Would dual PSUs run cooler and quieter? i.e. less stressed?

peterson · Post by **peterson** » Wed Jan 18, 2006 10:26 am

I'd like to know if it'd be a good enough idea to have 2 PSUs.
How would the rails be distributed?
How should the connections be distributed?

My case is if i should buy a new solitary PSU or complement my Nexus 4090 with let's say a Fortron 350W. It'd be a lot cheaper.

A small example. Would 2 300W run cooler than 1 600w if both are of roughly the same design.

Thanks.

Aris · Post by **Aris** » Wed Jan 18, 2006 10:34 am

you will most likely never use more than 400watts, and non SLI setups will most likely never use more than 300watts.

to answer your qestion, it would probably produce more heat to split power usage between 2 psu's than just using 1. if you look at most PSU effeciency results, the lower end (under 100watts) is almost always the least effecient aspect of their entire power curve. So instead of being right in the middle (best effeciency usually), your going to drop it down to a lower effeciency across 2 units, increasing overall heat output.

peterson · Post by **peterson** » Wed Jan 18, 2006 10:44 am

True, but 2 PSUs also will have twice the amount of cooling.
And if i'd use 2 less powerful ones, i may be closer to the sweetspot.

Or maybe not.

Devonavar · Post by **Devonavar** » Wed Jan 18, 2006 10:52 am

Lots of other people have had this idea before, and AFAIK no one has been able to deal with the practical problems. Do a search for Dual PSUs on these forums and you should come up with one or two good threads.

Fat_bloater_dave · Post by **Fat_bloater_dave** » Wed Jan 18, 2006 11:06 am

You could trying going for 2 Low power external PSUs that would help alot. Here is a PSU Wattage Calculator

Erssa · Post by **Erssa** » Wed Jan 18, 2006 11:07 am

Aris wrote:you will most likely never use more than 400watts, and non SLI setups will most likely never use more than 300watts.

to answer your qestion, it would probably produce more heat to split power usage between 2 psu's than just using 1. if you look at most PSU effeciency results, the lower end (under 100watts) is almost always the least effecient aspect of their entire power curve. So instead of being right in the middle (best effeciency usually), your going to drop it down to a lower effeciency across 2 units, increasing overall heat output.

Even with best efficiency the PSUs have usually ramped up their fans. In theory two PSUs would run with lower load, resulting in lower temps for individual PSUs (lower temps => lower rpm for fans, cool temperatures also result in better efficiency.)

Interesting idea, would be fun to know how it plays out in practice.

peterson · Post by **peterson** » Wed Jan 18, 2006 11:12 am

I think i have to try.
I'm considering a Fortron 350W or a Q-Technology 350W.
The 300W seems just a too old design.

qviri · Post by **qviri** » Wed Jan 18, 2006 11:20 am

Good luck wiring them up so that they both start when you press the power button.

I suppose you could keep one constantly running using a paperclip connection, but then whatever it's hooked up would get power constantly as well.

Right now, the most power hungry items are the CPU and the graphics card. Unless you have a card with an extra PCI-E power connector, you can only run both off one PSU. I'd be very careful half-powering a card (PCI-E connector on, but not from motherboard) as well... So you could pretty much only run optical and hard drives off the other PSU, which is not a big part of a modern system.

All this is unless you want to play with wire splicing and hooking up the main ATX connector to two different PSUs... But I'd be careful with that. Very careful.

peterson · Post by **peterson** » Wed Jan 18, 2006 11:45 am

Why can't i run the graphics card from the other PSU?
It's not a PCI-E but it has a separate molex connector.

qviri · Post by **qviri** » Wed Jan 18, 2006 11:48 am

Because despite having a separate molex, the card also draws power (IIRC, up to 70W) from the AGP slot.

You could do it if you can ensure that both PSUs will start delivering power at the same time (ie, splicing the ATX connector). Like I said, it's possible, but will involve a lot of work, and you have to be very careful.

peterson · Post by **peterson** » Wed Jan 18, 2006 12:02 pm

I have no intention of splicing the connectors.
I intend to use the connector that came with my Stacker case. I think it only connects the green cable. If it's necessary to splice the ATX connector, i'll pass.

It's little use to have a PSU only for a HDD, DVD and some other small stuff.

qviri · Post by **qviri** » Wed Jan 18, 2006 12:17 pm

Didn't know you had a dual-PSU ready case with a special connector. I suppose just the green wire would work. But then yeah, the second PSU would only power half (at best) of the video card and the drives. Not worth it IMHO, but whatever floats your vessel.