how "positive" must airflow be for a tower case to keep du..

Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

I'm upgrading a case (and the system inside it)? Actually two such
systems. I want to have positive air pressure in the case sufficient
to keep out dust. If you know this design, it has vents on the sides
of the case near the top, plus a row of vents in the back above the
adapter cards:

Both cases will have an ASUS A7M-w266 D,TBred 2000, no overclocking.

Power Supply is an Antec TruePower 550. (assume 0 cfm out at lowest
fan speed, 40 cfm at highest fan speed)

Cases are an Addtronics 7896A and a 6896A.

Assume roughly 140 cfm in. (2 120 mm Panaflow "L" model)

So, my question is:

How positive do I need to keep the case air pressure, to keep dust
out? That is, how much more should the cfm in be compared to the cfrm
out?
13 answers Last reply
More about positive airflow tower case
  1. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    In article <0m89g09l8i0g8fcq6e5eqhcq9ir5atusg8@4ax.com>,
    NOSPAMME@no-one-here.com wrote:

    > I'm upgrading a case (and the system inside it)? Actually two such
    > systems. I want to have positive air pressure in the case sufficient
    > to keep out dust. If you know this design, it has vents on the sides
    > of the case near the top, plus a row of vents in the back above the
    > adapter cards:
    >
    > Both cases will have an ASUS A7M-w266 D,TBred 2000, no overclocking.
    >
    > Power Supply is an Antec TruePower 550. (assume 0 cfm out at lowest
    > fan speed, 40 cfm at highest fan speed)
    >
    > Cases are an Addtronics 7896A and a 6896A.
    >
    > Assume roughly 140 cfm in. (2 120 mm Panaflow "L" model)
    >
    > So, my question is:
    >
    > How positive do I need to keep the case air pressure, to keep dust
    > out? That is, how much more should the cfm in be compared to the cfrm
    > out?

    I just tried "computer dust positive pressure" on altavista.com
    and one of the first hits was this.

    http://www.dustfreepcinfo.com/pages/184710/index.htm

    They use filters before their fans that pressurize the cabinet.
    Thus, clean air is used, and blowing that clean air under positive
    pressure, through any opening in the cabinet, prevents dust
    from entering.

    If your case blows dirty air in, I don't think it really matters
    what differential there is between "in" and "out". As long as there
    are dead spots in the case, where the air velocity is lower than it
    was originally, the particulate will settle out. (My thinking here,
    is that dust works on the same principle as silt in a river - as
    soon as the river widens and the water velocity drops, the silt
    falls out and collects on the bottom of the river.)

    To implement a solution like those dustfreepc people, you will
    need micron filters, a plenum, and your large 120mm fans. A plenum is
    simply a length of plumbing leading from the filter to the fan, and
    keeps the filter from getting too close to the fan blades. About
    3" of plenum between the filter and the fan should be good. You
    can try mounting the filter right on top of the fan, but you'll
    probably hear more noise coming from the fan that way.

    As soon as you use filters on a PC case, then you've got a maintenance
    item. The filters have to be cleaned or changed every x months. You
    have to remember to do it. If you forget, the computer might overheat.
    The most endangered component is probably the disk drive, and
    the computer will continue to run quite happily under conditions that
    are trashing the disk.


    Some other threads from my search:

    http://forums.pcper.com/showthread.php?s=&postid=2029294

    http://forums.overclockersclub.com/?showtopic=8412&st=10&

    The interesting tidbit on the following site is

    CFM = 3.16 x Watts / Delta_T_degrees_F

    http://www.chassis-plans.com/cooling_and_noise.html

    Using the AMD recommendation of a max case temp rise of 7C, which
    is 12.6F, and assuming 200W for a high end PC, we get 50 CFM.

    This one is a home brew solution, using an air cleaner filter
    replacement as the filter for the air. Positive case pressure
    is created by two identical fans, with one running 200RPM higher
    than the other:

    http://www.silentpcreview.com/Sections+index-req-printpage-artid-144.html

    So, if the air is filtered, then a positive air flow seems to be
    the solution offered by commercial designs. For unfiltered
    situations, a balance between in and out, or a slight negative
    pressure seem to be favored.

    I can tell you that one computer I use, which has only exhaust
    fans, is filthy inside. Yet, I've never had any trouble with
    the floppy or the CD on that computer.

    This is one of those questions, where if you ask twelve
    people, you'll get a dozen different answers :-)

    HTH,
    Paul
  2. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    It's probably as good idea to get one of these...

    http://www.directron.com/110alert.html

    I have one near my HD.

    Prang

    On Mon, 26 Jul 2004 04:20:58 -0400, nospam@needed.com (Paul) wrote:

    >As soon as you use filters on a PC case, then you've got a maintenance
    >item. The filters have to be cleaned or changed every x months. You
    >have to remember to do it. If you forget, the computer might overheat.
    >The most endangered component is probably the disk drive, and
    >the computer will continue to run quite happily under conditions that
    >are trashing the disk.
  3. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    How would that keep out the dust?? It would seem if any fans are blowing in,
    they would bring in dust with the inbound air and any positive air pressure
    inside the case would limit the amount of incoming air for ventillation.
    Don't get me wrong, I would like to see a solution beside airflow limiting
    filters since I have cleaned out dustbunnies of record size and number from
    a few hundred enterprise computers over the years and I would like very much
    to keep the dust out of my new build.

