GROUNDING AND LIGHTNING PROTECTION
620-1 Description.
Furnish and install grounding and lightning protection to provide personnel and equipment protection against faults, surge currents and lightning transients. Provide a grounding and lightning protection system in accordance with the details shown in the Standard Plans unless otherwise shown in the Plans.
620-2 Materials.
620-2.1 Ground Rods: Use ground rods meeting the requirements of UL 467 that are
listed by an OSHA Nationally Recognized Testing Laboratory (NRTL). Ground rods must be made of copper -clad steel with a nominal diameter of 5/8 inches. Ground rod sections must be a minimum of eight feet in length and manufactured for the sole purpose of providing electrical grounding.
620-2.2 Ground Rod Assembly: Provide a ground rod assembly consisting of on e or
more ground rods coupled together, such that the total length of the assembly is a minimum of 20 feet, driven into the earth at a single point, without disrupting the electrical continuity of the assembly.
620-2.3 Ground Rod Array: Provide ground rod arrays, as required, consisting of two
or more ground rod assemblies, bonded together and spaced a minimum of 40 feet apart.
620-2.4 Grounding Conductors: For installing grounding conductor in conduit, provide
an insulated conductor that is stranded in a ccordance with ASTM B8 and color code the grounding conductor green. For installing grounding conductor without conduit, provide bare solid copper wire meeting the requirements of ASTM B3 for grounding conductors. Connect the grounding conductor from the s ystem ground bus or barrier plates to the ground rod assembly. Size equipment grounding conductors according to NEC Section 250.122. Size grounding electrode conductors according to NEC Section 250.66.
620-2.5 Exothermic Grounding Bond: Make all connections to the ground rod
assemblies using exothermic welds.
620-2.6 Air Terminals: Use air terminals that comply with UL 96A and NFPA 780
standards and are listed by a NRTL .
620-2.7 Surge Protective Devices (SPDs):
Install SPDs on all p ower, data, video and any other conductive circuit. SPD requirements for lighting must meet the minimum requirements of Section 992 and the Standard Plans. Use SPDs that meet the requirements of Section 996 and are listed on the Department’s Approved Produ ct List (APL). Provide primary and secondary surge protection on AC power at traffic control device field sites.
620-2.7 1 SPD for 120 Volt or 120/240 Volt Power: Install a SPD at the utility
disconnect to the cabinet. Ensure an SPD is provided whe re the supply circuit enters the cabinet. Locate the SPD on the load side of the main disconnect and ahead of any and all electronic devices and connected in parallel with the AC supply.
620-2.7 2 SPD at Point of Use: Install a SPD at the point the ITS devices receive
120 volt power and connected in series with the circuits. FY 2023-24 Return to Table of Contents
620-2.7 3 SPD s for Low-Voltage Power, Control, Data and Signal Systems:
Install a specialized SPD on all conductive circuits including, but not limited to, data communication cables, coaxial video cables, and low -voltage power cables.
620-2.7 4 Manufacturer’s Warranty: Ensure that the SPD has a manufacturer’s
warranty cov ering failures for a minimum of 10 years from the date of final acceptance by the Engineer in accordance with 5 -11 and Section 608. The term “failure” for warranty replacement is defined as follows: Parallel-connected, power -rated SPD units are cons idered in failure mode when any of the visual indicators shows failure mode when power is applied to the terminals at the unit’s rated voltage, or the properly functioning over -current protective device will not reset after tripping. Series-connected, low-voltage power, data, or signal units are considered in the failure mode when an open circuit condition is created and no data/signal will pass through the SPD device or a signal lead is permanently connected to ground. In the event that the SPD, in cluding any component of the unit, should fail during the warranty period, the entire SPD shall be replaced by the manufacturer at no cost to the Department or maintaining agency.
620-3 Installation .
