Quote from: Thedarkside1 on February 13, 2018, 05:20:25 AM

Hello. I'm looking to add a second power supply to my rig. I currently have 1 psu powering everything (mobo, ssd, cpu, 3 gpus, 3 risers). I just got a 4th gpu and looking to connect it to second psu (first psu doesn't have enough connectors). I will also need Add2psu to turn on/off both psu at the same time

So do you think it's ok to just connect a gpu and a riser only on second power supply?

Basic guidelines with multi-PSU rigs:
Use one PSU to power the board's main connection (dual PSU cables shouldn't wire all the connections from both 20/24-pin main connectors; it should only have all the cables for one connector, then the other should only have the green pin and one ground connected). Use this same PSU to power the 4/8-pin CPU connection(s) on the motherboard. Generally this PSU should also be used to power the storage device, but that is not necessarily a requirement. Ensure that the other PSU only deals with graphics cards and risers.

Ensure that you distribute the load such that neither one of the PSUs is over 70-80% of its rating. Despite the "Add2PSU" name, you're not truly getting the effects of a single PSU; appropriate load distribution remains your responsibility.

If you're like me and choose not to use an Add2PSU device or dual PSU cable, ensure that the secondary PSU is powered on before hitting the boot switch to turn on the primary (connected to the motherboard) PSU.

As always, but especially in this case, use quality PSUs. Adding more PSUs in a nonredundant configuration, as is typical, can add more points of failure. For example, if EITHER unit fails, it may result in downtime for the entire rig. (If the primary PSU fails, this is the obvious result. However, if the secondary PSU were to fail, it may or may not be the case that the rig can continue mining with the graphics cards connected to the primary PSU. Oftentimes, a power failure to some of the cards can cause the mining software/drivers/OS to throw an error, downing the entire system.)
Using quality PSUs is especially important when each represents its own possible point of failure for your rig. Look for quality OEMs such as Seasonic, FSP, and Superflower. (HEC, CWT, Sirfa/Sirtec are definitely lower on the totem pole, but better than no-name units. I personally don't use these for mining rigs, where the are under heavy loads 24/7, but I've used their units for home use and they usually do the job.)