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  1. #1
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    Fans and airflow - what's your take on things

    From the other thread - my PC bits turned-up today and the case (a Zalman Z3-TF) seems nice for a cheap (in this case technically 'free') case and so I used it in favour of the cheap-chinese finger-slasher the existing bits were in - BUT

    What's your take on the direction of PSUs in bottom-mount cases?

    A Google suggests it's entirely 'personal preference' - assuming there's a grille - and there's one on this case so I went for 'fan down'. The fact the GPU fan is only 3-4" away from it would only mean the PSU pulling air away from the GPU if I inverted it - but we'll have to see if that works I guess?

    Next-up case cooling. There's a fan grille next to the CPU and a fan was included BUT

    a - the header is tight between the the CPU and GPU so there's not many options for routing it without it catching in the CPU fan
    b - it was installed 'pushing air out' but as it's next to the CPU (the fan for which pulls air IN) that's not wise IMO?

    What's your take on case cooling - do you want to pull air in or push air out?

    I have a nice quiet 120mm which will fit on the door - that way it's drawing air in directly above the CPU (and SSD/HDDs too) so I suspect leaving the rear grille clear (e.g. removing the other fan) will exhaust excess heat without fan assistance (at least that's what I'm testing!!)

    It's sitting here now on test - temps are stone cold - it's quiet too - advice would be nice before I hand-it-over tomorrow tho!

  2. #2
    Secondary Hivemind Nexus Jesus_Phish's Avatar
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    You want to pull air in and push air out.
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  3. #3
    Network Hub BobbyFizz's Avatar
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    Always pull air in, quite simply you want to create more pressure in the case so it pushes out the hot air and cycles more cooler air in.

  4. #4
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    Quote Originally Posted by Jesus_Phish View Post
    You want to pull air in and push air out.
    Quote Originally Posted by BobbyFizz View Post
    Always pull air in, quite simply you want to create more pressure in the case so it pushes out the hot air and cycles more cooler air in.
    This. Unless someone can offer proof of a better alternative?

  5. #5
    Secondary Hivemind Nexus Boris's Avatar
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    Generally you have to decide if you want positive pressure (sucking in more than you're blowing out) or negative pressure (blowing more out than you're sucking in).

    Positive pressure keeps dust from being sucked into the case through every nook and cranny (especially if you have dust filters on the intake fans), but is more noisy.

    I personally like negative pressure, but I open up my PC once a year and take out all the dust. I would not remove the rear fan. The heat will build up inside the case. Use a zip tie or tape to route the cable away from any fan blades.

  6. #6
    Secondary Hivemind Nexus Heliocentric's Avatar
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    It's about surface transmission. Ducting and low speed fans in are great for focused cooling, and a nice low speed fan drawing out gives and evenly distributed draw over ambient components.
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  7. #7
    Network Hub Ernesto's Avatar
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    I think, every consumer PC component is practically fool proof (regarding temperature). You are not building a satellite. Just a PC. Plug your components (with the stock cooler) in some case and don't worry about temperature. As long as there are some holes in the case, you'll be fine.

    On the other hand: It's just fun to tinker with fans and ducts and optimizing stuff. Besides: A huge cooler looks badass. In 90% it's probably the reason to buy a 'better' one ;D

    I have it like this: Air comes in from the front with a 120 mm fan and another one pushes it out of the back, together with the PSU fan on the bottom. There's a ton of additional grilles on the top and the side but I don't see any advantage in using those.

    And with a 'negative pressure' you surely mean a negative pressure difference. Because there is no such thing as a negative pressure.

    Cheers!

  8. #8
    Secondary Hivemind Nexus Sakkura's Avatar
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    Quote Originally Posted by trjp View Post
    What's your take on the direction of PSUs in bottom-mount cases?

    What's your take on case cooling - do you want to pull air in or push air out?
    The PSU should be installed so it pulls in air from below and exhausts it out the back.

