Multiple Underground Water Pipes

[wwhitney]

Note the language in 250.52(A)(1) "electrically continuous ... to the points of connection of the GEC", and how the sentence structure implies that's all part of the electrode.

I don't agree. The electrode is the "metal underground water pipe" meeting certain conditions. If the intention were "water pipe of which at least 10 ft is underground" that would have been the wording.

Also, there are other cases of extending an electrode for a connection. E.g. stubbing up rebar out of a concrete-encased-electrode to connect the GEC to.

Now consider whether anything in the 5ft rule language directly contradicts this implication.

The logic seems pretty clear to me: whatever the extent of the electrode is, we could connect our GEC to anywhere along that extent. So portions of the water pipe to which we are prohibited from connecting our GEC, like more than 5 ft to the interior of the building (barring the exception), must not be part of the electrode.

Cheers, Wayne

 

[Dennis Alwon]

Not so much a what if scenario as arguing that the electrode definitely does not extend more that 5' inside the building. So if the electrode for one section of underground pipe does not overlap with the electrode for another underground section, you have two electrodes.

Let me flip this around: suppose I managed to get a 25' ground rod, and I bent it into a U shape with two 9' vertical segments and a 7' horizontal segment, and I drive/bury it so that both vertical segments are at least 8' in the ground. Does that count as two ground rods, or just one? Seems like it is obviously two.

So likewise, if you have two separate underground water pipe segments (separated by >10' of interior water piping) you have two separate electrodes.

Cheers, Wayne

Sure there are 2 ground rods and there are 2 electrodes but there is no need for a bonding jumper since both are already connected together. I thought your original point was that there were 2 electrodes and each had to be connected to a grounding electrode conductor. One connection is all that is needed, imo

 

[Fred B]

250.68 (C) Grounding Electrode Conductor Connections.
Grounding electrode conductors and bonding jumpers shall be permitted to be connected at the following locations and used to extend the connection to an electrode(s):
(1) Interior metal water piping that is electrically continuous with a metal underground water pipe electrode and is located not more than 1.52 m (5 ft) from the point of entrance to the building, as measured along the water piping, shall be permitted to extend the connection to an electrode(s). Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building, as measured along the water piping, shall not be used as a conductor to interconnect electrodes of the grounding electrode system.

 

[Fred B]

There seems to be in the discussion an intermixing of reference of differing GE's. A water pipe electrode and a pipe electrode are not one in the same. An underground Water pipe electrode (250.52(A)(1)) is considered separately from a "pipe" electrode (250.52(A)(5)) in the codes. A "pipe" electrode is included with a rod electrode and it's requirements in the code.
2 water pipes (or even more) does not constitute a GES on it's own, it must be supplemented by another electrode of a different type (250.53(D)(2)). A water pipe also does not have a 25 ohm allowance for sole use as an electrode.

 

[Dennis Alwon]

There seems to be in the discussion an intermixing of reference of differing GE's. A water pipe electrode and a pipe electrode are not one in the same. An underground Water pipe electrode (250.52(A)(1)) is considered separately from a "pipe" electrode (250.52(A)(5)) in the codes. A "pipe" electrode is included with a rod electrode and it's requirements in the code.
2 water pipes (or even more) does not constitute a GES on it's own, it must be supplemented by another electrode of a different type (250.53(D)(2)). A water pipe also does not have a 25 ohm allowance for sole use as an electrode.

I believe the code considers the replacement of water pipes in the future with plastic pipes, thus the need for the ground rods.

 

[wwhitney]

I thought your original point was that there were 2 electrodes and each had to be connected to a grounding electrode conductor.

Yes.

One connection is all that is needed, imo

I don't see how that can be true given 250.68(C)(1), the interior metal water piping after 5' can't be used to interconnect electrodes.

Cheers, Wayne

 

[Dennis Alwon]

Yes.

I don't see how that can be true given 250.68(C)(1), the interior metal water piping after 5' can't be used to interconnect electrodes.

Cheers, Wayne

You make a good argument there. I have nothing I can add that will answer this issue. I suppose it would need another grounding electrode conductor.

 

[Fred B]

So likewise, if you have two separate underground water pipe segments (separated by >10' of interior water piping) you have two separate electrodes.

Yes and no. It meets the 10 ft rule but with a water pipe, it only counts as one Grounding Electrode for code rules. It cannot be left without additional GE's being added and even achieving 25 ohms doesn't let it be a solo GE. If such installation was a pipe electrode not a water pipe it would be the same as a ground rod, and your scenario would be valid.

Maybe someone can explain how adding water into the pipe changes its application other than the code's wording.

 

[wwhitney]

Yes and no. It meets the 10 ft rule but with a water pipe, it only counts as one Grounding Electrode for code rules.

What section of the NEC says that?

I certainly agree with your point that a GES consisting of multiple underground water pipe electrodes still needs a supplemental electrode. But if a continuous metal water pipe, with two underground sections separated by more than 10' of interior water piping, is two electrodes, then it needs two GECs, one going to each electrode, each connected within 5' to the interior of the particular underground segment.

Note that 250.52(A)(2) on "Metal In-Ground Support Structures" and 250.52(A)(3) on "Concrete-Encased Electrodes" both specify that if multiple electrodes of the respective type are present, only one requires connecting to the GES. 250.52(A)(1) on "Metal Underground Water Pipes" does not have that language. So each of the 250.52(A)(1) electrodes needs to be connected to the GES.

Cheers, Wayne