One fan Sonata

Tom Brown · Post by **Tom Brown** » Thu Jul 28, 2005 2:16 pm

This afternoon, I tried an experiment. It didn't work out but some of you may find it interesting.

I run a 90um Athlon64 at 1.2 volts with an XP-120 heat sink. It doesn't need a fan. My video card and chipset coolers are passive also.

... so I removed the 120mm case fan, taped it up, removed the 80mm PSU fan and left the 80mm hole. Then I installed a single 120mm fan in front of the drive bays. That fan is connected to a Rheobus. The Antec holes are taped up too.

It actually works pretty good. The HD, CPU, and system board stay plenty cool. My ambient is 27C and the temps were HD=35, MB=36, CPU=31. Note: the system was idling and not under load.

Oh yeah... I also underclock lightly.

The problem is that a plenum thermometer in the exhaust hole of the PSU reveals a temperature of 110F. The highest I've ever seen it before this experiment was 100F.

Also, using a piece of tissue, it's clear that there is less air going through the PSU than a Panaflo 80L would produce at low voltage.

I only ran the system for about 20 minutes with this configuration. I'm pretty sure the problem is the way the fan mounts to the drive cage. I've got all but two of those air slots taped off. The back of the fan is mostly blocked.

It would be better if the fan were on the front of the chasis, like the 3700amb. I'm pretty sure a single fan would cool a low power system in a 3700amb but then the fan would be right out front and that would negate some of the gains. I'm going to try a cardboard duct to see if I can improve the airflow.

I thought some of you might find this experiment interesting. I'd love to run a single 120mm fan inside the machine, if I can get away with it. ... not that it was loud before but now it's silent even when I listen closely.

Bluefront · Post by **Bluefront** » Thu Jul 28, 2005 2:58 pm

It is possible to run on one fan, but you have to make certain all the airflow is used to the max. A 120mm fan running at 1500rpms should be sufficient.

You report high PSU temps with your setup. It is quite likely with your positive pressure case, you have airflow getting out of the case, by-passing the PSU ecscape opening.

Openings around the I/O ports on the board, and openings around the card slots are a usual suspect. For your setup to work ok, everything must be sealed tightly.

shades_of_blue · Post by **shades_of_blue** » Thu Jul 28, 2005 5:55 pm

why not just get a pair of nexus 120s or yateloon d12sls and run them around 500-600rpm?

with a pair of d12sls running around 800rpm my power supply is equal to and/or louder than the case fans, no noticeable gain in system noise. the hdds are a much larger contributor of noise IMO, at least in my system.

scruzbeachbum · Post by **scruzbeachbum** » Fri Jul 29, 2005 7:42 am

110F is only 43C. You are worried about a 7C rise in temp from the PSU?

(PSU outflow temp - mobo temp = 43C- 37C)

Bluefront · Post by **Bluefront** » Fri Jul 29, 2005 7:56 am

As a reference point....My one-fan setup similar to what Tom Brown posted, has a PSU output temp about 36C-40C depending on ambient temps and usage.

This is with a P4-2.66, using a cheap !20mm fan from CompUSA @ about 1400rpms, 28C ambient.

One-fan computers rule.....

frostedflakes · Post by **frostedflakes** » Fri Jul 29, 2005 8:32 pm

I agree, 43*C does not seem like anything to be overly concerned about.

Also, for a single-fan solution, I think an exhaust fan would be must more helpful than an intake fan.

I am also running a single-fan setup, but most of my components are low-power/laptop parts, so keeping the computer cool isn't too difficult.

scruzbeachbum · Post by **scruzbeachbum** » Sat Jul 30, 2005 7:08 am

By the way, I'm running just one chassis fan - as rear exhaust. Here's what Everest has to say at idle:

Sensor Properties:
Sensor Type Winbond W83627HF (ISA 290h)
GPU Sensor Type Driver (NV-DRV)
Motherboard Name Abit NF7 Series

Temperatures:
Motherboard 32 °C (90 °F)
CPU 54 °C (129 °F)
GPU 58 °C (136 °F)
SAMSUNG SP1614C 29 °C (84 °F)

Cooling Fans:
CPU 1197 RPM
Power Supply 1406 RPM

Voltage Values:
CPU Core 1.63 V
+3.3 V 3.25 V
+5 V 4.95 V
+12 V 11.86 V
-12 V -11.95 V
-5 V -5.00 V
+5 V Standby 4.97 V
3.3V Dual 3.50 V
DIMM 2.61 V

Bluefront · Post by **Bluefront** » Sat Jul 30, 2005 9:17 am

Heh....it's a whole new ball-game when you are using a chassis fan and a PSU fan. That setup is rather easy.

When you're running the whole computer off one fan, you find a bunch of problems you never knew about....

scruzbeachbum · Post by **scruzbeachbum** » Sat Jul 30, 2005 6:42 pm

I bet.

Tom Brown · Post by **Tom Brown** » Tue Aug 02, 2005 8:49 am

It's summer and I've been spending a lot of time at the lake. I like to turn the A/C off when I'm out of town and the temperature really climbs up so I'm not going to try the single fan configuration again until fall. Until then, I will run a two fan setup.

I'm confident it's doable. Thanks for the suggestions.

- Tom

timmytimmytimmy · Post by **timmytimmytimmy** » Tue Aug 02, 2005 10:41 pm

While I can't lay claim to having a one-fan system, I have 2 fans. One on the CPU heatsink, and the rear 120mm fan acts as an intake. As a result, warm air comes out the front, which is nice for warming my hands. My system remains relatively cool, I have undervolted my CPU.