    Case cooling should have both intake and exhaust fans. If you pick only one or the other, exhaust fans are better for cooling but intake fans are better for dust management (assuming the intakes have dust filters). Balanced pressure brings the best cooling performance, negative pressure is close behind but sucks in dust, positive pressure has the worst cooling performance but is the best at getting rid of dust.

  9. #9
    Network Hub spacein_vader's Avatar
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    Quote Originally Posted by Ernesto View Post
    On the other hand: It's just fun to tinker with fans and ducts and optimizing stuff. Besides: A huge cooler looks badass. In 90% it's probably the reason to buy a 'better' one ;D
    I disagree, only people with a windowed case would do it for that reason. The main two reasons are overclocking and noise. Although less of a problem now due to more efficient processors and improved cooler design, stock HSFs used to be very marginal on cooling performance, culminating with the infamous Prescott P4 series that produced so much heat the HSF couldn't cope so the processor permanently throttled back to reduce overheating. These days that's less of an issue and you can usually get at least a mild O/C from the stock set, but for people who want to push it further an aftermarket cooler is the only option. Stock HSFs usually use cheap, high rotation fans that make a lot of noise. Aftermarket coolers can afford to use lower RPM fans due to their generally greater surface area, thus reducing noise.

  10. #10
    Network Hub Ernesto's Avatar
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    Quote Originally Posted by spacein_vader View Post
    I disagree, only people with a windowed case would do it for that reason. The main two reasons are overclocking and noise. Although less of a problem now due to more efficient processors and improved cooler design, stock HSFs used to be very marginal on cooling performance, culminating with the infamous Prescott P4 series that produced so much heat the HSF couldn't cope so the processor permanently throttled back to reduce overheating. These days that's less of an issue and you can usually get at least a mild O/C from the stock set, but for people who want to push it further an aftermarket cooler is the only option. Stock HSFs usually use cheap, high rotation fans that make a lot of noise. Aftermarket coolers can afford to use lower RPM fans due to their generally greater surface area, thus reducing noise.
    Well, that's what I mean. Kind of. What you described is what a small fraction of enthusiastic PC users does. The other 90% buy it because it's shiny.
    Look at the design of these things. Granted, most of the aftermarket coolers work better then the stock ones (which is hardly an achievement since they sell it for double the price or so), but they put a bigger emphasis on looks. To me that says something about the target group.

  11. #11
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    I was planning to put a non-stock cooler for quietness (that and I have 2/3 of them doing nothing) in but as the thing came ready-assembled I thought "ah - why bother..."

    Since I went into the BIOS (not easy, it doesn't recognise my USB keyboard so I had to dig-up a PS2 keyboard!!) and set 'Silent' on Case and CPU fans - it's been pretty-much that.

    The CPU is sitting at 28degrees which is WAY cooler than my old desktop ever got too - the owner didn't come for it today tho so I'm going to play some games on it ;0

  12. #12
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    By way of an update, my mate, having run that PC, was complaining about noise.

    I'd gone with PSU 'Fan Down', Large Side-panel Intake Fan (over CPU), stock cooler and no outlet fan (as it's cable-run was a pain-in-the-ass/fouled the CPU fan)

    Took me a while to realise it was the PSU fan which was noisiest but short of a new PSU I couldn't see a solution. With no other options, I installed an exhaust fan via a molex-7v adaptor (so it runs slowly and quietly) - cable-tied the cable out of the way and VOILA - the PSU fan isn't joining-in now.

    Seems the case was holding enough heat to trigger the PSU's fan threshold (around 45 degrees in the internal temp sensor). Once the exhaust fan was working, it dropped the internal temp closer to 40 - PSU fan doesn't wind-up - PC is MUCH MUCH quieter.

    Moreover, I disabled the side-panel intake fan to see what happened and it made NO difference - system runs identical temps - cools down as fast after you close a game - so that's coming out - and I'm leaving the exhaust fan on a constant speed rather than on the system controlled header because I think a constant slow/quiet fan is better than one which is changing speed all-the-damned-time ;0
    Last edited by trjp; 22-02-2014 at 05:17 AM.

