Adding PSU to Running 3850 Switch

[ryders1]

I have a pair of stacked 3850s that are powered by two PSU connected to the same UPS. I need to replace that UPS and I am wondering if it is possible to add a PSU to spare slot in each switch and connect it to a different UPS. The device is critical to operations even during a maintenance window so I'm hoping to find a way to add redundant power to it without bringing it offline. I found an article that refers to PSU as hot swappable, but I'm not confident that means you can add them while the device is online. The switch stack is connected with data stacking and power stacking cables.

My current plan would be to put the switch in redundant power mode, then add the PSU one at a time. Then connect the two new PSU to a different UPS and replace the old UPS. I have a case open with cisco TAC but they have ignored this question twice in their responses so I'm hoping to get an answer here. The new power supplies are 715 watt.

Catalyst 3850 Switch Hardware Installation Guide - Power Supply Installation [Cisco Catalyst 3850 Series Switches] - Cisco

Switch-Stack#sho stack-power detail
Power Stack Stack Stack Total Rsvd Alloc Sw_Avail Num Num
Name Mode Topolgy Pwr(W) Pwr(W) Pwr(W) Pwr(W) SW PS
-------------------- ------ ------- ------ ------ ------ ------ ----- ----
Powerstack-1 SP-PS Ring 700 30 460 210 2 2

Power stack name: Powerstack-1
Stack mode: Power sharing
Stack topology: Ring
Switch 2:
Power budget: 230
Power allocated: 230
Low port priority value: 22
High port priority value: 13
Switch priority value: 4
Port 1 status: Connected
Port 2 status: Not connected
Neighbor on port 1: Switch 1 - ccd8.c131.f980
Neighbor on port 2: 0000.0000.0000

Switch 1:
Power budget: 230
Power allocated: 230
Low port priority value: 21
High port priority value: 12
Switch priority value: 3
Port 1 status: Connected
Port 2 status: Not connected
Neighbor on port 1: Switch 2 - ccd8.c172.5f80
Neighbor on port 2: 0000.0000.0000

Switch-Stack#

[marce1000]

            >...but I'm not confident that means you can add them while the device is online.
   - You can , check the logs when changing adding , removing , ...PSU's  on the 3850 too , to confirm correct result according to intended operation(s)

                      >...TAC but they have ignored this question ..
   - Now if you say that the device is critical , then TAC can be a 'point of responsibility and can be held responsible for correct  procedures ' w.r.t business availability  ; if you rely on answers here ; then anyone can say anything. A  consideration to take into account. In essence we are not authoritative

 M.

[Reza Sharifi]

The PSUs are hot-swappable. So, you can simply add a second PSU to each switch while they are running, and connect them to the proper power source. 

That said, I would still do it in a maintenance window just in case something goes wrong.

HTH