620-3.1 General: Construct a single -point grounding sys tem. Install the primary ground
rod assembly in an electrical pull box so that the top four inches are accessible for inspection, resistance testing, and maintenance. The primary ground rod assembly and electrical pull box shall be installed between 12 inches to 36 inches from the element being ground ed. The top of all other ground rod assemblies connected to the primary ground rod assembly in an array must be buried a minimum of 18 inches below grade. Direct bury grounding conductors used to connect ground rod assemblies a minimum of 18 inches below finished grade. Bond all ground rod assemblies and ground rod arrays together with solid bare tinned copper wire unless otherwise shown in the Plans. Install grounding conductors in a straight path. Make all bonds between ground wires and ground rod assemblies and ground rod arrays with an exothermic bond with the following exception: do not exothermically bond sections of ground rods to create the ground rod assembly and do not exothermic ally bond connections within a cabinet. Apply an anti -oxidant compound to all mechanical connections. Connect primary surge pro tection for power at the service entrance or main disconnect. Connect secondary surge protection at point of use, unless otherwise shown in the Plans. Ensure that lightning protection systems conform to the requirements of the National Fire Protection As sociation (NFPA) Code NFPA 780, Standard for the Installation of Lightning Protection Systems. Install SPDs that have an operating voltage appropriate for the characteristics of the circuits they protect. The NFPA requirements do not apply to lighting systems.
620-3.2 Grounding Resistance:
620-3.2 1 Minimum Resistance Required: Obtain a resistance to ground of not
more than 5 ohms for the following grounding applications. Install multiple ground rod assemblies totaling a maximum length of up to 80 feet, as required to achieve minimum grounding resistance. FY 2023-24 Return to Table of Contents
1.Power service for traffic control devices
2.Signal and ITS cabinets
3.ITS Poles/Structures with electronic equipment
4.DMS and DMS structures Install a minimum of one primary ground rod assembly. If a grounding and lightning protection system using a single g round rod assembly does not achieve the required resistance to ground, extend the length of the ground rod assembly an additional 20 feet or install an additional ground rod assembly 40 feet away and connect it to the main ground rod assembly to create a g round rod array. Continue installing ground rod assemblies connected in an array until the required resistance is obtained or until the maximum required total length of ground rod is installed. Grounding systems formed from horizontally constructed condu ctive radials are permitted if site conditions prohibit the use of vertically driven rods as permitted by the NEC
Article 250 — 53(G). A grounding system consisting of the maximum total length of ground rod
required is acceptable in cases where soil conditio ns prevent the grounding system from achieving the required resistance to ground. Submit the site resistance measurement to the Engineer.
620-3.2 2 Minimum Resistance Not Required : Install a single ground rod
assembly for the following applications . No resistance to ground measurements are required .
1.Conventional lighting
2.External lighting for signs
3.Signal cable & span wire
4.Aerial interconnect messenger wire
5.Pedestals for pedestrian signals
6.Pull boxes with metal covers w hen 120 volts (or greater) AC power is present
7.Splice boxes with wire grounding units .
620-3.3 Grounding Traffic Control Systems at Signalized Intersections: Ensure that
all separately grounded elements at an intersection (signal cabinet, power service, mast arms or strain poles, etc.) are bonded together to form an intersection grounding network array. For traffic signal poles, including pedestals for pedes trian signals, accommodate the ground connection from signal heads and electrically powered signs through span wires to the ground rod assembly or array located at the pole base in accordance with the details in the Standard Plans . For span wire assembli es, use the span wire to connect the ground rod assemblies or arrays of the poles. Do not use guy wires for grounding purposes, however bond any guy wire to the span wire as part of the intersection grounding network.
620-3.4 Grounding Traffic Control Sys tems on Highways: Install the primary ground
rod assembly at the base of the traffic control device supporting structure. Bond all metal components of the system (such as cabinets, steel poles, and concrete pole grounding wire) to the grounding system usin g a mechanical connection on the equipment side and an exothermically welded connection at the down cable. Do not use split bolts for grounding system connections. Connect all ground rod assemblies and any associated grounded electrical system within a 1 00 foot radius (but not beyond the edge of the roadway) of the primary ground rod assembly. Connect the primary ground rod assembly to a single point main grounding bar inside FY 2023-24 Return to Table of Contents the equipment cabinet or mount it to the base of the traffic control device supp orting structure unless otherwise shown in the Plans. Place multiple ground rod assemblies , as required, in a ground rod array as depicted in the Standard Plans unless otherwise shown in the Plans. If a required array cannot be placed in the right of way, submit an alternate placement detail for approval.
620-3.5 Grounding Highway Lighting Systems: Ground each metal light pole.
For poles on bridge structures, bring the grounding conductors out to a pull box at each end of the structure and connect them to driven ground rods 20 feet in length. Ground all high mast poles in accordance with the details for grounding in Standard Plans, Index 715-010.
