Mike Dolt Enterprises
Mike Dolt Enterprises
User: Tulsa Electrician, Location: Tulsa
Asked on: Sunday, April 6, 2025 at 11:29 am EDT
Answered on: Sunday, April 6, 2025 at 11:29 am EDT
Question: There is four services on a single building.As part of the GES the four service all have a 3/0 GEC to the CEE.The water service is plastic.There is two rod electrodes driven at each service.The metal part of the building has steel columns. (1 service)The rest of the building is wood framed where the other services are located. (3 services)From one service they have a GEC ran to building steel. The only tie to all four is the CEE.Question:Since the CEE is the only tie ( common) to the four and only one has a GEC to the steel. Would the CEE common be considered a violation under 250.53 (C) 2020 NEC.
Let's break this down according to the 2020 NEC, focusing on 250.53(C) and relevant grounding electrode system requirements.
Understanding 250.53(C) - Supplemental Electrode Required
This section essentially says that if you're using a concrete-encased electrode (CEE) and it's not supplemented by at least one additional electrode of a type specified in 250.52(A)(2) through (A)(8), you might have issues. In your case, the supplementary electrodes are rod electrodes and the metal column of the building.
Analysis of Your Situation
Four Services with CEE
Each of the four services has a 3/0 AWG grounding electrode conductor (GEC) connected to the CEE. That's a good start.
Two Rod Electrodes at Each Service
Each service has two rod electrodes. This, along with the CEE, meets the requirement of having a supplementary electrode (250.52(A)(5)).
Water Service is Plastic
Since the water service is plastic, you can't use it as a grounding electrode (250.52(A)(1)).
Building Steel (One Service)
One service has a GEC connected to the building steel. This is a good practice, especially since it inherently helps to bond the metal building frame to the electrical system.
The Question of Violation
The core question is whether the CEE being the sole common connection point and only one service having a GEC to the steel constitutes a violation of 250.53(C) or other grounding requirements.
250.53(C) and Supplementary Electrodes are being met
Each service has the required supplemental rod electrodes installed for the CEE. Therefore the requirement is being met.
Building Steel Connection
The fact that only one service has a direct connection to the building steel is the problematic area of the installation.
Conclusion
The described installation may be non-compliant because of the building steel only being grounded by a single service. While each service has a CEE and supplemental rods, the building steel is only tied to one service.
Recommendations
A qualified electrical inspector should be consulted to determine the precise interpretation and application of the NEC to your specific installation. Flag for review