I am getting set to complete the grounding for a 1200a service on a job. I have a situation that I have not come across before. The water main enters the building approx. 200 feet from the main service. Is there any alternatives to use other than running a 3/0 the whole way between the gear and the valve? That is the plan right now but was wondering if there is another method to save time material but still remain code compliant. I have already completed the Cadweld to steel and grounding elctrodes. Thank you.
[This message has been edited by elektrikguy (edited 06-24-2005).]
Some jurisdictions will accept a bond from the service to the building steel, and then a bond from the steel to the water at the point where the water enters the building. It is a matter of how 250.50 is interpreted. Check with the local inspecting agency first. Alan
Alan-- If it was easy, anyone could do it.
Re: grounding main water question#93967 06/24/0502:44 PM06/24/0502:44 PM
thanks for the replies. I had heard the method of bonding to the steel before. EVERY service I have done has had the mechanical room next to or in close proximity to the main electrical room. I had run a pipe underground from the service to the valve but came to find out it had been dug up and my guys do not know what it was and let them keep backfilling. They told me they thought it was just some pvc someone had thrown into the ditch? Oh well...have a little work ahead of me. Again thanks.
Re: grounding main water question#93968 06/25/0511:37 AM06/25/0511:37 AM
Exception: In industrial and commercial buildings or structures where conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system, provided that the entire length, other than short sections passing perpendicular through walls, floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed.
If you could find a water pipe, and an inspector to allow it... That would be your best bet, other than running wire the whole way.
I did it a few years ago, 50' from the entrance, and the inspector had me chain a sign to the main water valve, and my connection to the pipe. And bond accross the main. I think the sign was something to the effect of "this portion of the water line is being used as electrical grounding conductor". The building has its own maintenance personel. The only reason we thought of it was that we would have to go through some heavy timber beams to get there.
Mark Heller "Well - I oughta....." -Jackie Gleason
Re: grounding main water question#93969 06/25/0512:20 PM06/25/0512:20 PM
Electricguy, is you service on the building interior or exterior? If it is on the exterior you can bond any exterior water pipe so long as it has a minimum of 10 feet of direct contact with the soil and you will still satisfy 250.52. What you cannot do in other than certain industrial buildings is clamp onto water pipe on the interior that is more than 5' from the place where it enters the building.
Re: grounding main water question#93970 06/26/0511:26 PM06/26/0511:26 PM
250.64(F) To Electrode(s). A grounding electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system or to one or more grounding electrode(s) individually
Basically you can run your GECs any way you want to, to create your grounding electrode system.
The handbook shows a nice picture of this in Exhibit 250.27. It has a GEC going from your service, to the cold water, then from a different section of the cold water it goes to building steel. From a different section of building steel it goes to a ground rod. Another section of the building steel attaches to the ufer. And another section of the building steel attaches to a ground ring.
As long as you don't use the provisions for smaller GECs like a ground rod while feeding your cold water you can do it anyway you want.
Except however, if the E.E. on your plans calls out for seperate runs from the service which they almost always do in commercial.