House configuration: 1950s California ranch style single story with attic. Late 1960s split bus panel with probably 100A service. 120V outlets in house are ungrounded 2-prong. Gas enters house adjacent to electrical panel. Underground copper water service enters house around on other side, near hot water heater.
Grounding electrode system: 3x 8' copper clad rods driven into earth and linked by 4 gauge bare copper wire continuing to panel. This grounding system is currently NOT bonded to the nearby gas entry to the house. Once entering wall, the black steel gas pipe runs up and across the attic before descending to gas water heater. At that gas water heater, the gas pipe and adjacent copper cold and hot water pipes are bonded to each other with large bare copper wire (4 or 6 gauge), but not to anything else.
Question: Would bonding the gas pipe at its entry to house to the grounding electrode conductor nearby electrically join the grounding electrodes/conductor, the black steel in-house above-ground gas piping, and the copper water pipes into a single grounding system?
- Clearly, the grounding electrodes and conductor ARE part of the system.
- The 2020 Minnesota EC 250.50 (I couldn't find the general US one) states:
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system.
(1) Metal Underground Water Pipe A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductor(s) or jumper(s), if installed.
Our water pipe is in direct contact with the earth for probably 20 feet underground from the house to the streetside meter. It is bonded to the black steel gas pipe. Shouldn't the black steel gas pipe serve to make it "electrically continuous" to a bonding jumper from the gas pipe entry to the grounding electrode conductor?
Edit: As prompted by the excellent comment of mannaseh... it was code section 250.130(C) of the 2020 Minnesota NEC that prompted my thought:
(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions
The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system as described in 250.50
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates
(4) An equipment grounding conductor that is part of another branch circuit that originates from the enclosure where the branch circuit for the receptacle or branch circuit originates
(5) For grounded systems, the grounded service conductor within the service equipment enclosure
(6) For ungrounded systems, the grounding terminal bar within the service equipment enclosure
To me, it seems (C)(1) applies, as the 250.50 description of the grounding system includes all of the possible electrodes when bonded together.
Note: I am not trying to use underground gas pipe as a grounding electrode, but rather the above-ground in-house black steel gas piping to electrically connect our main grounding electrodes and conductor with the copper water pipe system on the other side of the house. As there is currently no electrical ground running to the finished/water pipe containing 2/3 of the house, it would be very convenient to begin incremental addition of grounds to outlets by bonding to nearby copper water pipe before eventually connecting a "real" ground from the other side of the house.
Results edit: It seems clear that no matter the physical properties of the gas pipe, it is not an approved wiring method, and so I will just have to run a bond to the gas pipe by its entry for its own reason, and run a proper ground out to the currently ungrounded house outlets. I very much appreciate the comments and discussion here.