Home Improvement Asked by Scott Taylor on October 19, 2020
The backstory:
My HVAC friend, my dad and myself installed new gas pipes in my house after the 40 y/o pipe started leaking. Suffice to say, the old pipe was beyond repair, every retightening of the pipe resulted in the next elbow becoming lose to the point, I would be tearing out drywall, air ducts and possibly beams to access it. So we ran new pipe.
We got the permit, had the county do the inspection. It passed, and we had Xcel (electric and gas utilities) come out and replaced the meter which was also old and leaking, and turn on the gas.
The setup passed inspection with a larger than needed ground wire going from the black pipe, near the meter, to a grounding pole going 5 feet underground. Xcel comes out today to replace the meter and hook up the gas and says my grounding wire cannot be there, that it will ruin the meter and rust the pipe where the wire clamps to the pipe and that a small current runs from my appliances to the meter. There is about 9 combined feet of pipe exposed outside, from the meter to where the pipe enters the house. I asked, what if lightning strikes the pipe and the Xcel guy says “Lightning will hit another part of the house first.” So I call my HVAC, ask his opinion, I talk to a retired Master PLumber at Home Depot, and the county Fire Marshall and they all agree that it should be grounded. Oddly enough the Fire Marshall comments, “even if lightning hits the pipe, nothing will happen”.
Remember, this is a black iron pipe installation, not CGGT. It is black iron pipe all the way from the meter to the room with the water heater and furnace. From the black pipe, a yellow flex pipe goes to the water heater, and a stainless steel flex pipe goes to the furnace.
So the plumbers and county is saying something different than Xcel. Should the pipe be grounded? Is bonding at the furnace enough?
Can I put a thin layer of something between the clamp and the black pipe? Foam, thin plastic, wax paper? The Fire Marshall suggested dirt ?!?
According to National Electrical Code, the pipe has to be bonded. However, it can be bonded using the grounding conductor serving the equipment that uses the gas.
...The equipment grounding conductor for the circuit that is likely to energize the piping shall be permitted to serve as the bonding means...
As for lightning strikes, the gas company is probably correct. It's not likely lightning will strike the pipe, especially since it's right next to a house.
National Electrical Code 2014
Chapter 2 Wiring and Protection
Article 250 Grounding and Bonding
250.104 Bonding of Piping Systems and Exposed Structural Steel.
(B) Other Metal Piping. If installed in, or attached to, a building or structure, a metal piping system(s), including gas piping, that is likely to become energized shall be bonded to the service equipment enclosure; the grounded conductor at the service; the grounding electrode conductor, if of sufficient size; or to one or more grounding electrodes used. The bonding conductor(s) or jumper(s) shall be sized in accordance with 250.122, using the rating of the circuit that is likely to energize the piping system(s). The equipment grounding conductor for the circuit that is likely to energize the piping shall be permitted to serve as the bonding means. The points of attachment of the bonding jumper(s) shall be accessible.
Answered by Tester101 on October 19, 2020
Always bond everything metalic to the common ground
Answered by wireman on October 19, 2020
The issue of accelerated corrosion is true. Current can flow from the electrical system through the gas pipe, through the meter and outside. This can cause corrosion due to any different metals used between the two systems, and due to current flow.
It's also true that you have to ground your gas pipe according to the NEC. Even if you did what the gas company employee said and disconnect the ground wire, any stove or gas dryer is going to connect the metal parts of the appliance to both the electrical ground wire, and the metal gas pipe.
So how do you solve these two problem? Generally this is solved through the gas piping in your house being connected to the meter via a dielectric union. The dielectric union connects two sets of pipes together, but electrically isolates one from another by an insulator. It protects against both "stray current", and any corrosion due to a galvanic reaction between dis-similar metals.
I'm not sure why the XCEL employee didn't know about this.
Answered by Steve Sether on October 19, 2020
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