Sizing Ground for New Ladder Tray with DC Conductors

3/0 seems to be the max size....

250.166 Size of the Direct-Current Grounding Electrode Conductor

The size of the grounding electrode conductor for a dc system shall be as specified in 250.166(A) and (B), except as permitted by 250.166(C) through (E). The grounding electrode conductor for a dc system shall meet the sizing requirements in this section but shall not be required to be larger than 3/0 copper or 250 kcmil aluminum or copper-clad aluminum.

(A) Not Smaller Than the Neutral Conductor

If the dc system consists of a 3-wire balancer set or a balancer winding with overcurrent protection as provided in 445.12(D), the grounding electrode conductor shall not be smaller than the neutral conductor and not smaller than 8 AWG copper or 6 AWG aluminum or copper-clad aluminum.

(B) Not Smaller Than the Largest Conductor

If the dc system is other than as in 250.166(A), the grounding electrode conductor shall not be smaller than the largest conductor supplied by the system and not smaller than 8 AWG copper or 6 AWG aluminum or copper-clad aluminum.

(C) Connected to Rod, Pipe, or Plate Electrodes

If connected to rod, pipe, or plate electrodes as in 250.52(A)(5) or (A)(7), that portion of the grounding electrode conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum or copper-clad aluminum wire.

https://up.codes/viewer/texas/nfpa-70-2023/chapter/2/wiring-and-protection#250.146_%28D%29

The NEC is unlikely to offer any guidance on noise reduction capability of grounding conductors.

The engineering solution for this involves calculating the absolute maximum ground fault current available, the highest probable fraction of that current through the conductor, the sensitivity of the ground fault protective equipment, the maximum time the backup or secondary protection for any circuit will stay on, and the short term heating curve for the conductors and connection systems. Also take into account the minimum current and voltage necessary to sustain an arc that is unlikely to be self extinguishing.

The use of a fits-all code written for typical installations with a basis in previous loss prevention is little comfort when your installation fails and results in significant damage, or you have spent a significant premium of time and material on measures that may yet prove to be inadequate.

Oh, and I left off a couple more things, investigate and design for future corrosion damage due to galvanic action, where dissimilar metals are bonded, and account for conductor stresses at installation time, where a lesser gauge conductor or stranding design may be damaged during normal installation and/or handling techniques.

It seems the code is saying that the ground conductor not be smaller than...

In the radio business where noise is a concern, the bigger the ground the better. This is true for the transmision system as well as the case grounding system. A larger and more efficient ground system is a major factor in the quality of the signals broadcast ie lower noise floor, as well as the range of the broadcast signal ie better ground wave conduction.

An example of range limitation due to loss of grounding is a CHP station in the sierra foothills lost it's range when the ground around the tower was paved for parking and lost the moisture around the grounding rods at the base of the tower over time. The signal lost range by several miles and formed shadow pockets in the valleys in the area where the cars would lose signal. even bumping the transmission power wouldn't bring it back.

In short, when talking about grounding, it is my opinion that bigger is always better. I don't see that the code disagrees.

Duplicate topic.