Ground rods conductor sizing

[hhsting]

Attached sketch two scenarios all following the NEC 2014 Article 250.64(D)(1),(2) or (3).

Scenario #2 shows tapped grounding electrode conductor (GEC) label #2 from each service disconnect to ground busbar. From the ground busbar their is common grounding electrode conductor label #2 go to ground rods per NEC 2014 Artocle 250.64(D)(3). Between ground rod their is also conductor #1 connecting the rods as shown in sketch.

Scenario #1 their is GEC labeled #2 from neutral bar in service trough to building steel and from steel their is bonding jumper to ground rods. Between ground rod their is also conductor #1 connecting the rods as shown in sketch.

Following questions:

1. Scenario #2 conductors #2 and #1 common grounding electrode conductor which code section would determine their size? #6 Awg is ok or size per Table 250.66 greater than #6 awg?

2. Scenario #1 conductors #2 and #1 bonding jumper which code section would determine their size? #6 Awg or size per Table 250.66 greater than #6 awg?

3. If the ground busbar is in the service trough would that be considered accessible per NEC 2014 Article 250.64(D)(1) or it would not be consider accessible?


Please all reference NEC 2014

 

[tom baker]

GEC to ground rod or rods not rewuired to be larger than 6 awg.
you quoting table 250.66 incorrectly, its section 250.66, A, B, or C.
Not sure on your trough question, but installing a ground bar in the trough would be difficult to make up connections and bonding of gecs

 

[david]

IMO the service entrance conductors connect directly to the utility and end in your through shown below the service disconnects

In your sketch I’m not seeing a common grounding electrode conductor

Conductor # 1 is a bond to grounding electrode #2

Conductor #2 Is the sole portion of the bond from the allowed busbar in 250.64 (F) (3)
Not 250 .64 (D) (1) (3) { which is a allowed tap method “busbar” to connect a common grounding electrode to “grounding electrode taps” from your ganged service disconnects}

The busbar found in 250.64 (D) (1) (3) and the busbar found in 250.64 (F) (3) serve two different purposes.

To be more correct you would run a common grounding electrode conductor to the busbar allowed in 250.64 (F) (3)

Or an a grounding electrode conductor from the trough below your two service disconnects


Edit: as Tom Mentioned the portion used as the sole connection to ground rods not required larger than #6

 

[hhsting]

I am having hard time figuring out which part is a GEC that is sole connection to ground rods. In Scenario #1 conductor #1 or #2 and Scenario #2 conductor #1 or #2 are they GEC or common GEC or bonding jumper?

 

[kwired]

either method you show is acceptable. Conductor that is sole connection to rod and pipe electrodes never needs to be larger than 6 AWG copper. Conductor that is sole connection to a CEE never needs to be larger than 4 AWG copper. Conductors to water pipes and building steel need to be sized per the table in accordance to the service conductor size.

 

[david]

I am having hard time figuring out which part is a GEC that is sole connection to ground rods. In Scenario #1 conductor #1 or #2 and Scenario #2 conductor #1 or #2 are they GEC or common GEC or bonding jumper?

You do not have a common grounding electrode conductor in either of your two designs.

Because you are using a busbar allowed in 250.64 (F) (3) the grounding electrode conductors are the conductors between the two service disconnects that land on the busbar.

The other conductors are grounding electrode bonding jumpers.

The conductors in question to the ground rods are bonding jumpers

Since the bonding jumper from the busbar to the first ground rod is solely for ground rods it is not required to be larger than 6awg. The bonding jumper to the second ground rod is also not required to be larger than 6awg

If instead you bonded the ground rod to a CEE requiring a #4 grounding electrode conductorthe bond from the busbar to the first ground rod would no longer be solely for ground rods, the bond from the busbar to the first ground rod would have to become a #4 bonding jumper.

The bond from the first ground rod to the CEE would also become a # 4 bonding jumper

If you bonded from the busbar to the first ground rod and bonded from the first ground rod to a CEE and also bonded from the first ground to a second ground rod than only the bond from the first ground rod to the second ground rod would solely be for a ground rod, only that bond from first rod to the secound would be allowed to be a #6 awg

 

[hhsting]

Attached sketch two scenarios all following the NEC 2014 Article 250.64(D)(1),(2) or (3).

Scenario #2 shows tapped grounding electrode conductor (GEC) label #2 from each service disconnect to ground busbar. From the ground busbar their is common grounding electrode conductor label #2 go to ground rods per NEC 2014 Artocle 250.64(D)(3). Between ground rod their is also conductor #1 connecting the rods as shown in sketch.

Scenario #1 their is GEC labeled #2 from neutral bar in service trough to building steel and from steel their is bonding jumper to ground rods. Between ground rod their is also conductor #1 connecting the rods as shown in sketch.

Following questions:

1. Scenario #2 conductors #2 and #1 common grounding electrode conductor which code section would determine their size? #6 Awg is ok or size per Table 250.66 greater than #6 awg?

2. Scenario #1 conductors #2 and #1 bonding jumper which code section would determine their size? #6 Awg or size per Table 250.66 greater than #6 awg?

3. If the ground busbar is in the service trough would that be considered accessible per NEC 2014 Article 250.64(D)(1) or it would not be consider accessible?


Please all reference NEC 2014

Does anyone know question #3?

 

[roger]

Does anyone know question #3?

What do you think?

Roger