Part 2: Connect Power to the Switch
Depending on the model, you can use either AC or DC power supplies. The power supplies are hot-removable and hot-insertable field-replaceable units installed in the rear panel of the switch. You can replace them without powering off the switch or disrupting switch functions.
Do not mix AC and DC power supplies in the same switch.
Grounding is required for models that use DC power supplies and recommended for models that use AC power supplies. An AC-powered switch gets additional grounding when you connect the power supply in the switch to a grounded AC power source outlet by using the power cord.
Ensure that you understand how to prevent ESD damage (see Prevention of Electrostatic Discharge Damage).
To connect power to an AC-powered switch (for each power supply):
- Locate the power cord that has a plug appropriate for your geographic location.
- wrap and fasten one end of an ESD wrist strap around your bare wrist, and connect the other end of the strap to the ESD point on the switch.
- Insert the coupler end of the power cord into the AC power cord inlet on the power supply.
- Push the power cord into the slot in the adjustment nut
of the power cord retainer clip. Turn the nut until it is tight against
the base of the coupler (see Figure 8).
Figure 8: Connecting Power to an AC-Powered Switch 
- If the AC power source outlet has a power switch, set
it to the off position.
Note Each power supply must be connected to a dedicated AC power feed with a dedicated customer-site circuit breaker. We recommend that you use a dedicated customer-site circuit breaker rated for either 15 A (110 VAC) minimum or 10 A (220 VAC) minimum, or as required by local code.
- Insert the power cord plug into the power source outlet.
- Dress the power cord appropriately. Ensure that it does not touch the switch components, block the air exhaust and access to switch components, or drape where people could trip on it.
- Switch on the dedicated customer-site circuit breaker.
- If the AC power source outlet has a power switch, set it to the on position.
- Verify that the status LED on the power supply faceplate is on and steadily lit green.
You connect DC power to the switch by attaching power cables from the DC power source to the terminals on the power supply faceplate.
A licensed electrician must attach the ring lugs to the DC power cables.
Before connecting the switch to a DC power source, ensure that the cable leads will not become active while you are connecting DC power and that the voltage across the DC power source cable leads is 0 V. Locate the input circuit breaker on the panel board that provides DC power, set the circuit breaker to the off position, and tape the switch handle of the circuit breaker in the off position. We recommend that you use a dedicated customer-site circuit breaker rated for 40 A (–48 VDC) minimum, or as required by local code.
Before you connect power to the switch, wrap and fasten one end of an ESD wrist strap around your bare wrist, and connect the other end of the strap to the ESD point on the switch.
To connect power to a DC-powered switch (for each power supply):
- Switch off the dedicated customer-site circuit breakers. Ensure that the voltage across the DC power source cable leads is 0 V and that the cable leads do not become active during installation.
- Verify that the DC power cables are correctly labeled
before making connections to the power supply. In a typical power
distribution scheme where the return is connected to chassis ground
at the battery plant, you can use a multimeter to verify the resistance
of the
–48VandRTNDC cables to chassis ground:The cable with very large resistance (indicating an open circuit) to chassis ground is –48V.
The cable with very low resistance (indicating a closed circuit) to chassis ground is RTN.
Caution You must ensure that power connections maintain proper polarity. The power source cables might be labeled
(+)and(–)to indicate their polarity. There is no standard color coding for DC power cables. The color coding used by the external DC power source at your site determines the color coding for the leads on the power cables that attach to the terminal studs on each power supply. - Remove the nuts from the terminals. Save the nuts.
Caution Ensure that each power cable lug seats flush against the surface of the terminal block as you are tightening the nuts. Ensure that each nut is properly threaded into the terminal. Applying installation torque to the nuts when improperly threaded can result in damage to the terminal.
Caution The maximum torque rating of the terminal screws on the DC power supply is 6 lb-in. (0.68 Nm). The terminal screws might be damaged if excessive torque is applied. Use only a torque-controlled driver to tighten screws on the DC power supply terminals. Use an appropriately sized driver, with a maximum torque capacity of 6 lb-in. (0.68 Nm) or less. Ensure that the driver is undamaged and properly calibrated and that you have been trained in its use. You may want to use a driver that is designed to prevent overtorque when the preset torque level is achieved.
- Secure each power cable lug to the terminal with the nuts
by using a socket nut driver (see Figure 9). Do not overtighten the
nuts. Apply between 5 lb-in. (0.6 Nm) and 6 lb-in.
(0.68 Nm) of torque to the nuts.
Secure the positive (+) DC source power cable lug to the return terminal (labeled
RTN).Secure the negative (–) DC source power cable lug to the –48V terminal (labeled
–48V).
Figure 9: Connecting Power to a DC-Powered Switch 
- Verify that the power cabling is correct. Ensure that cables do not touch the switch components, block the air exhaust and access to switch components, or drape where people could trip on them.
- Connect each DC power cable to the appropriate external DC power source.
- Switch on the dedicated customer-site circuit breakers.
- Verify that the status LED on the power supply faceplate is on and steadily lit green.