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This chapter describes the steps to take and the considerations you should keep in mind prior to installing the modules in an open rack. It also contains information that applies to an MGX 8850 installation in a Cisco closed rack. If the switch arrives in a Cisco closed rack, your initial concerns would be the cabinet grounding, power connections, and optional seismic stability plate. For specifications on the enclosure and power system, see "System Specifications."
Before proceeding with the installation, verify that all the ordered parts are present and in good condition. Store a record of the parts and serial numbers. If any parts are missing or damaged, contact your sales representative.
Slots 7 and 8 are reserved for the primary and redundant Processor Switching Modules (PXM45s). These slot reservations reflect a redundant configuration for these cards. The maximum number of slots remaining for service modules is 12.
In addition to the power and grounding requirements detailed in subsequent sections, the site must satisfy requirements in the following categories:
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Caution If you move a Cisco-supplied cabinet, do not push it at its sides. Push at the front or back. |
An optional stability plate can be purchased with the Cisco cabinet to bolt the cabinet to the floor. Instructions for installing the stability plate appear in "Seismic Anchoring for a Cisco Rack" later in this chapter.
This section describes the requirements for electrical power and grounding at the switch and the site. These requirements apply to Central Office (CO) and Private Enterprise (PE) sites.
The MGX 8850 AC power requirement is 220 VAC (180-264 VAC). See also "System Specifications." The AC power source must be within 6 feet (1.8 m) of the system and easily accessible. Before turning on the power, verify that the power supplied to the node comes from a dedicated branch circuit.
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Caution Consult Customer Service if the plans for MGX 8850 AC power include an uninterruptible power source (UPS). Cisco recommends a UPS with a low output impedance and the capacity to provide the necessary fault current to trip the protection devices. Do not use a UPS or any power source with a Ferro-Resonant transformer. |
The power receptacles to which the node connects must be of the grounding type. The grounding conductors that connect to the receptacles should connect to protective earth at the service equipment. For reference, Figure 3-1 shows the hookup schematic in the three-wire wall plug.
Cisco can provide AC power cords with the following plugs:
AC power sources must be a dedicated AC branch circuit. Each branch circuit must be protected by a dedicated two-pole circuit breaker. The circuit breakers at the source must have a rated trip delay time greater than those of the MGX 8850 circuit breaker with a medium trip delay. The MGX 8850 switch uses a 20-Amp, 2-pole circuit breaker for each AC input. Cisco recommends that the site have a 20-Amp, 2-pole AC circuit breaker with a long trip-delay at each branch circuit.
The DC-powered model of the MGX 8850 uses one or two Power Entry Modules (PEMs) for connection to DC power source. The DC PEMs should each be connected to a dedicated source capable of supplying 60 amps of current. Each branch circuit should have a 60-amp circuit breaker at the source. Wires connecting the PEMs to the sources should be capable of carrying 60 amps. A 6 AWG (10 square millimeters) copper wire is recommended. Consult the local or national codes for conductor sizing for DC supply connections if necessary.
Be sure to connect the grounding wire conduit to a solid earth ground. Cisco recommends a ring terminal lug to terminate the ground conductor at the ground stud. For details, see "Bonding and Grounding the MGX 8850" in Appendix D.
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Caution The -48 VDC return is connected to the equipment chassis along with logic and safety grounds; therefore, the chassis ground must be solidly connected through a low impedance connection to the earthing ground. |
Additional requirements are as follows:
DC-power sources must be a dedicated DC branch circuit. Each branch circuit must be protected by a dedicated circuit breaker. The circuit breaker must have a rated trip delay time greater than those of the MGX 8850 circuit breaker. DC-powered nodes use a 60-Amp, 1-pole circuit breaker with a short trip delay on each -48-V input. Cisco Systems recommends the site have a dedicated 60-Amp, 1-pole circuit breaker with a medium trip delay at each branch circuit.
This section describes how to install the Cisco cabinet with the optional stability plate for seismic anchoring. If you have no stability plate, go to "Enclosure and Card Installation."
Perform the following steps to set up the Cisco cabinet with the stability plate:
Step 2 Remove the stability plate from the base of the Cisco cabinet. Save these nuts and bolts.
Step 3 With the user-provided anchoring bolts, attach the stability plate to the floor.
Step 4 Roll the Cisco cabinet over the stability plate illustrated in Figure 3-3.
Step 5 Use the nuts and bolts removed in Step 2 to secure the cabinet to the stability plate.
This section describes the steps for making ground connections that comply with Cisco grounding policies. The descriptions cover optional ground connections from each node to the ground connector of the rack as well as the equalization connections between racks that are part of the earth grounding network.
The Cisco-supplied cabinet has two pairs of grounding studs and the hardware for securing a ground conductor to the studs at the top and bottom of the cabinet. The studs measure 1/4" by 20 threads per inch. The studs can accept a two-holed grounding connector designed to prevent rotation and possible loosening of the connector. Figure 3-4 shows the Cisco cabinet with the ground attachment studs in the upper and lower parts of the cabinet. A ground symbol on the Cisco rack indicates the points of attachment.
Perform the following steps to attach a ground conductor to the frame of a Cisco rack:
Step 2 Place the connector terminating the grounding conductor closed-loop ring or two-hole compression fitting onto the stud.
Step 3 Place another external, toothed star washer or lock washer onto the stud.
Step 4 Screw a nut onto the threaded stud.
The MGX 8850 switch ships with a wrist strap for grounding the user and protecting the electronic components from electrostatic shock. The wrist strap kit consists of a strap, a coiled cord, and a clip for holding the strap.
Cisco recommends you install the base of the wrist strap cable on the left front flange of one of the units at a convenient height:
Step 2 Peel the back off the clip to expose the adhesive surface and attach to the front of the unit above the ring lug.
Step 3 Mount the clip sideways to allow the strap to be held in a position that will not interfere with the removal of cards. Use the clip to store the strap.
Different Cisco products can reside in the same rack. If a multi-system rack configuration includes an MGX 8600-series switch, it should be located as the bottom unit.
Posted: Mon Jul 31 09:56:43 PDT 2000
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