Cisco Catalyst 9400 Series Hardware Installation Manual page 45

Preparing for Installation
• All power connection wiring should conform to the rules and regulations prescribed by the National
Electrical Code (NEC), as well as local codes, if any.
• The DC return must remain isolated from the system frame and the chassis (DC-I).
The color coding of the source DC power cable leads depends on the color coding of the site DC power
source. Typically, green or green and yellow stripes indicate that the cable is a ground cable. Since there
is no color code standard for source DC wiring, you must ensure that the power cables are connected to
the DC-input power supply terminal block in the proper + and - polarity.
In some cases, the source DC cable leads might have a positive (+) or a negative (–) label. This label is
a relatively safe indication of polarity, but you must verify the polarity by measuring the voltage between
the DC cable leads. When measuring, ensure that the positive lead and the negative lead always match
the "+" and "-" labels on the DC-input power supply terminal block, respectively.
• DC power cables must be terminated by cable lugs at the power supply end.
• The circuit must be protected by a dedicated two-pole DC-rated circuit breaker.
The circuit breaker is considered to be the disconnect device and must be easily accessible. For DC-input
power supply modules with multiple inputs, each DC input must be protected by a dedicated DC-rated
circuit breaker or a fuse.
The circuit breaker or fuse should be sized according to the power supply input rating and local or national
code requirements.
• If the DC inputs are powered from separate sources, the cables must be wired straight across to their
respective sources and terminals.
Crossed cables in a setup where the DC source has floating outputs means that no damage will occur,
but the LEDs will not light up, and the module will not operate.
Crossed cables in a setup with a positive ground or a negative ground power system constitute a severe
safety hazard that includes causing electric shock and generating excessive EMI and RFI.
The following illustrations show the correct installation with two separate sources of DC power and a
single source of DC power:
Warning This product requires short-circuit (overcurrent) protection, to be provided as
part of the building installation. Install only in accordance with national and local
wiring regulations. Statement 1045
Warning
This product relies on the building's installation for short-circuit (overcurrent)
protection. Ensure that the protective device is rated not greater than these values
for the U.S. and EU:
• 20 A circuit breaker for an AC-input power supply module.
• 50 A DC-rated circuit breaker for each input of a DC-input power supply
module, for safety purposes - irrespective of whether the inputs are power
from a single or separate DC sources.
Statement 1005
Power Connection Guidelines for DC-Powered Systems
Cisco Catalyst 9400 Series Switches Hardware Installation Guide
39