Combine 2 PSUs for GPU

[kerrat]

Hello and thanks for reading!

I want to build a very slim desktop computer and want to use two flex ATX 1U 400W server PSUs, same model, for this. I can't use a normal consumer PSU as it would be too heigh and I need 750W+ to power:

Ryzen 7 2700X (105W),
RX580 PowerColor GoldenSample 8GB (600W),
some hard drive (8W),
and want to use a Gigabyte GA-AX370M-Gaming 3 AMD X370 Mainboard.

I already read about using two PSUs semi-combined (on PSU only connetced to the other with the wires to turn on) in which one PSU powered the GPU and the other one the mainboard and everything else. Of course not an option for a GPU hungrier than the PSU.

Is there a way to combine the two ATX server PSUs to power the GPU or everything else combined?
There is a thing floating around called Add2PSU which just seems to be a molex-adapter with a relay, probably nothing I could use?

 

[asoroka]

Not really a good idea, you have to worry about floating earth issues.

What case are you planning on using?

What about something like
FSP 600w 80Plus Platinum IPC-2U
Watts: 600 W

Dimension: 260 X 100 X 70 (mm)

Note that the smaller the case, the harder it is to maintain good airflow.

 

[Phillip Corcoran]

Get an ATX form factor case that is micro-ATX compatible, then you have a wide choice of standard ATX PSUs to choose from. Much better for keeping the system cool as well (important if, as I assume, you'll be using this rig for gaming judging by your choice of GPU).

Only other option if you insist that the case has to be slim is to use a less demanding GPU, which will obviously reduce the rigs gaming performance.

 

[kerrat]

Not really a good idea, you have to worry about floating earth issues.

What case are you planning on using?

What about something like
FSP 600w 80Plus Platinum IPC-2U
Watts: 600 W

Dimension: 260 X 100 X 70 (mm)

Note that the smaller the case, the harder it is to maintain good airflow.

Isnt it possible to ground them both? Or are there other problems which could occur besides that?

As for the case, I am building my own as I've got some experience with metalworking - of course I would ground that, too.

I try to integrate this build into my living space and have a lot of space in width and length but only 4-4.5 cm in height. I thought a lot about cooling, tested a few ideas with other components and don't have to worry about this anymore. The only thing left to solve is the PSU. I can't "outsource" it to somewhere with more height and server PSUs that are slim enough seem to be my only option.

 

[USAFRet]

A "server" PSU is going to be quite noisy. Smaller fans have to try to move the same amount of air.
Faster RPM = noise.

And trying to combine 2? Bad idea.

 

[kerrat]

A "server" PSU is going to be quite noisy. Smaller fans have to try to move the same amount of air.
Faster RPM = noise.

And trying to combine 2? Bad idea.

Setting heat, noise, aesthetics, all of these things aside: what is the wiring I would need to do? Are there any electronic problems that may occur? Some need for a over-voltage protection? Is one PSU going to send power into the other?

 

[USAFRet]

Why not just buy a single 1U server size PSU that can run the whole thing?

https://www.newegg.com/Product/ProductList.aspx?Description=1U%20server%20power%20supply&Submit=ENE

 

[asoroka]

as long as you can take care of the floating ground then ther will not be any electrical issues.

I would still advise you to use a regular atx power supply, it will only be 86mm high.

You need at least that much clearance for your CPU heatsink anyway.

 

[kerrat]

Why not just buy a single 1U server size PSU that can run the whole thing?

https://www.newegg.com/Product/ProductList.aspx?Description=1U%20server%20power%20supply&Submit=ENE

Getting a server PSU with 750+ Watts would be much more expensive, combining two PSUs would be much cheaper. I will take your advice if it wouldnt work!

as long as you can take care of the floating ground then ther will not be any electrical issues.

I would still advise you to use a regular atx power supply, it will only be 86mm high.

You need at least that much clearance for your CPU heatsink anyway.

Thank you a lot! Would there be an issue if the PSUs would be turned on with a delay? Not that I really plan to, just to make sure

 

[asoroka]

Not sure what you mean by delay.

you would need both PSU to come up at the same timeotherwise some devices may not be properly recognised.

 

[Wolfshadw]

Not sure where you're coming up with 600 watts for the GPU. Maybe recommended 600 watts, but that's for the entire system, not just the GPU. No consumer level GPU on the market today requires more than 375 watts (two 6+2pin connectors from the PSU). A quality 550 watt PSU should be more than adequate.

As for the size limitations, the problem you're likely to run into is that the "server" power supplies are unlikely to have the required PCIE power connectors to power your graphics card.

-Wolf sends

 

[kerrat]

Not sure what you mean by delay.

you would need both PSU to come up at the same timeotherwise some devices may not be properly recognised.

A lot of internet guides say its important to switch both PSUs on simultaneously (or not) for whatever reason, delaying would be switching one PSU on, waiting a few seconds or a minute and switching the second one on.
I didnt really understand why switching them on simultaneously or not would be relevant, so thank you!

Not sure where you're coming up with 600 watts for the GPU. Maybe recommended 600 watts, but that's for the entire system, not just the GPU. No consumer level GPU on the market today requires more than 375 watts (two 6+2pin connectors from the PSU). A quality 550 watt PSU should be more than adequate.

As for the size limitations, the problem you're likely to run into is that the "server" power supplies are unlikely to have the required PCIE power connectors to power your graphics card.

-Wolf sends

I looked it up on the PowerColor website, I kinda thought "Minimum System Power requirement (W): 600W" would be for the GPU, you seem to be right as a review of the GPU says it only consumes 290W or 340W in OC! That definitely makes things a lot easier as I could buy a cheap server GPU which would satisfy the power requirements, instead of combining two cheap ones.
As for the PCIE power connector, isnt it possible to use two molex for this? There seem to be adapters for this (the flex ATX I saw only seem to have 2-3 molex which really isnt a lot...)

 

[USAFRet]

Molex adapters to run a GPU are never a good idea, no matter what the PSU is.

There are 1U server size PSU's far in excess of the wattage you presumably need. No need to try to merge 2 smaller ones.
But that still doesn't help with the lack of proper connections for your desktop PC.

 

[kerrat]

Molex adapters to run a GPU are never a good idea, no matter what the PSU is.

There are 1U server size PSU's far in excess of the wattage you presumably need. No need to try to merge 2 smaller ones.
But that still doesn't help with the lack of proper connections for your desktop PC.

Is there anything that would help with this connector-problem, as molex adapters arent an option?

 

[USAFRet]

Molex adapters to run a GPU are never a good idea, no matter what the PSU is.

There are 1U server size PSU's far in excess of the wattage you presumably need. No need to try to merge 2 smaller ones.
But that still doesn't help with the lack of proper connections for your desktop PC.

Is there anything that would help with this connector-problem, as molex adapters arent an option?

Redesign your case to accept a regular ATX size PSU.
(that's what *I* would do, anyway)

 

[kerrat]

Molex adapters to run a GPU are never a good idea, no matter what the PSU is.

There are 1U server size PSU's far in excess of the wattage you presumably need. No need to try to merge 2 smaller ones.
But that still doesn't help with the lack of proper connections for your desktop PC.

Is there anything that would help with this connector-problem, as molex adapters arent an option?

Redesign your case to accept a regular ATX size PSU.
(that's what *I* would do, anyway)

I'll look for a way to properly connect a GPU to a 1U PSU or I'll really have to redesign.

You all have been incredibly helpful, thank you a lot! Honestly a much more productive forum experience than I expected!