Mike Dolt Enterprises
Mike Dolt Enterprises
User: clavila, Location: Florida
Asked on: Thursday, April 28, 2011 at 11:15 am EDT
Answered on: Tuesday, May 14, 2024 at 4:44 am EDT
Question: I have a cellular tower site with 5 meters, 1 for local service (lighting) and 4 for future operators.I have a 50 kva transformer in a pole at the front of the property where the meters are located and the tower site is about 100 yards away.I have to ground at the meter location according to the POCO and besides the transformer is grounded as well. At the tower we have a complete grounding system designed for the lightning arresters. Less than 1 ohm. There is a structure at the tower site for a main breaker for each of the 5 services.I bond the neutral to the ground electrode at the meters but do I install 4 cables for each service and keep the neutral isolated at the tower site? Or may I just install three cables and reconnect the neutral to ground at the tower site.Is there a matter of grounding conductor length that allows me to do this?Best regards to all
Grounding Requirements at the Tower Site
According to the National Electrical Code (NEC) and industry best practices, the following grounding requirements apply: The neutral conductor cannot be grounded at multiple locations within the electrical system. All services at the tower site must be grounded at the same point.
Grounding Options
Based on these requirements, you have two main options
Option 1: Separate Grounding Conductors
Install four separate grounding conductors from the meter location to the tower site, one for each service. Maintain isolation of the neutral conductors throughout the system, all the way to the tower site. Connect each grounding conductor to the grounding electrode system at the tower site.
Option 2: Shared Grounding Conductor Install three grounding conductors from the meter location to the tower site, omitting the neutral conductor. Connect the grounding conductors to the grounding electrode system at the tower site. Reconnect the neutral conductor to ground at the tower site.
Grounding Conductor Length
The NEC does not impose a specific limit on the length of grounding conductors. However, good engineering practice suggests keeping the length of grounding conductors as short as possible to minimize resistance.
Recommendation
Based on the requirements and options described above, it is recommended to use Option 1: Separate Grounding Conductors. This ensures proper grounding and isolation of each service, and minimizes the potential for electrical hazards.
Additional Notes The grounding electrode system at the tower site should be designed to maintain a resistance of less than 1 ohm. The grounding conductors should be sized appropriately for the fault current levels at the tower site.* It is also advisable to install surge suppressors at the tower site to protect against lightning strikes. Flag for review