Having issues getting 2x PSUs to work? 6 x VEGA 56

[knittycatkitty]

I'm having some issues having two PSUs run concurrently.

I have a few 6x RX VEGA 56 set up that is configured to mine Monero Cryptonightv7

The specs are
Intel Celeron
B250 motherboards (either BIOSTAR B250 BTC PRO or ASUS B250 MINING EXPERT)
COMeap Triple PSU adapter for BIOSTAR motherboard
8GB RAM
128GB SSD
6x VEGA 56
2x EVGA 750 GQ
PCIe risers v007 and v008s (connected via SATA or SATA to PCIe adapter)

APC AP7900 switched 30 amp 208V PDU
4 rigs per PDU

PPT tables
900MHz mem clock @ 900mv across the board (found it to be most stable and consistent)
1400MHz core clock @ 900mv across the board

Power consumption per rig singled out fluctuates between 4.5 amp to 5.3amps (translates to 936w to 1102w per 6-GPU rig) so I know for sure I'm well within the 80% efficiency mark, both per 750w PSU and for both 750w PSUs running

For just running 3x GPUs + main system (single 750w) it is consuming about 2.4amps (equivalent to 500w) so I know that the single 750w is also well below the 80% power consumption mark.


I had it running for a while just fine but I'm starting to notice that some of my PSUs are starting to either fail or the second PSU will shut down while mining 30 minutes in, this is consistent with almost 4 out of 8 machines. The main PSU will still keep chugging along just fine (although I would have to restart the system because 3 cards going offline all of a sudden is a big no-no for Windows)

I also have one special rig which has a 850w G3 and a 750w GQ as secondary and it is also experiencing the same issue (isolates the main PSU from extra heavy load issue if there is any as main PSU is 100w more)

I have extra brand new PSUs (all from different batches) and I am experiencing similar issues

If I switch the main and the second PSU, that second PSU powers the system and 3 cards just fine, and the main PSU shuts off after 30 mins.

I'm really confused whether my PSUs are failing or it's something to do with dual PSU setups I'm missing
I know out of 36 PSUs I have a good amount of defectives so I can rule that out.

Can someone fill me in?

[adaseb]

You sure that the PSUs are feeding current between each other?

Basically did you mix any of the +5V or +12V lines with both the PSUs somewhere.

If one PSU is +12.01V and another is +12.02V, then there will be current travelling from one to the other and you will blow up one of those PSUs.

[Bazzaar]

Have you got a power meter? such as a killawatt or similar.
Have you plugged the psus individually through it(but with the whole system running) to check the power each psu is drawing?
Sounds like you have from your post but I just want to be sure.
Like the previous post, I would check that you haven't got both psus plugged in to the same device somewhere.
Running for 30 minutes could suggest heat build up, is the air flow good?

Baz

[knittycatkitty]

Have you got a power meter? such as a killawatt or similar.
Have you plugged the psus individually through it(but with the whole system running) to check the power each psu is drawing?
Sounds like you have from your post but I just want to be sure.
Like the previous post, I would check that you haven't got both psus plugged in to the same device somewhere.
Running for 30 minutes could suggest heat build up, is the air flow good?

Baz

Yes I have, through my switched PDU
It has a GUI for this, indicates how much power each bank is using



Was able to calculate 2.4amps per main PSU  (500w)
and 2.1 amps on secondary (450w)

[knittycatkitty]

Seems it may just be defective PSUs as my other rigs are still up and running, I am running them through RMA. Will update here my progress


I'll probably move these PSUs to my Ethereum rigs and buy brand new 1300w or 1600w PSUs for these rigs so its just one singular PSU per Monero rig, minimum point of failure.

[yrk1957]

Try setting power to -20% or -30% in Overdrive for all cards.

[Mohondoa]

I am not familiar using 2 psu at my rigs. But consider my technician, he said you must check your current both of psu, maybe that 12v rails different current consumption. So it will be make your psu not balance, and it will blow.