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John318 11-16-2011 07:44 AM

Proper Water and Gas line bonding. Sub Panel OK?
I live in a home built in the mid 60s. Originally there was only a fuse panel located within a clothing closet and all outlets/fixtures were connected with two wire NM with no ground. At some point a panel was added outside to accommodate an addition. All large appliances were added to the new panel, which is full. Other than the large appliances and the new addition, the original portion of the home was left attached to the fuse panel.

I have replaced the fuse panel with a sub panel, which has been moved to a utility room and out of the closet. I have also been systematically rewiring each room with new NM so that I have a ground for all outlets/fixtures.

Last night I began running new wire to the gas furnace and noticed the following: the original non grounded wire ran behind the furnace to a receptacle box, which is inaccessible. A new furnace was installed 5 years ago. A new piece of NM was tied into the receptacle box and run to a new receptacle which was in a more convenient location for the new furnace. However, this receptacle was obviously not grounded either. There was a green wire attached to the gas line before it entered the furnace and the run into the new outlet and attached to the grounding screw of the receptacle. As far as I can tell, this provided no real benefit. There was no ground wire at the receptacle.

I have run a new circuit for the furnace, so the receptacle is now grounded. Do I need to attach that green wire from the gas line to the ground in the receptacle box? OR...

I have noticed that my water lines are not bonded anywhere either. There is a hot water heater 3 ft from my new sub panel. Can I just bond all three (hit, cold, gas) lines from the water heater to the sub panel ground bar? The panel is fed with 4/3 romex and has a #6 ground wire to the main panel, which is 100 amp service.

Note: There is a small section of flexible gas line between where the gas line drops from the ceiling and where it enters the furnace. It is gray. I know nothing abut this sort of line and am not sure if the prevents the gas line from being bonded by default through the furnace.

Since you've already had the patience to read this far, let me ask one more simple question: I understand the difference between bonding and grounding as this: Bonding means ensuring an electrical charge can escape via the existing ground back to the main panel, correct? Thus a bonded line would be wires to the ground/neutral bus on the main (or in my case, ground bar in the sub) panel. Grounding would be running all grounds to the water line and no where else, correct? I know this causes confusion to a lot of folks. I want to be sure I am understanding this correctly.

autx790 11-16-2011 10:22 AM

I believe the propper way to bond your gas line is to run at least a 6 guage ground wire from the gas line (close to the meter) and then to the ground rod for the house. I'm not sure if water lines need to be bonded.

AllanJ 11-16-2011 10:43 AM

The water line entering the basement, if metal, counts as a grounding electrode and you run a #6 gauge copper wire (#4 gauge for service over 100 up to 200 amps, #2 for larger services) from it (within 5 feet of where it enters and also before the meter. This wire must be unspliced to the panel neutral bus if there is not already an unspliced wire from the panel to a ground rod.

Metal water and drain pipes up in the house and separated from the basement plumbing with plastic pipes should be bonded although you don't have to break open the walls and make a rush job out of this. Use a ground wire at least as thick as any of the electrical circuit wires passing near those metal pipes.

The gas line does not count as a grounding electrode but should also be bonded to the panel neutral gus with a #6 copper wire. If this latter wire reaches one of the other fat ground wires first it can end and be clamped on there. But this ground wire can be omitted if at least one gas appliance uses electricity and its electric feed (Romex cable, etc.) has a ground wire (equipment grounding conductor).

J. V. 11-16-2011 11:02 AM

Okay. Lets start with the system grounding. If your house has metal water lines they must be grounded to the system ground at the main panel. The metal water line entering the dwelling must be in contact with at least 10' of earth. Which it will be if underground. This connection must/should be made within 5' of where the water line enters the dwelling.
Grounding of the gas lines is also required. These conductors (bare or insulated wires) must go to the main panel where the ground rod is located.
Sub panels are wired differently than main panels and since you have a total of 4 wires going to the sub, all you must do is check to see if it is wired correctly. (search forum for "sub panels'). You will find the information here that you need.
Now that you have installed a proper receptacle, the green wire can be disconnected from the metal pipe and discarded. You now have a proper ground that goes back to the panel. No extra grounding is required.

Article 100 of the NEC is where you find the definitions.

Bonded (Bonding). Connected to establish electrical continuity
and conductivity.

Ground. The earth.
Grounded (Grounding). Connected (connecting) to
ground or to a conductive body that extends the ground

So, make sure your system is properly grounded/bonded and make sure your sub panel is wired correctly.

John318 11-16-2011 11:14 AM

There is no basement. I live in Louisiana. The water meter is around 100' from the house itself in the ground. I can see no wire on either side of the meter, but I will dig around it a little further to see if I can locate one.

There is a wire that comes out of the ground right next to the gas line (practically wrapped around it as the line exits the ground). However, this wire goes up about a foot and isn't actually connected to the line. It is insulated, so there is no contact. I suppose the grounding of the actual furnace plug will act as bonding.

I am at a loss with the water pipes. They enter the house at the water heater and I can easily access them, but running a wire back to the main seems strange considering there is a sub panel 35" away. However, if it is not proper to bond at the sub, then I won't do it. I was hoping this was acceptable as it seemed better than no bond at all. The biggest pain is that the feed to the sub panel to the outer main panel is through a wall into the back of the panel. There is no entrance for a new wire unless I open the wall up. I just finished closing and finishing that very same hole!!

Why is it that every DYI project I choose always becomes a larger project mid stream? HaHa.

J. V. 11-16-2011 11:19 AM

Ground/bond at the accessible location. You do not need to run a wire all the way out to the meter. The water line in the ground coming to the house is a sufficient electrode in itself. You also have the gas lines and the ground rod or rods.
If we were building this house, we would take all these things into consideration. But this house is built. You can only do so much.

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