PSU intake project

[Rinaun]

Hi guys,


I've been running my 750w XFX psu (green fan model) since 2010. In the past I've had to re-oil the fan bearings as they get noisy, but this time I decided to replace the fan so I don't have to keep doing this every month. When I replaced the fan with a 12v .35A brushless 120mm fan, I noticed the PSU will spin the fan initially on boot, but won't spin it after that. I'm not sure if it's because it's being adequately cooled, or if the very low amps/volts the fan controller is sending the new fan is simply too low. I tried looking up this model, but couldn't find any reliable information regarding its fan controller.

My alternative is to use the pre-existing fan above it, and only use it. This is what my current PSU cooling setup looks like:

My question is this: With the top fan pulling around 50-70cfm of air 24/7, and the PSU pulling clean air from outside, should I be worried about the PSU fan not working? I mean, the radiator fan is less than 20mm apart from the non-spinning PSU fan. I really don't want to take the PSU back out (very custom rig), so just leaving the fan in there and hoping it works when the PSU gets a bit warmer and sends more volts/amps to the fan is my ideal outcome.

I'm not sure why the fan spins just for half a second, then never spins again. I haven't load-tested it too much but I really don't want to replace the fan again/buy another PSU.

Let me know what you guys think! I take care of this stuff 9/10 but Ifigured I should get some peer review before I just leave it be until next rebuild (2014). I also want to mention I clean this PC every month, so the PSU building up dust isn't an issue

 

[denis280]

The psu fan not working is not to good.first of all. it's stopping airflow.and you will damage that psu.

 

[dma0991]

It could be that fan needs a higher start voltage. Check the make and model of the fan; the closer the specs of the replacement fan to the original(the round sticker on the fan should provide this information), its more likely to work.

I wouldn't mount my PSU that close to the radiator, especially with it facing towards the radiator. Its a disaster waiting to happen if there is possibility of the radiator puncturing causing a coolant leak into the PSU and shorting it out.

 

[Saylick]

I personally don't have any experience with replacing PSU fans, but I wouldn't want to risk jeopardizing the PSU in any way considering it's what keeps the rest of the system fed. I've never had a PSU fail on me before, nor do I want it to occur, but I've only heard bad things whenever people skimp out on their PSU and it fails.

The fan inside the PSU should ramp up whenever the PSU internals get hot. In your situation, you only have the rad fan cooling the internals and will not ramp up if your PSU gets too hot. This is a bad moment waiting to happen imo. Therefore, I highly recommend fixing that PSU fan.

 

[DavidT99]

From the airflow diagram I assume you have installed the PSU fan back to front as normally the PSU fan is an intake. IMO this is bad news as you will be sucking in unfiltered dust which will eventually cover the PSU internals and cause a malfunction.

David

 

[Rinaun]

Damnit, I totally don't want to take this power supply out again but it sounds like that's what is going to happen. It was a nightmare getting it out and I had to use the dremel to cut a 5" piece of aluminum out in order to install the new fan, as well as take half the computer apart. I'm not worried about the radiator ever getting punctured because its not in a consumer environment (it's in a server cage on a shelf).

It could be that fan needs a higher start voltage.

I hope you aren't right!

I'm going to bet the amperage if anything is causing the issue, but I tested this fan and while it's not suggested, it ran fine overamped. The only reason I used this non-spec fan is because it's all I have that will fit and ordering another one will cost money and take time that I don't have ATM.

I'm wondering if the fan controller is very specific and is simply ignoring the fan because it sees its under limit (somehow). Regardless, thanks for pointing this out and making me rethink things. I should of rubber duck'd and found this out on my own, but I guess you guys don't mind pointing out logical flaws

From the airflow diagram I assume you have installed the PSU fan back to front as normally the PSU fan is an intake. IMO this is bad news as you will be sucking in unfiltered dust which will eventually cover the PSU internals and cause a malfunction.
David

Thanks David for your concern . The machine gets cleaned on a bi-weekly basis, so keeping the radiators/PSU clean isn't an issue. It's mandatory cleaning anyways so I highly doubt it will be skipped anytime soon. Also, I noticed that hardly any dust ever builds up in the PSU, but everything below the video card gets dusty real quick. I'm glad I don't have a bottom-mounted PSU!

I'm going to avoid gaming until I pick up an appropriate 120mm fan. For those concerned about airflow: I have a digital infrared temp gun, and even doing MILD gaming the PSU with the fan disabled doesn't get that hot. When the fan DID work, I never heard/saw it spin fast at all. You need to remember that the PSU on this rig is ducted straight into a 60CFM radiator fan. Most PSUs don't even need a constant 60CFM of airflow. I understand it's a terrible design cooling-wise, but most of the equipment I'm using on this project is third-hand, fixed defective parts, and some must be installed in certain places for math and other cooling reasons. For example, the radiator must go there because of a self-bleed system and PSU can't be faced downwards due to hosing/ball valves in the way (4-6 lines).

If I had to redo it all I'd of simply bought a bigger case instead of sticking it all on the outside/making the PSU inaccessible When I finish fixing it I'll take a few pics; it's a total Frankenstein of a custom WC loop.


edit: http://www.newegg.com/Product/Produc...82E16835103090 I'm almost positive this will work.......right? This fan is rated at 12VDC/0.35A, while the stock fan is 12VDC/0.33A. Cheapest long-life fan I could find locally with higher amperage.

 

[dma0991]

I hope you aren't right!

I have four fans, two Noiseblocker XLP and two Noctua NF-P12 connected to Lamptron FC5v2(has voltage readouts). My observation of tweaking the input voltage to its lowest is that there is a minimum required to allow it to start. For example, if my fan started spinning at 6V, once it starts spinning for a few seconds, I could reduce the voltage much lower to 4V. But if the fan stops spinning(shutdown, etc), it will not spin when I turn on the PC again till I meet that required minimum start up voltage.

Most manufacturers do not advertise start up voltage, but you can refer to this chart showing some fans and their start voltage. Another indicator of a low start voltage fans are low RPM ones, but it isn't an accurate indicator as it is highly dependent on the quality and design of the motor.

 

[Rinaun]

Bought the fan. Still doesn't work! This fan is rated ABOVE what the ADDA is listed at. I ended up just plugging the fan straight into the PSU and running it that way. I'm not sure if the PSU can be fixed correctly without an exact replacement fan, and I'm not willing to buy another fan only for it to fail. I'll just ride this PSU out (with the fan powered externally 100%) until I rebuild or it dies.

 

[denis280]

I'll just ride this PSU out until I rebuild or it dies.

Don't take a chance with that psu.

 

[Rinaun]

Don't take a chance with that psu.

I'll let you know if it dies and I'll let you say I told you so when it does. I did an hour of BF3 and while my radiators got hot as normal the PSU was still way under thermal requirements. The only thing that will stop me from using this PSU is if it no longer works, or someone offers me a better PSU (hopefully a x750 seasonic). I'd rather figure out why the fan is acting up.

edit: played 3-4+ hours of BF3 in one sitting at 80c room temp. No issues so far