We provided an earthing system to a building to have an earth electrode resistance to earth of less than 10 Ohms using multiple earth electrodes(copper clad steel rods) forming a close grid/mesh.The main building (1) Receives a three phase,50 Hz, 400 V utility power supply from an overhead transmission line (2) connected to two overhead telephone lines and has a PABX exchange(3) supplied from a standby generator 400 V,50 Hz,100 kVA, but housed in a separate building 75 ft from the main building. Underground cables connect the generator and the main building(4) No building lightning protection system(5) A swimming pool is located equidistant from the main building and generator room (6) Surveillance cameras are fixed along the perimeter of the ground area which is about 250 ft x 250 ft. We use the TT system.
My question is – Could I interconnect to the earth grid the earth conductors of (1) Building power distribution system (2) Telephone System (3) Generator neutral point and frame (4) swimming pool structural steel (5) screen of the sensor cables of surveillance system (a) at closest points to each facility (b) at a single earth bus bar?
Thank you for your question regarding the bonding of various grounding systems, it is our pleasure to help.
Not only should you bond all of the grounding systems at your building together, but you MUST bond all of the systems together! The bonding of these systems is mandatory under every known regulation and standard world-wide.
The copper ground bar system is one of the best methods for bonding these systems together. In fact, there are some standards that actually have specific requirements for how to properly wire a ground bar. Basically, the idea is to have inputs at the top of the ground bar, and outputs at the bottom.
For your building, you would want to see the 10-ohm grounding electrode system brought in to the bottom of the ground bar, and then bonding conductors for all the other systems connected to the top of the ground bar. So you would see the building power distribution ground, the Telco ground, generator, swimming pool equipotential ground, the surveillance system ground, lightning protection ground, gas pipe ground, water pipe ground, computer server ground, and all other grounding systems bonded to the top of the ground bar. You may find that multiple ground bars are needed. Of course, all conductors bonded to the ground bar should be installed with double-bolt connections and be properly labeled.
The swimming pool equipotential grounding system and building steel, including the rebar in the concrete, is often considered to be part of the grounding electrode system, and is sometimes bonded to the bottom of the ground bar.
We recommend you take a look at Motorola’s R56 standard for some additional guidance. While it does not specifically relate to your situation, it does have some of the best illustrations and common-language instructions you will find anywhere.
If you have any additional questions, please do not hesitate to call us at 310-318-7151 California time, and someone will be more than happy to discuss your project with you free of charge.
The Engineering Team at E&S Grounding Solutions
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