620-3.6 Grounding Equipment Shelters: Install all grounds for the equipment shelter
on the side of the building that utilities, communication cables, and fiber enter. Connect all earth grounds to this point, including the grounding system for SPDs. Make all connections to SPDs according to th e manufacturer’s recommendations. Ensure that communication cables, AC power, emergency generator, and equipment frames are connected by the shortest practical route to the grounding system. Protect the lead lengths from each device to the SPD. Use compression type connection for all interior connections to bond ground ing conductors to equipment in the shelter. For connections to bus bars, use mechanical connections having two bolts on a double -lug connector. Install star washers, or another means that accommodates the fasteners used and achieves reliable electrical connections that will not deteriorate. Crimp and solder all wires connected to lugs or clamps. Verify electrical continuity of all connections. Remove all non -conducting surface coatings befo re each connection is made. Ensure that ground conductors are downward coursing, vertical, and as short and straight as possible. Ensure that the minimum bending radius for interior equipment shelter grounds is eight inches. Avoid sharp bends and multipl e bends in grounding conductors.
620-3.6 1 Interior Grounding: Install a No. 2 AWG solid bare copper wire
approximately one foot below the ceiling on each wall and mount it using insulated standoffs. Ensure that the wire encircles the equipment room, for ming a ring or continuous loop. Mechanically connect the cable trays to the interior perimeter ground using stranded copper wires with green insulation and bolted terminal connectors at the cable tray ends. Make all points where cable tray sections meet el ectrically continuous by use of a short jumper wire with terminals attached at each end. Directly bond all other metallic objects, such as door frames and doors, air conditioners, alarm systems, wall -mounted communication equipment, etc., to the closest interior perimeter ground with the shortest possible stranded copper wire with green insulation. Bond the door to the doorframe using flexible welding cable.
620-3.6 2 Exterior Grounding: Install an exterior grounding system consisting
of multiple groun d rod assemblies around the exterior perimeter of the equipment shelter . Place the ground rod assemblies a minimum of two feet from the building foundation in a suitable access point. Bond the following items to the shelter’s grounding system:
1.Metal building parts such as downspouts and siding.
2.Ground rods provided by power or telephone utilities for grounding of AC power or surge protection devices, as permitted by local codes.
3.Shelter support skids, bases, or foundations, if applicable.
4.Any metal object larger than four square feet. FY 2023-24 Return to Table of Contents
5.External metal fencing.
620-3.6 3 Punch Block SPD Grounding: Ground Type 66 punchdown blocks in
accordance with the manufacturer’s recommendations and mechanically connect them to the shelter’s i nterior perimeter ground.
620-3.6 4. Equipment Shelter Fence Grounding : Ensure that the metal Type B
fence is grounded to fence perimeter ground ing conductors consisting of No. 2 AWG solid bare tinned copper wires that encircle the entire compound to achieve required resistance to ground required in 620 -3.2. Exothermically bond any splices in the ground ing conductors . Bury the fence perimeter ground ing condu ctor a minimum of 2.5 feet below finished grade. Bond all fence posts to the fence perimeter ground wire using No. 2 AWG solid bare tinned copper wire. Bond the gate and gatepost together with a flexible ground, such as welding cable wires. Ground the gatepost to the fence perimeter ground wire using No. 2 AWG solid bare tinned copper wire. Exothermically bond all connections to the fence perimeter ground wire. Connect the fence’s top rail to each corner post and in the middle of each side. Ground the fe nce fabric with No. 2 AWG solid bare tinned copper wire connected to the fence posts. Connect the fence perimeter wires to the ground rod assemblie s of the equipment shelter’s ground system with No. 2 AWG solid bare tinned copper wire, as shown in the Plans. Ensure that all ground leads are No. 2 AWG solid bare tinned copper wires for all above - and underground grounding wire installations. Ensure that all exothermic bonds are appropriate for the application. Do not use welding or other forms of bonding without prior written approval.
620-4 Ground Resistance Testing and Inspection.
