grounding questions

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  #1  
Old 10-11-01, 05:18 PM
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Question

I bought a house recently and I am needing to add grounded outlets several places. I am going to run green 12gage wire back to the breaker box for the grounds. Looking at how my box is grounded I have a question. My water meter is out at the street. The water supply line enters my house about 20 feet away from the box, but the box is grounded to branch line that is probably a good 50 feet in a loop off the main line. This is the only ground, there is no other wire going to a rod. Is this okay for the service ground?

Also on running the 12 gage ground wire back, I am assuming it is okay to run it back through the same junctions that the circuits go through and branch off of it to ground other outlets on the circuit. Must I run a separate ground wire back to the box for each circuit? Or Can I branch this one ground off onto other circuits? I am wondering, because the neutral bar in the fuse panel is almost full and I also need to add a couple of new circuits to the house.
Thanks for any information
 
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  #2  
Old 10-12-01, 08:20 AM
Wgoodrich
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If you have metal water pipe in direct contact with the earth and you have a grounding electrode conductor coming from the main panel to that water pipe connecting within 5' of the entrance of that water pipe into the structure then you would probably be approved as existing. The current NEC requires that you add a supplemental grounding electrode as a grounding source for that structure in case the water pipe is changed to plastic thus losing your grounding electrode system if that was done. If it were me I would add that ground rod as a supplemental grounding electrode and connect it in the main service rated panel meeting the current Code and ensuring that you have a grounding electrode system.

The NEC requires that you run an added green insulated equipment grounding conductor serving a branch circuit directly to the grounding bar of your panel or to the main water line within 5' of the entry of that water line into the structure only if that water pipe is used as a grounding electrode system as you say you have.

You are required a green equipment grounding conductor for each branch circuit serving receptacles without connecting to multiple circuits. Each branch circuit must have its own green equipment grounding conductor added and ran as closely to the existing branch circuit conductor as possible and connected as discribed above.

When dealing with equipment grounding conductors in a panel grounding bar you may stuff as many grounding conuductors in each screw connection as you like. White grounded or neutral conductors must be individually connected to a single screw. You can double up your equipment grounding conductors under the same screws of the grounding bar making room for more white neutral or grounded conductors to be added and singaly connected one per screw.

Hope this helps

Wg
 
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Old 10-12-01, 05:51 PM
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Thank you for the reply, From what I understand I need to move my ground strap on the service panel from where it is to within 5 feet of entering the house on the water feed line. That will mean running a 25 foot ground strap?
Thank you.
 
  #4  
Old 10-13-01, 03:00 PM
Wgoodrich
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Yep if that metal water pipe is in direct contact with the earth for a minimum of 10'

See the Article dictating that below;

250-50. Grounding Electrode System
If available on the premises at each building or structure served, each item (a) through (d), and any made electrodes in accordance with Sections 250-52(c) and (d), shall be bonded together to form the grounding electrode system. The bonding jumper(s) shall be installed in accordance with Sections 250-64(a), (b), and (e), shall be sized in accordance with Section 250-66, and shall be connected in the manner specified in Section 250-70.
An unspliced 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. It shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.
The grounding electrode conductor shall be unspliced or spliced by means of irreversible compression-type connectors listed for the purpose or by the exothermic welding process.
Interior metal water piping located more than 5 ft (1.52 m) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.
Exception: In industrial and commercial buildings where conditions of maintenance and supervision ensure that only qualified persons will service the installation and the entire length of the interior metal water pipe that is being used for the conductor is exposed.
FPN: See Sections 547-8 and 547-9 for special grounding and bonding requirements for agricultural buildings.
(a) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 10 ft (3.05 m) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or sections or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors.
(1) Continuity. Continuity of the grounding path or the bonding connection to interior piping shall not rely on water meters or filtering devices and similar equipment.
(2) Supplemental Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in Sections 250-50 or 250-52. Where the supplemental electrode is a made electrode of the rod, pipe, or plate type, it shall comply with Section 250-56. The supplemental electrode shall be permitted to be bonded to the grounding electrode conductor, the grounded service-entrance conductor, the nonflexible grounded service raceway, or any grounded service enclosure.
Exception: The supplemental electrode shall be permitted to be bonded to the interior metal water piping at any convenient point as covered in Section 250-50, Exception.
Where the supplemental electrode is a made electrode as in Section 250-52(c) or (d), that portion of the bonding jumper that is the sole connection to the supplemental grounding electrode shall not be required to be larger than No. 6 copper wire or No. 4 aluminum wire.
 
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