Hello, what Young means is that when hot spare is enabled if the load on the active power supply is more then 50%, then the redundant PSU is switched to active state. If it below 20% it switch to the sleep state.  Also mixing PSUs from previous generations of servers can result in a PSU mismatch or failure to power on. BTW if you already replaced PSU in the same position and it didn't solve it, it should be an issue with the PDB (power distribution board) or the motherboard, I don't see any other test to do. Thanks Marco  
T430 with dual PSUs. A few weeks ago, the system indicated PSU2 problem/failure. Contacted by the on-site personnel, and site unseen, I used the system's original order configuration sheet, procured a replacement (OEM) PSU. A team member on-site inserted the new PSU (#2) and get green lights for both. I walked him through (via phone) the process to reset the iDRAC logs and the LCD is no longer amber. Confirmed Power Cap Policy shows an error -- SWC0242 (A required license is missing or expired) and is set to Enabled. I get nothing much for "hits" regarding this message...so I continue with troubleshooting. Can confirm Power Supply Options is configured as "Input power Redundancy". Again, both PSUs light up green. Power on and boot up without a problem. Unplug PSU1 and the system shuts off immediately. Swap PSUs, reset log (PSU2 is not configured correctly) and try again, the system shuts off immediately. After trying many combinations of this arrangement, the input power is good (with or without inline UPS), the power cords are good and all 3 PSUs (2 original and 1 new) are good...as long as they are in slot #1. Double-checked System Setup and confirm "Input Power Redundancy" is selected. Other than Power Cap Policy (the one with this SWC0242 error), all other options are grayed out. Reseated all connections from the PSU board to the motherboard, same result. Again, both PSUs light up solid green on the back-end. With only a PSU in slot #2, the server will not power on. With the server off, and tethered to the UPS, the UPS registers 86W on PSU1 and 4W on PSU2. What would cause a PSU to register such low wattage when attached to slot #2 (vs #1)? Unsure what else to try/attempt before considering a change to the PSU board, motherboard or my career.  :0)
T430 PSU Problems