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Grounding the chassis

Before connecting cables or powering the Flex System Carrier-Grade chassis, you must connect the chassis to earth ground.

Statement 29

Graphic illustrating Safety Statement 29
This equipment is designed to permit the connection of the earthed conductor of the dc supply circuit to the earthing conductor at the equipment. If this connection is made, all of the following conditions must be met:
  • This equipment shall be connected directly to the dc supply system earthing electrode conductor or to a bonding jumper from an earthing terminal bar or bus to which the dc supply system earthing electrode conductor is connected.
  • This equipment shall be located in the same immediate area (such as, adjacent cabinets) as any other equipment that has a connection between the earthed conductor of the same dc supply circuit and the earthing conductor, and also the point of earthing of the dc system. The dc system shall not be earthed elsewhere.
  • The dc supply source shall be located within the same premises as this equipment.
  • Switching or disconnecting devices shall not be in the earthed circuit conductor between the dc source and the point of connection of the earthing electrode conductor.

Statement 34

To reduce the risk of electric shock or energy hazards:
  • This equipment must be installed by trained service personnel in a restricted-access location, as defined by the NEC and IEC 60950-1, First Edition, The Standard for Safety of Information Technology Equipment.
  • Connect the equipment to a properly grounded safety extra low voltage (SELV) source. A SELV source is a secondary circuit that is designed so that normal and single fault conditions do not cause the voltages to exceed a safe level (60 V direct current).
  • Incorporate a readily available approved and rated disconnect device in the field wiring.
  • See the specifications in the product documentation for the required circuit-breaker rating for branch circuit overcurrent protection.
  • Use copper wire conductors only. See the specifications in the product documentation for the required wire size.
  • See the specifications in the product documentation for the required torque values for the wiring-terminal screws.
The following circuit breaker and ground cable ratings apply to chassis equipped with -48 V dc power supplies:
BreakerListed 70 ASee Note 1
Ground cable4 AWG with Listed lug which can accept M6 ground screwsSee Note 2
Torque rating for ground screws4.0 - 4.8 Newton-meters (35.4 - 42.5 inch-pounds)-
  1. The maximum steady state current of the -48 V dc power supply is less then 70 A. However during specific events, such as over subscription, it is possible for the power supply to briefly draw a current greater than 70 A. Therefore it is recommended that the power supply be protected by a Listed circuit breaker that will support up to 90 A for a minimum of 20 ms. The suggested Telect High Current Panel Dual 350A Power Distribution Panel (part number 350CB06) using the Telect 70 A circuit breakers (Part number 090-0052-0070) conforms to this specification.
  2. If not connecting to a SELV source which provides Reinforced insulation you must use a Ground Cable.
To connect the chassis to earth ground, complete the following steps:
  1. Connect an earth ground cable to the ground studs on the rear of the chassis:
    Illustration showing how to attach the ground cable
    1. Use a 10 mm nut driver to remove the hex nuts from the ground studs.
    2. Remove the lock washer and one of the flat washers from each ground stud.
    3. Push the ground lug onto the ground studs; then, place the flat washer, the lock washer, and the hex nut back on each ground stud.
    4. Use a 10 mm nut driver to tighten the hex nuts to 4.0 - 4.8 Newton-meters (35.4 - 42.5 inch-pounds).

See Cabling the chassis and Connecting the chassis to power for more information.