620-4.1 Testing: Measure the ground resistance with an instrument designed specifically
to measure and document earth/ground resistance, soil resistivity, and current flow. Co nduct the test by using the fall -of-potential method as described in the Institute of Electronic and Electrical Engineers (IEEE) Standard 81. The fall-of-potential test is used to verify the minimum resistance required in 620 -3.2.1. If fall-of-potential te sts cannot be performed, it is acceptable to measure resistance at each accessible ground rod using a clamp -on ground resistance tester. Submit to the Engineer certified test results for each testing location. Submit the following information on the test results:
1.The formal name or ID for the location where the test was performed
2.The GPS latitude and longitude for the location where the test was performed
3.The date on which the test was performed
4.The make and model number, serial number, and last date of calibration (by an independent testing facility within the previous 12 months) for the grounding resistance testing device used
5.Contact information (including name, signature, and employer name) for each person conducting, wit nessing, or certifying the test
6.Description of the local environmental and soil conditions at the time of testing
7.A rough sketch of the site grounding system; along with the corresponding measured data points
8.Page numbering showing the current page number and total page count (e.g., Page 1 of 3) Only clamp -on ground resistance testing is required for roadway lighting installations. FY 2023-24 Return to Table of Contents
620-4.2 Inspection: Do not backfill below -grade grounding installations and grounding
connections until inspected and approved. The Engineer will inspect the installation for proper connection types, tightness, workmanship, and conformance to the Plans. Replace any exothermic bonds that are deemed unsatisfactory with new exothermic bonds. Repair or replace any mechanical connections that are deemed unsatisfactory. Measure the resistance at each accessible ground rod using a clamp -on earth tester. The measurement at any individual rod is the cumulative resistance of all rods in a parallel circuit. For ground ing system inspections, notify the Engineer at least five days prior to completion of the installation. Record all test results in a standardized format approved by the Engineer prior to testing. All recorded test report data shall be dated, witnessed, and signed by at least one representative of the Department and the Contractor. Remedy all deficiencies at no cost to the Department.
620-5 Basis of Payment.
The work specified in this Section will not be paid for directly, but will be considered as incidental work. FY 2023-24 Return to Table of Contents SECTION 630 CONDUIT
630-1 Description.
Furnish and install conduit for traffic control signals and devices, highway lighting, and other electrically powered or operated devices as shown in the Contract Documents .
630-2 Materials.
630-2.1 Conduit: Use materials that have been tested and listed by a Nationally
Recognized Testing Laboratory to the following industry standards: Schedule 40 and 80 Polyvinyl Chloride (PVC)1 ................... UL 651 Fiberglass Reinforced Epoxy2 ................................ ............. UL 2420 Intermediate Metal3 ................................ ............................. UL 1242 Rigid Galvanized Metal3,4 ................................ ......................... UL 6 Rigid Aluminum4 ................................ ................................ ... UL 6A PVC Coated Intermediate Metal4................... ASTM A135/A135M, .................. ASTM A513, ASTM A568/A568M, NEMA RN1-2005 Liquid Tight Flexible Metal ................................ .................. UL 360 High Density Polyethylene (HDPE) Standard Dimension Ratio (SDR) 9 -115 ................................ ....................... ASTM F2160 HDPE SDR 13.55 ................................ . ASTM F2160, NEMA TC-7 Schedule 40 and 80 HDPE ................................ ................. UL 651A
1.Use conduit with solvent weld slip-fit plastic couplings unless approved by the Engineer.
2.Use conduit having a minimum stiffness value of 250. Ensure that each section has a duct bell with an integral gasket on one end and a duct spigot on the other end.
3.Use conduit that is hot -dipped galvani zed with a minimum coating of 1.24 ounces per square foot on both the inside and outside of the conduit . The weight of the zinc coating shall be determined using ASTM A90.
4.Use conduit with both ends reamed and threaded.
5.Can be used with preassemb led cable and rope -in-conduit.
630-2.2 Locate Wire: Ensure that locate wire is a single copper conductor with a
minimum gauge of No. 12 AWG. Ensure locate wire is insulated using a 45 mil minimum thickness polyethylene sheath that is orange in color and m arked to identify the manufacturer and the conductor size.
630-2.3 Locate Wire Grounding Unit : Ensure that locate wires are attached to a wire
grounding unit ( WGU) dedicated to safely dissipat e high transient voltages or other foreign electrical surges induced into the designat ed system. Ensure the WGU conforms to the following:
1.Allows signals generated by locate system transmitters to pass through the protection system without going to ground .
2.The protection system automatic ally resets and passes locate system transmitter signals after the unit has been grounded to dissipate over -voltages.
3.Is intended for below or above grade applications. Ground the WGU to a driven rod within 10 feet of the system using a No. 6 AWG single conductor wire with green insulation. FY 2023-24 Return to Table of Contents
Source: Florida Standard Specifications for Road and Bridge Construction, 2024 Edition. Pages 837–842 of 1,299.