Water Pipe Bond

[shortcircuit2]

According to the 2017 NEC, section 250.104(A), what size AWG copper interior water pipe bond is needed for a 1600-amp service fed with 4 x 600mcm copper parallel ungrounded supply conductors?

 

[infinity]

Multiply 4*600=2400, size for 2400 kcmil.

 

[shortcircuit2]

So 12 1/2% of 2400?

 

[infinity]

Read note#1 of T250.102(C)(1) and the section after the asterisk at the bottom.

 

[shortcircuit2]

OK...so i read that and don't get any additional guidance from it.

So I multiply 2400mcm by 12.5% and get 300mcm?

What am I missing?

 

[don_resqcapt19]

It appears that the * note comment is in conflict with the actual code text in 250.104(A)(1), which says "...shall be sized in accordance with Table 250.104(C)(1). The * note says the table does not apply to the water pipe bonding jumper as it is not one of the items noted. It is my opinion that the 12.5% rule does apply to the water pipe bonding jumper.

 

[shortcircuit2]

OK...thanks Don...I thought I was missing something.

 

[infinity]

It appears that the * note comment is in conflict with the actual code text in 250.104(A)(1), which says "...shall be sized in accordance with Table 250.104(C)(1). The * note says the table does not apply to the water pipe bonding jumper as it is not one of the items noted. It is my opinion that the 12.5% rule does apply to the water pipe bonding jumper.

I agree, the way that it's written it is incorrect to even use this table since it's not on the list of bonding jumpers types that apply to this table. IMO 250.104(A) should reference Table 250.66 because if the water pipe qualifies as a GEC then #3/0 is the largest GEC required. Why would a bonding jumper need to be larger than the largest GEC required for a water piping system?

 

[shortcircuit2]

Why would a bonding jumper need to be larger than the largest GEC required for a water piping system?

Yes...this is the other part I have been confused about.

1. If the street water pipe is a qualifying electrode for the 1600-amp service with 4x600mcm...250.66 calls for a 3/0 copper GEC. But my interior water pipe bond needs to be 300mcm???

2. If the street water pipe into the building is plastic...then I just bond the metal interior water pipe with 300mcm???

Guess this section needs some clean up.

 

[infinity]

Yes...this is the other part I have been confused about.

1. If the street water pipe is a qualifying electrode for the 1600-amp service with 4x600mcm...250.66 calls for a 3/0 copper GEC. But my interior water pipe bond needs to be 300mcm???

2. If the street water pipe into the building is plastic...then I just bond the metal interior water pipe with 300mcm???

Guess this section needs some clean up.

As Don pointed out this seems to be an error in the NEC that probably resulted from them making a separate table for bonding jumpers. Since they say explicitly that this does not apply to the conductor bonding a water piping system then water piping systems should be bonded according to T250.66 just like a water pipe electrode. If it were me I would use a #3/0.

 

[shortcircuit2]

OK...right....thanks for the feedback on this. You have probably discussed this here before already but I didn't find any thread on this in a search.

In the 2014 NEC they have it right with the reference to T250.66.

There was a change in 2017 to T250.122(C)(1) that creates the conflict discussed here.

There are no TIA's on this or errata that I could find.

There is 1 public input (3203) to go back to T250.66 in 2020

Hopefully CMP 5 will fix this for 2020.

 

[don_resqcapt19]

I agree, the way that it's written it is incorrect to even use this table since it's not on the list of bonding jumpers types that apply to this table. IMO 250.104(A) should reference Table 250.66 because if the water pipe qualifies as a GEC then #3/0 is the largest GEC required. Why would a bonding jumper need to be larger than the largest GEC required for a water piping system?

But the only reason for the addition of Table 250.104(C)(1) was so Table 250.66 would be used only for the grounding electrode conductor.

As far as the sizing, the water pipe bond may be part of the fault clearing path, however it is my opinion that the water piping bonding conductor should be sized based on the largest service OCPD and Table 250.122.

 

[infinity]

But the only reason for the addition of Table 250.104(C)(1) was so Table 250.66 would be used only for the grounding electrode conductor.

As far as the sizing, the water pipe bond may be part of the fault clearing path, however it is my opinion that the water piping bonding conductor should be sized based on the largest service OCPD and Table 250.122.

Prior to this inclusion of this new table it was sized according to 250.66 and not required to be larger than #3/0. I see no reason why it should need to be larger than a GEC connected to a water pipe that qualifies as a grounding electrode. I would guess that the intention of the CMP was not to suddenly require a water pipe bonding jumper to be larger than was required by previous code editions.

 

[don_resqcapt19]

Prior to this inclusion of this new table it was sized according to 250.66 and not required to be larger than #3/0. I see no reason why it should need to be larger than a GEC connected to a water pipe that qualifies as a grounding electrode. I would guess that the intention of the CMP was not to suddenly require a water pipe bonding jumper to be larger than was required by previous code editions.

There is a PI for the 2020 code that would return the water piping bonding jumper sizing to Table 250.66. The following is the substantiation for that PI.

My understanding is that this change was made by the technical correlating committee and that it was not a panel 5 initiated change. This PI is so that panel 5 can discuss it and determine what the intention was. It appears, to the author of this PI, that the correct reference is T250.66, as this retains alignment with the rest of the Article.

The new table was in the 2014 code, but the water pipe bond still referenced Table 250.66.