specifications - FAACO - Federal Aviation Administration Contract ...

FTWIC-2235June 2009H. Provide an Electronic Single Point Grounding System throughout the facilities inaccordance with this specification.1. The ELECTRONIC SINGLE POINT GROUND SYSTEM shall be isolated fromthe electronic multipoint ground system, power grounding system and thelightning protection system. The electronic single point ground system shall beterminated at the main ground plate or to the earth electrode system. Thenetwork shall be configured to minimize cable lengths. Conductive loops in thenetwork shall be avoided by maintaining a trunk and branch arrangement asshown on the drawings.2. GROUND PLATES: Main, branch and feeder ground plates shall be of copperand at least 6 inches long, 4 inches wide, and 1/4 inch thick. The plates shall bemounted on phenolic or other non-conductive material of sufficient cross sectionto rigidly support the plates after all cables are connected. Bolts or other devicesused to secure the plates in place shall be insulated or shall be of a nonconductingmaterial. The plates shall be mounted in a manner that providesready accessibility for future inspection and maintenance.3. ISOLATION: The minimum resistance between the electronic single pointground and the electronic multi-point ground systems shall be ten megohms. Theresistance shall be measured after the complete network is installed and beforeconnection to the earth electrode system or to the electronic multipoint groundsystem at the main ground plate.4. RESISTANCE: The maximum resistance between any ground plate and anycable connected to the plate shall not be greater than one milliohm.5. MAIN GROUND CABLE shall be an insulated 500 KCMIL cable from the mainground plate to the main single point ground plate. The cable shall be enclosedin PVC conduit in floor trenches or behind permanent structural members.6. TRUNK GROUND CABLES: An insulated trunk ground cable shall be installedin each facility from the main ground plate to each of the branch plates as shownon the drawings. This cable shall be 4/0 for lengths up to 400 feet. For longerruns, select a cable size based on providing a cross-sectional area of 500 KCMILper running foot of cable length. Trunk ground cables shall be bolted to theground plates directly with no washers separating them. The cable shall beenclosed in PVC conduit in floor trenches or behind permanent structuralmembers.7. BRANCH GROUND CABLES: Insulated copper branch ground cables shall beinstalled between feeder and branch ground plates. These cables shall be routedto provide the shortest practical path. Branch ground cables shall be No. 2 AWGfor lengths less than 75 feet and 1/0 AWG for lengths between 75 feet and 150feet. A No. 4/0 AWG cable shall be used for lengths greater than 150 feet.Branch ground cables shall be bolted to the feeder and branch ground plates. Thecable shall be enclosed in PVC conduit in floor trenches or behind permanentstructural members.16450-3