Okay, let's analyze your proposed grounding scheme to see if it qualifies as a Ufer ground (concrete-encased electrode) according to NEC Article 250.52. Please describe or provide a diagram of your proposed grounding scheme.

General Requirements for Ufer Grounds (NEC 250.52(A)(3))

To qualify as a concrete-encased electrode (Ufer ground), the electrode must meet all of the following criteria:1.

Encased in Concrete

The electrode must be encased in at least 2 inches (50 mm) of concrete.2.

Location

The encasing concrete must be in direct contact with the earth.3.

Electrode Type and Size

The electrode must be one of the following: A bare or zinc-galvanized or other electrically conductive coated steel reinforcing bar or rod of not less than 1/2 inch (12.7 mm) in diameter and 20 feet (6.0 m) long. A bare copper conductor not smaller than 4 AWG and 20 feet (6.0 m) long.

Analysis Considerations Based on Your Description (Please provide specifics!)

Without a diagram or description of your grounding scheme, I'll have to make some assumptions and ask clarifying questions. Consider these points:

Is the Concrete Pad a Structural Component? This is very important. A Ufer ground is typically installed within the foundation of a building or structure. If your pad is simply a surface slab sitting on the ground, it might not be considered part of the "structure" and could be more problematic to classify as a Ufer. Electrode Placement

Where within the pad is the electrode located? Is it buried within the concrete, near the bottom of the pad, and meeting the 2-inch concrete cover requirement? Is it continuous for the full 20 feet, or are there breaks?

Electrode Material and Size

Are you using rebar or copper wire? What diameter/gauge is it? Is it the correct material (bare, galvanized, etc.)? Is it at least 20 feet long? If using rebar, is it continuous for the entire length? Are the rebar sections connected to each other?

Bonding

How is the electrode connected to the equipment inside the shipping container and the incoming 480V service? You will need a Grounding Electrode Conductor (GEC) from the Ufer ground to the grounding bus in the shipping container.

Ground Ring (If Applicable)

Are you planning on using a ground ring in addition to the Ufer? If so, how is the Ufer ground bonded to the ground ring? The NEC requires all grounding electrodes present to be bonded together.

Soil Conditions

While not part of the NEC definition of a Ufer, soil conditions around the pad can influence its effectiveness.

Common Problems and Considerations



Not Enough Concrete Cover

If the electrode is too close to the surface of the pad, it won't meet the 2-inch concrete cover requirement.

Insufficient Length

A 20-foot electrode is the minimum required length.

Improper Materials

Using the wrong type or size of electrode (e.g., insulated wire) will invalidate the Ufer ground.

Lack of Continuity (Rebar)

If using rebar, it's crucial to ensure electrical continuity throughout the 20-foot length, typically with overlaps and appropriate bonding (welding, clamps listed for grounding).

Pad Not Considered a Structure

If the concrete pad is not an integral part of the building or structure, some inspectors may be hesitant to accept it as a Ufer ground, even if it technically meets the requirements.

Resistance to Ground

Although not a requirement of a Ufer ground, the resistance to ground is a measure of grounding system quality. You want a low resistance value (typically 25 ohms or less, but often much lower). A Ufer ground usually provides a good, low-resistance connection.

Supplementation

250.53(A) states "A ground rod or pipe electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 6 ft (1.83 m) apart."

What to do Next


Provide a Detailed Description or Diagram

The more information you give me about your proposed grounding scheme, the better I can advise you. Include electrode type, size, placement within the pad, pad dimensions, and how it connects to the electrical system within the shipping container.2.

Consult with a Qualified Electrical Engineer or Inspector

This is the most important step.* An engineer or local electrical inspector can review your specific design and ensure it complies with the NEC and local codes. They can also assess the specific site conditions and make recommendations for the best grounding solution.3.

Consider Local Amendments

Local jurisdictions may have amendments to the NEC regarding grounding. Always check with your local authority having jurisdiction (AHJ).

In summary, whether your proposed grounding scheme qualifies as a Ufer ground depends entirely on the specific details of its construction. Providing a detailed description or a diagram will allow for a more accurate assessment. Flag for review