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Grounding a home addition


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Summary: Electrical Grounding Question: Dave, We added an 1191 sq ft addition and I always intended on adding a new panel because the one currently installed does not have enough circuits and it is only 100 A.

Electrical Troubleshooting: Grounding a home addition



Electrical Troubleshooting Question:
Dave, We added an 1191 sq ft addition and I always intended on adding a new panel because the one currently installed does not have enough circuits and it is only 100 A. The city I live in does not do the electrical inspection so they just make sure there are smoke detectors. The state will do my electrical inspection. The panel board is about 20 ft away from where the addition starts so it never occurred to me that I would have to run a length of number 4 copper that far when my water pipe for the well is right next to the panel board.

I thought with two ground rods and the water pipe I would be fine. The problem is we are NOT required to use rebar in the footing and a lot of contractors do not do it to save money. So if I would have kept my mouth shut I would be fine. My question really boils down to this: Does the NEC give an order of precedence for the grounding scheme used? Section 250.52 of the 2002 NEC(I know its old but I have not had the heart to pay $90 for the 2008 version) lists several electrodes that are permitted but I am having a hard time finding where it states that I MUST use a certain method. If it were a safety issue then the state would require rebar in the footings and the connection must be made there. If they push this I am hoping since I have not poured the slab yet I can run 20 ft of rebar before we pour the slab and then run the #4 the 20 ft to make the connection. If the slab is more the 2 inches thick and is in direct contact with the ground I should be ok. However since I am installing radiant floor heating my slab will not be in direct contact with the ground but I could leave enough room to include 20 ft of rebar embedded in the concrete with that section of the concrete in direct contact with the ground. I did not read anywhere where it tells me if I have to have a minimum sq footage of concrete in contact with the ground. By the way I am doing the electrical work and since I was told by three electricians I could use the ground rods I thought I was ok. Hopefully I dodged the bullet by not pouring my slab yet. The code official made it sound like it HAD to be in the footing but I am reading the code as I only need to have 20 ft of rebar in the concrete and a portion of the concrete must be in contact with the ground not necessarily all of it. If you want/need more info let me know. I think what messed me up was the advice from the electricians and the fact an electrical plan was not required

I will contact the concrete guy and see if he left a connection but I doubt he did. You are going to like this, I was just told that I have to run a #4 copper ground wire 20 ft to the rebar that is in the footing of the addition we just put on. I spoke with three electricians up here and all of them told me to get grounds. What is worse if I would not have told the guy we put footings in then I would not be required to use them. Contractors are not required to install rebar in the footings. I have no idea what I am going to do and I will have a 20-30 ft copper ground wire running through my home, down the wall and in to the footing. You may want to add that bit of info to the website.
Thanks, Eric.

Hi Eric - I'm assuming that with your addition there was an electrical panel installed, or an upgrade, which would have caused the inspector to investigate the need for the bonded ground. I can't help but have a few questions, yet I am not totally aware of the details of your project. Typically the approved plan set will indicate which type of ground should be installed for a new home, and it is typically a ufer ground consisting of a 20 foot #2 rebar that is tied to the bottom bundle of rebar and the end would be above the foundation below the panel location, or for a 200 amp panel a #4 solid bare copper wire installed into the foundation which is tied to the bottom bundle of rebar which is 20 feet inside the foundation and then extra length would be leading out of the foundation and up to the panel location. At the jobsite, the electrician usually makes sure that this is installed before the foundation is poured and is verified by the inspector. I can provide more about grounding, but first I would like to know more about your project.



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