Exhibit_H_-_Grounding_and_Bonding_and_Surge_Protection_Requirements.pdf
PDF 120 KB Posted
- Solicitation number
- RFP 126FO005
- Issued by
- Denver County, Denver City, Colorado
About this file
This is a technical specification document outlining grounding and bonding requirements for equipment installations by the Regional Transportation District (RTD) in Denver, Colorado, in connection with the Ticket Vending Machine (TVM) Replacements project. The specification establishes minimum National Electrical Code-compliant standards for outdoor equipment cabinets, including new Ticket Vending Machines and Communications Cabinets. Key requirements include installation of a Grounding Electrode System (GES) at each cabinet location with a minimum single ground rod (or supplemental rods spaced at least 6 feet apart to achieve less than 5 Ohms resistance), bonding of all metal enclosures and interior components to grounding and equipment grounding conductors, isolation of neutral conductors at subpanels, and bonding of internal equipment such as UPS systems, network switches, metallic racks, and conduits. Communications systems must be bonded to the same cabinet GES, including metallic conduits, telecom ground bars, and cable entrance protection devices.
The specification further requires surge protection through Protection Equipment Terminal (PET) devices installed within each equipment case, with the contractor responsible for furnishing and installing all PET devices. Additional integration considerations address the rail platform grounding grid to ensure comprehensive electrical safety across the RTD service area. These grounding and bonding requirements apply to the overall TVM replacement project, which involves removal of 185 existing machines and installation of 173 new TVMs at various RTD locations including existing TVM sites, the East Colfax Bus Rapid Transit corridor, Civic Center Station, and designated spare units, with an optional purchase of 6 additional TVMs for Denver Union Station Bus Concourse.
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Text version
Grounding and Bonding Requirements
All Grounding and Bonding installation requirements shall meet National Electrical Code.
Below is the list of minimum requirements that shall be considered for the intended installations. Equipment Cabinets listed below shall apply to either new Ticket Vending Machines OR new Communications Cabinets.
A) Cabinets:
The cabinet is outdoors and remote from a building, it is treated as a separate structure.
Minimum requirements shall be:
(a) A Grounding Electrode System (GES) at the cabinet location
Install a grounding electrode system.
Typical GES for outdoor cabinets:
Minimum single ground rod. If supplemental ground rod is required it shall be min ≥6 ft apart to achieve less than 5 Ohms resistance.
#6 Cu minimum grounding electrode conductor
(b) An equipment grounding conductor (EGC) must be run with the feeder
(c) Neutral must be isolated
No neutral-to-ground bond in the cabinet (only at the service disconnect).
B) The Cabinet’s Metal Enclosure shall Be Bonded:
The cabinet (metal enclosure, doors, frames, interior panels) shall be bonded to:
The grounding electrode conductor (GEC)
The equipment grounding conductor (EGC)
A grounding/bonding bar installed inside the cabinet
Bonding must ensure a low-impedance fault-current path.
C) If a Panelboard is installed inside the cabinet:
If the cabinet contains a panelboard:
Minimum requirements shall be:
It is a subpanel → neutral isolated, ground and neutral separate.
Feeder must bring ungrounded conductors + neutral (if needed) + EGC
Bond panelboard enclosure to the cabinet ground bar
No bonding screw in the neutral bar
Where utility power drops directly to the cabinet, a disconnecting means may apply.
D) Bonding Internal Equipment (UPS, Switches, Racks, Conduits) inside the Cabinets.
Bond:
UPS chassis (hardwired UPS must have EGC terminal)
Network switches and chassis equipment (via rack bonding)
All metallic rack rails
Any metallic wireways
All metallic conduits entering/leaving the cabinet
Surge protection devices
E) Communications Grounding & Bonding
Communications systems must be bonded to the same cabinet GES.
This includes:
Minimum requirements:
Metallic conduit containing comms cables
Any telecom ground bar (TGB or TBB) inside cabinet
Cable entrance protection (protectors/SPDs)
F) Additional Rail-Platform Considerations
• Integration with the rail platform grounding grid.
Surge Protection Functional Requirements:
New RTD Equipment Case:
All existing equipment that will connect to the Ethernet ports of the IT switch must be routed through a Protection Equipment Terminal (PET) device. The PET devices shall be installed within the Equipment Case. The Contractor shall furnish and install all PET devices.
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