•
Full redundancy (
n
+1 and grid redundancy)
—
Add enough power supplies (reserve power supplies) to at least equal
the output of the active power supplies (number of power supplies calculated in Step 2). For power supply (
n
+1)
redundancy, ensure that . For input-source (grid) redundancy, you will probably double the number of power
supplies. You must plan for a second power source with at least the same amount of input power for the reserve
power supplies. Either one of the reserve power supplies can replace any of the active power supplies.
Step 4
Be sure that the power source circuits are dedicated to the switch and not to other electrical equipment.
For combined power mode (no power redundancy) or power supply (
n
+1) redundancy, you need only one dedicated
circuit. The requirements for each circuit are listed in the following table.
Table 1: Circuit Requirements for 3-kW Power Supplies
Requirement for Each Circuit
Number of
Circuits
Power Supply
AC Power Supplies
20 A at 110 VAC or 220 VAC
1
(N77-AC-3.0KW)
3-kW power supply
DC Power Supplies
20A
1
(N77-DC-3.0KW)
3-kW power supply
Table 2: Circuit Requirements for 3.5-kW HVAC/HVDC Power Supplies
Requirement for Each Circuit
Number of
Circuits
Power Supply
20 A at 110 VAC, 210 VAC, 220/230 VAC and
277 VAC or 20 A at 210 VDC, 220/240 VDC
and 380 VDC
1
(N77-HV-3.5KW)
3.5-kW
HVAC/HVDC power
supply
Step 5
Plan the placement of the input power receptacles within reach of the power cables used for each power supply (see the
following table for the maximum distances).
Typically, power receptacles are placed on the rack with the switch. If the DC power source is further than allowed by
the DC power cables, you can install a power interface unit (PIU) in the rack with the switch and connect that to the
power source with other cabling.
Maximum Distance Between Receptacle and Power Supply
Power Supply
12 feet (3.6 m)
All AC power supplies
14 feet (4.26 m)
HVAC/HVDC 3.5-kW power
supplies
Determined by the length of the power cord that you supply.
DC 3-kW power supplies
Cisco Nexus 7702 Hardware Installation Guide
7
Preparing the Site
Planning for Power Requirements
