonding point inside the disconnect inside the building to the steel and water pipe?
Click to expand...
What size are your service entrance conductors then look at 250.66 along with the notes under the table. I suspect the 2/0 is the size for the water pipe and steel.
 
I agree with Dennis, we need more information.

What size service entrance conductors do you have?

What type of conduit do you have running from the disconnect to the MDP?

Chris
 
joeyww12000 said:
I need to bond my steel and waterpipe inside the building. What size grounding conductor do I need to get from the grounded and grounding conductor bonding point inside the disconnect inside the building to the steel and water pipe?
Click to expand...
Don't those electrode conductors all have to land in the outside disco enclosure?

And shouldn't the neutral be left unbonded in the inside disco enclosure?
 
I have different responsibilities on this job, fire alarm and other low volt wiring. I just happened to see these problems when I was checking on the progress of the other workers. The service is a 600a, with 2 sets of 4-350cu parallel conductors. These go to 600a disconnect in PVC and out to MDP in PVC. Specs call for steel, water pipe, concrete encased rebar and a groundrod to be bonded in MDP, but no provisions were made. At the disconnect you have a 2/0 cu terminated to the grounded conductor lug with the grounded conductor, the grounding conductor continues out of the disconnect to a groundrod then to rebar in the footer. The disconnect inclosure is bonded by a bonding screw. From the disconnect into the MDP there are 2 sets of 4-350cu conductors. The grounded conductors are terminated to the grounded conductor lugs on one side of the MDP. There is another set of lugs bonded to these same lugs on the other side of the MDP enclosure that someone has terminated the EGC's going out to other sub panels fed from the MDP. In the subpanel every EGC and grounded conductor are bonded together!! Please tell me this isnt right.... I know its not. If they were to bond the disconnect enclosure only with the existing 2/0cu out to the groundrod this would unbond the grounded conductor at the disconnect making it OK to then bond at the MDP. This leaves some things that are not correct such as there will be no grounding electrode/groundrod for the service other than the one at the disconnect which is doing nothing but bonding the disconnect enclosure. Theres probably some more things wrong here and Ive wrote to much......Ill set back and get advice here.
 
Last edited:
You are correct in your thought that "this is not right". Your 600 amp disconnect is your service disconenct and should be the terminating point for all grounding electrodes.
With parallel 350's , 2/0 would be the correct electrode conductor size(however GECs going only to the rebar could be as small as #4, and to the rod as small as #6). A minimum #1 should have been installed from your 600 amp disconnect to the MDP as equipment grounds and the equipment grounds for sub-panlels tied to those.
The neutral & grounding should not be connected together in MDP.
 
Grounding and Bonding

Grounding and Bonding

Joey,

Anytime you have to fix someone else's work, it's a challenge. Be very careful and thorough with this installation because it sounds like the specs. are incorrect and you are getting into a sticky situation. Were the plans sealed by an engineer? Were the plans reviewed and approved by the local authority? Even though they are incorrect, some inspectors will insist the completed work match the plans because they pass off the liability to the engineer.

"Specs call for steel, water pipe, concrete encased rebar and a groundrod to be bonded in MDP, but no provisions were made."

All you need is one #4 from concrete encased rebar to disconnect and 2/0 to cold water and you can use bonding jumpers to your building steel and rod. Don't forget to jump out water meter and leave plenty of slack for meter removal. The disconnect in your case is the ONLY place where the grounds and neutrals come together. After that grounds and neutrals are seperated and isolated from each other. Make sure there is no bonding jumper in the MDP.

Follow Augie's advice on the rest. I can't believe how many times I see this where the EC doesn't pull an equipment grounding conductor when the main disconnect is outside. They think all they need is the neutral. :confused:

You really need to order Mike Holt's book on Grounding vs. Bonding because you are confusing the two. The book has 300 illustrations. Good Luck!
 
I do understand the correct installation and am learning more everyday.....but I am not the foreman, I have been in a leadman position but foreman thought he was to smart to accept any input from anyone under him in the food chain...this installation is not how I would have done it, but its ultimately none of my business.......since noone is going to change anything because of what I say...theres to much wire that has been pulled already....they will wait and see if it passes before changing anything....the reason Im on here so much is to assure my knowledge....this service installation has nothing to do with me...I looked at it for my own personal improvement....I knew it wasnt right and I went through the process of how to fix it if it were up to me....this website is a great learning tool....Im just waiting for my turn to run jobs and do them right.
 
Status
Not open for further replies.
Top