Grounding Considerations
Prior to starting the installation of the Tellabs 1100 Series OLT Shelves, Tellabs 1150 (MDS5) or Tellabs 1150E (MDS7), and related equipment, ensure that the facility grounding system is installed in accordance with:
- EIA-310-D Cabinets, Racks, Panels, and Associated Equipment
- CEA-310-E Design Requirements for Cabinets, Panels, Racks and Subracks
- IEC 60297 Mechanical Structures for Electronic Equipment
- EIA/TIA-607 Grounding and Bonding Requirements for Telecommunications in Commercial Buildings
- United States Department of Agriculture Rural Utilities Service (RUS) Bulletin 1751F-810
- Electromangetic Compatibility (EMS) and Electrical Safety, GR-1089-CORE, Bonding and Grounding
- and/or local practices.
Enterprise Deployment
Typical Enterprise deployments are Gigabit Passive Optical Network (GPON) based installations consisting of Quad-port Optical Interface Units (QOIU7s).
Typically, the equipment rack is powered by a local AC powered +48VDC Rectifier shelf, (e.g., the Valere DC Rectifier shelf.).
Telecommunication Company Deployment
Typical Telecommunication Company (Telco) deployments may contain GPON and DS1, as well as outside plant support (OSP) capabilities. OSP support consists of Digital Subscriber Line (DSL) and/or Plain Old Telephone Service (POTS). In Tellabs® MSAP shelves, these are supported by the installation of a Node Data Controller (NDC), Node Voice Controller (NVC), and/or Node Multiservice Controller (NMC).
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Note: 1100 Series Optical LAN installations do not support DS1 or OSP services. |
Typically, the equipment rack is powered by a -48VDC Battery system located in the facility.
Refer to the following procedures and illustration to determine the grounding scheme appropriate for the applications being supported.
- Typical deployment is with a local AC powered DC Rectifier shelf, e.g., Valere DC Rectifier:
- Without OSP connections, connect Digital Grounds (DGND) to Telecom rack.
- Typical deployment is with a local Breaker/Fuse Panel and +48VDC Battery:
- Without OSP connections, connect Digital Grounds (DGND) to Telecom rack.
In all cases:
- Equipment chassis (safety) grounds shall be connected to the Telecom rack;
- All grounds shall be continuous and routed in the shortest possible straight-line path.
- Telecom rack shall be connected to the Telecom Ground Bar (TGB) or Ground Window Bar (GWB), with a minimum #6AWG ground cable, which shall be connected to the Telecom Master Ground Bar (TMGB) or Master Ground Bar (MGB), in accordance to the applicable specification;
Originally, rack mounting holes were tapped to receive a particular type of threaded bolt. This is still frequently used in some government and military applications, often in conjunction with slide rails for ease of maintenance. However, it is no longer typical for frequently changed server racks, due to the possibility for the threads to become damaged or for a bolt to bind and break off, rendering the mounting hole unusable. Tapped-hole racks are still used for hardware that rarely changes, such as phone, network cabling panels, TV broadcasting facilities, studios and relay racks.
The tapped-hole rack was first replaced by clearance-hole (Round Hole, Round Unthreaded Holes, Versa Rail) racks. The holes are large enough to permit a bolt to be freely inserted through without binding, and bolts are fastened in place using cage nuts. A cage nut consists of a spring steel cage, designed to clip onto the open mounting hole, within which is a captive nut. In the event of a nut being stripped out or a bolt breaking, the nut can be easily removed and replaced with a new one.
Additionally, there are square-hole racks which allow boltless mounting, such that the rack-mount equipment only needs to insert through and hook down into the lip of the square hole. Installation and removal of hardware in a square hole rack is very easy and boltless.
If any of the non-tapped options exist with the rack the equipment is being mounted in, a ground bar must be installed in the rack. This ground bar should meet the applicable specification(s) listed in Grounding Consideration.
This ground bar must first be connected to the nearest TGB/GWB, using 6AWG copper wire, for connection to the building ground plane. When installing the equipment in the rack, instead of grounding to the rack, construct a chassis ground cable, long enough to reach the ground bar installed in the rack, and attach these grounds to the ground bar.
For locally powered racks without using NVC, NDC and NMC cards, use the grounding scheme on the left (A); and for remotely powered racks without using NVC, NDC and NMC cards, use the grounding scheme on the right (B), illustrated below.