  13. #13
    Both in and out. Just try to pull it out from a higher point than you put it in, and try to make sure the only "out" points are ones where you'll actually have hot air coming through. Don't make an air corridor that goes from an "in" source over non-components and out the back.

    For instance, on my current case, I've got an "in" fan on the bottom front and the "out" fan below the PSU in the middle back. Ignoring some bad design in the case, this is ideal. First, the intake is low, so you get the coolest air you can in the room. Second, the outtake is high, so the hot air will naturally rise to it anyway. Third, the air corridor crosses the motherboard and the GPU, sucking out whatever ambient GPU heat (a major heat source) that the on-card cooling solution doesn't get or leaks out.

    Also, preferably have a way for the CPU heatsink to blow straight out the side of the case, even if you need a funnel-type thing to trap that airflow. That way it's not getting blown around the motherboard on its way out.

  14. #14
    Network Hub spacein_vader's Avatar
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    Quote Originally Posted by Talksintext View Post
    Both in and out. Just try to pull it out from a higher point than you put it in, and try to make sure the only "out" points are ones where you'll actually have hot air coming through. Don't make an air corridor that goes from an "in" source over non-components and out the back.

    For instance, on my current case, I've got an "in" fan on the bottom front and the "out" fan below the PSU in the middle back. Ignoring some bad design in the case, this is ideal. First, the intake is low, so you get the coolest air you can in the room. Second, the outtake is high, so the hot air will naturally rise to it anyway. Third, the air corridor crosses the motherboard and the GPU, sucking out whatever ambient GPU heat (a major heat source) that the on-card cooling solution doesn't get or leaks out.

    Also, preferably have a way for the CPU heatsink to blow straight out the side of the case, even if you need a funnel-type thing to trap that airflow. That way it's not getting blown around the motherboard on its way out.
    This. In low, out high is a good move. Also side mounted 'blow hole' fans have been unnecessary since the end of the P4 'space heater chip' era. They usually cause more noise from case resonance and make no difference to cooling performance.

  15. #15
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    I stared at the 'front panel' fan location to install the old side-panl-fan - but it's SO CLOSE to the HDDs that installing a fan looked a PITA and a half

    I'm in the mood for trouble tho, so I pulled off the front panel and screwed-it-in-there and - amazingly - it fits OK and cables don't snag it, although it will have to be removed to get the 2nd HDD out again ;0

    Hey ho

  16. #16
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    Always curious that a GPU is always facing "down". Thus blowing air to the bottom and in most cases now, into the PSU which is shooting air "up".

    I have a Antect 900 and 1200. 2-3 front fans that blow air over the HDD bays. GPU down. PSU in bottom blowing air up. Optional side opening on the case door panel (have no fan there). CPU fan. Then the traditional rear fan along with a giant fan on the top pushing air out.

    The most trouble I have is finding the best place to tape the power cords so they not in the way of each other and running into fans. Oh and a couple of failing fans on the 900 that need to get replaced. Noisy right now.

  17. #17
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    All the decent cases I've used recently had a both an intake and exhaust for the PSU. Why have extra warm air going into the case when you don't need to?

  18. #18
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    It has an outer exhaust, but do not think PSU ever had a fan pushing it that way due to the small size. Top loaded PSU would fan down but be right next to the rear fan to fan out the heat.

    The newer PSUs also delay using the fan until under high load.

  19. #19
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    This PSU does that - and since I reconfigured it I've never heard it's fan (and you can't miss it - it's not quiet!!)

    You're also right about the GPU cooling thing too - even with a low-front-fan sucking air in, the GPU runs hotter in this case than it did in the older (larger) one. If you used the spare PCI slot on this PC, there would be NO air getting to the GPU at all!

  20. #20
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    Quote Originally Posted by Moraven View Post
    It has an outer exhaust, but do not think PSU ever had a fan pushing it that way due to the small size. Top loaded PSU would fan down but be right next to the rear fan to fan out the heat.

    The newer PSUs also delay using the fan until under high load.
    Thought the spare I have was dead because of this, then the fan kicked up. Looks like I was not even pushing it close to it's rating. :P
    It is a technical difference, but's there none the less.

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