main grounding electrode

[butter]

Gentlemen,

I have 2 questions I'd like help with please.


1. When multiple grounding electrodes are available ( water pipe, ground rod, building steel etc), how do you determine which is the main grounding electrode and which are supplemental electrodes even though they required to be bonded together?

2. And suppose a natural gas piping system is available and required to be BONDED and Grounded what keeps it from being the main grounding electrode particularly if it's ground resistance is lower than the other available grounding electrodes?

Bob

 

[Dennis Alwon]

Gentlemen,

I have 2 questions I'd like help with please.


1. When multiple grounding electrodes are available ( water pipe, ground rod, building steel etc), how do you determine which is the main grounding electrode and which are supplemental electrodes even though they required to be bonded together?

Pick one-- if you choose the rod then you need to size the conductor as large as is req. for the other. Generally I use the water pipe if it is an electrode. Sometimes the building steel does not qualify as an electrode

2. And suppose a natural gas piping system is available and required to be BONDED and Grounded what keeps it from being the main grounding electrode particularly if it's ground resistance is lower than the other available grounding electrodes?

Bob

The gas meters generally have a dielectric fitting so that would not make it an electrode. Generally the bonding of the gas pipe is done automaticall with the equipment grounding conductor of the circuit feeding a gas appliance.

 

[Dennis Alwon]

Btw, art.250.104(B) is for the gas bonding

250.104(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 any of the following:
(1) Equipment grounding conductor for the circuit that is
likely to energize the piping system
(2) Service equipment enclosure
(3) Grounded conductor at the service
(4) Grounding electrode conductor, if of sufficient size
(5) 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 points of
attachment of the bonding jumper(s) shall be accessible.

 

[mwm1752]

Not sure there is a main electrode just an electrode system -- all have specific GEC sizing and you shall use all of the ones for the structure -- If there was one I would say concrete encased UFUR

 

[Smart $]

Pick one-- if you choose the rod then you need to size the conductor as large as is req. for the other. Generally I use the water pipe if it is an electrode. Sometimes the building steel does not qualify as an electrode.

...

Agree.

I generally choose the one likely to have the best earth grounding capacity. Typical preference: 1) CEE, especially continuous tie-wired rebar throughout footer, 2) ground ring, 3) qualifying structural steel 3) water pipe, second to last when previous exist, and 5) rod, pipe, or plate electrode.

CEE can change in the order if it barely meets the criteria. Water pipe can change in the order dependent on being metal all the way to a community metal supply (if known).

Underground gas pipe may qualify if you catch it on the supply-side of the dielectric union. I'd put it in the same category as a water pipe.

 

[mwm1752]

Underground gas pipe may qualify if you catch it on the supply-side of the dielectric union. I'd put it in the same category as a water pipe.[/QUOTE]


250,52(B) never use underground metal gas piping as an electrode :happysad:

 

[Smart $]

250,52(B) never use underground metal gas piping as an electrode :happysad:

It was an errant thought which I do have from time to time. I was reading 250.52(A)(8) and didn't read 250.52(B).

Thanks for exposing and quashing. :happyyes:

 

[infinity]

According to the NEC there is no such thing as a main electrode.