Does the fan go on the bottom or top of the power supply?

The Corsair TX750 PSU has a thermally controlled 140mm fan on "the top".

The review pictures show that the PSU has a standard rear-exhaust air-flow planned.
But, with a single fan (at the "top").
In most cases the Chassis has a PSU placement at the top (link to example picture).
If that is your placement picture, the "top" of the PSU should be facing down.
However, if your cabinet expects a PSU at the bottom, the fan should face upwards.

alt text -- rear facing side of the PSU

alt text -- "top" side, should face inwards,
towards the motherboard/processor.

The fan will create an airflow leading from inside the cabinet and out the rear grill.

  • There should already be another outlet fan positioned under the PSU location on the Chassis
    • This will create another flow away from the processor
  • Additionally the processor fan will push "on-to" the processor itself
  • Would be good if you can manage a small grill on one side of the chassis
    • somewhere "above" the the processor fan, to allow it a good source of fresh air
  • This would leave just your graphics card fan path
    • That is usually facing the processor and chassis fans
    • The air flow from its fan (if any) is pulled out by the chassis fan
    • If things are not right here, its air-flow could land up on the processor leading to bad thermal additions to the processor.
    • But, usually these things are managed by manufacturers of various parts (chassis, motherboard, etc)

When you start playing with ideas of repositioning things in your chassis,
It is expected you know better than these generalized designs,
and are planning a more customized thermal solution for your assembly.

As a aside, the review has the following conclusion (with warnings).

The Corsair TX750W is fitted with a clear plastic fan baffle that covers approximately fifty percent of the total fan area and I have to ask, is it really needed? The reason for its inclusion must be to improve cooling but I couldn't help but notice a quite powerful airstream leaving the fan in the area of the baffle. This isn't the first time I've seen the baffle fitted so just out of interest I removed it and ran the power supply at full load for over two hours and the only difference I observed was a reduction in fan noise, temperature difference was negligable. This is just an observation and I don't advise anybody attempting to remove or run the power supply without the baffle, the designers must have their reasons for its inclusion, even if I can't find it!

Unless you are an overclocker or heavy-user, such things should not matter.
Corsair PSUs are well built and do not need any tempering.

Update based on the Antec P183 Chassis.
From the Antec site notes on P183.

  • Dual chamber design isolates heat and noise: the power supply resides in a separate chamber to isolate heat and reduce system noise
  • No power supply included
  • Power supply option: comes with a power supply mounting adapter to mount either a standard size power supply or Antec's exclusive CP Series power supply
  • Innovative three-layer, sound-deadening side panels and front door (aluminum, plastic, aluminum) dampen noise and ensure Quiet Computing™

I am going to refer pictures from this review I found (that also looks interesting).

  • This is an "advanced" mid-range case with 2 fans separated from the PSU system and an optional 3rd fan on the front panel (and two more on the front panel if you will)

  • Which means, the case manufacturer has already done some amount of customization for you

  • The PSU fan facing down, will correctly pull in air from the upper chamber to keep a negative pressure there

  • Probably the front panel fan will help get a fresh-air flow towards the PSU intake too
  • The PSU rear out-flow will be a good thermal exit for it

Quite neat.

  • If the case was not designed with a barrier between the PSU and the motherboard complex,
    I might have suggested an upward facing fan position
  • as it stands, with the P183, a downward facing fan with the Corsair TX750 inverted sounds good
  • Since you are working with this case, I would also suggest reading through
    • the review article I link here, and
    • the Antec page notes for the P183 case
  • Regarding the other chassis fan I expected to be below the PSU in my earlier notes,
    That is complemented with a pair of 120mm fans setup on the rear-top of the P183.
    Most of the other notes on thermal paths get differently handled with P183 (it is customized)

Your power supply should only install one way in the case. Usually it is at the bottom when the power supply is at the top of the case. But I have seen the power supply mounted at the bottom of the case with the fan pointing up. Generally it points towards the CPU.

Hopefully you haven't removed the fan from the power supply and are now trying to put it back together.


To put it succinctly, the fan is never against a panel of your chassis and therefore points inwards, usually towards the CPU.

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