Okay, let's break down the discrepancy you're observing between the NEC handbook illustration and the typical installation you see in NYC electrical rooms regarding ground rods.

Understanding the NEC's Position NEC 250.68(A) Enclosures for Grounding Connections is the section you're looking for. It allows for the grounding electrode conductor to be run to a terminal bar or bus located in a suitable enclosure. The grounding electrode conductor must be connected to the grounding electrode in accordance with 250.64.

Why the Difference?

The NEC handbook image depicts the ideal grounding scenario for maximum effectiveness, as it shows the entire ground rod fully buried. However, practical considerations and local requirements often lead to modifications in the field. Here are the likely reasons for the observed differences in NYC:1. Inspection and Maintenance

Having a portion of the ground rod and the clamp accessible above the slab greatly simplifies inspection and maintenance. Inspectors can visually verify the connection is intact, not corroded, and properly sized without having to excavate or destroy the slab.2.

Testing

Being able to access the ground rod and clamp makes it possible to test the grounding electrode system with an earth ground resistance tester. This is important for verifying the effectiveness of the grounding system over time.3.

Mechanical Protection

While being encased in concrete provides some protection, the protruding section of the ground rod and the clamp are susceptible to physical damage in a busy electrical room if not installed correctly.4.

NYC Local Codes and Amendments

It's entirely possible that NYC's local electrical codes (which are based on the NEC but can include amendments) have specific requirements or preferences for grounding electrode accessibility. This is common in major cities.

This is the most likely reason for the observed practice.How Many Inches Above the Slab? The NEC does not specify a precise height above the slab. It generally focuses on ensuring a secure, protected, accessible, and testable connection. The height above the slab is usually determined by: Local practices

The prevailing installation method followed by electricians in the area, especially if based on local code interpretations.

Inspector preference

Some inspectors might have specific expectations for accessibility.

Manufacturer instructions

Instructions included with the ground rod clamp may specify clearances or installation methods.In practice, you'll typically see anywhere from

3 to 6 inches of the ground rod and clamp exposed above the slab. This provides enough room for visual inspection, cleaning, and testing, while minimizing the risk of accidental contact or damage.

Where to Find Answers?1. NYC Electrical Code

Review the NYC Electrical Code for any local amendments or requirements related to grounding electrodes. The NYC Department of Buildings website is the place to start.2.

Consult with Local Electrical Inspectors

The most definitive answer will come from the local electrical inspectors who enforce the code. They can explain their expectations for grounding electrode installations.3.

Experienced Local Electricians

Talk to experienced electricians who work in NYC commercial buildings. They will be familiar with the local practices and any specific requirements they encounter.

In Conclusion

While the NEC handbook shows a fully buried ground rod, the reality in NYC electrical rooms is different due to practical considerations, inspection needs, and potential local code variations. The specific height of the exposed ground rod above the slab isn't dictated by the NEC but is determined by local practice, inspector preference, and the need for accessibility for inspection and testing.

Always check local codes and consult with local authorities for the most accurate and up-to-date requirements. Flag for review