    MkeSp
    ----------------------------
    "Winey" <NOSPAMME@no-one-here.com> wrote in message
    news:0m89g09l8i0g8fcq6e5eqhcq9ir5atusg8@4ax.com...
    > I'm upgrading a case (and the system inside it)? Actually two such
    > systems. I want to have positive air pressure in the case sufficient
    > to keep out dust. If you know this design, it has vents on the sides
    > of the case near the top, plus a row of vents in the back above the
    > adapter cards:
    >
    > Both cases will have an ASUS A7M-w266 D,TBred 2000, no overclocking.
    >
    > Power Supply is an Antec TruePower 550. (assume 0 cfm out at lowest
    > fan speed, 40 cfm at highest fan speed)
    >
    > Cases are an Addtronics 7896A and a 6896A.
    >
    > Assume roughly 140 cfm in. (2 120 mm Panaflow "L" model)
    >
    > So, my question is:
    >
    > How positive do I need to keep the case air pressure, to keep dust
    > out? That is, how much more should the cfm in be compared to the cfrm
    > out?
  4. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    Unless you have filters on the air inlets the dust is gonna get into the
    case anyway.... and if you do have filters then the performance of the fans
    will be much reduced.
    If you have filters and want to ensure positive pressure then the only sure
    fire way is don't have any exhaust fans.

    --
    *****Replace 'NOSPAM' with 'btinternet' in the reply address*****
    "Winey" <NOSPAMME@no-one-here.com> wrote in message
    news:0m89g09l8i0g8fcq6e5eqhcq9ir5atusg8@4ax.com...
    > I'm upgrading a case (and the system inside it)? Actually two such
    > systems. I want to have positive air pressure in the case sufficient
    > to keep out dust. If you know this design, it has vents on the sides
    > of the case near the top, plus a row of vents in the back above the
    > adapter cards:
    >
    > Both cases will have an ASUS A7M-w266 D,TBred 2000, no overclocking.
    >
    > Power Supply is an Antec TruePower 550. (assume 0 cfm out at lowest
    > fan speed, 40 cfm at highest fan speed)
    >
    > Cases are an Addtronics 7896A and a 6896A.
    >
    > Assume roughly 140 cfm in. (2 120 mm Panaflow "L" model)
    >
    > So, my question is:
    >
    > How positive do I need to keep the case air pressure, to keep dust
    > out? That is, how much more should the cfm in be compared to the cfrm
    > out?
  5. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    Amir Facade wrote:
    > I think the exhaust hose on a medium size shop vac would do the trick
    > nicely.


    You included over 100 lines of previous post, what ARE you talking about?

    Ben
    --
    A7N8X FAQ: www.ben.pope.name/a7n8x_faq.html
    Questions by email will likely be ignored, please use the newsgroups.
    I'm not just a number. To many, I'm known as a String...
  6. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    > >I'm upgrading a case (and the system inside it)? Actually two such
    > >systems. I want to have positive air pressure in the case sufficient
    > >to keep out dust.
  7. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    Amir Facade wrote:
    >>> I'm upgrading a case (and the system inside it)? Actually two such
    >>> systems. I want to have positive air pressure in the case sufficient
    >>> to keep out dust.

    Bloody hell. learn how to post.

    The exhaust system from a vac would be warm air and not ideal. Might be a
    bit noisy too.

    Ben
    --
    A7N8X FAQ: www.ben.pope.name/a7n8x_faq.html
    Questions by email will likely be ignored, please use the newsgroups.
    I'm not just a number. To many, I'm known as a String...
  8. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    "NEM" <NoE-Mail@FakeAddress!.corn> wrote

    > By making the room the computer sits in have less dust to begin with.

    Air cleaner with filter!
    Ion generator to stick dust to the walls!


    --
    Ed Light

    Smiley :-/
    MS Smiley :-\

    Send spam to the FTC at
    uce@ftc.gov
    Thanks, robots.
  9. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    notritenoteri wrote:
    > ever thought of vacuming out the guts once in a while?

    Yeah, but the static build up worries me.

    Of course compressed air (or LPG or..) would be more suitable

    Ben
    --
    A7N8X FAQ: www.ben.pope.name/a7n8x_faq.html
    Questions by email will likely be ignored, please use the newsgroups.
    I'm not just a number. To many, I'm known as a String...
  10. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    Bx.Cornwell wrote:
    > you'd think that computer case engineers (designers?) would at least be
    > keeping an eye on things like that...

    BTX design should improve a whole load of things, apparently.

    Ben
    --
    A7N8X FAQ: www.ben.pope.name/a7n8x_faq.html
    Questions by email will likely be ignored, please use the newsgroups.
    I'm not just a number. To many, I'm known as a String...
  11. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    On Mon, 26 Jul 2004 15:05:15 -0500, in <three different newsgroups>, "Michael
    S." <mspurgeon5@comcast.net> wrote:
    >
    > How would that keep out the dust?? It would seem if any fans are blowing
    > in, they would bring in dust with the inbound air
    [snip]

    The presumption is that any/all inward-facing fans would be drawing through
    proper washable/replacable-element filters. Most of your better case designs
    make provision for this (tho' far too many of them -- including such
    "high-end" brands as Lian-Li -- then effectively defeat it by adding way too
    many *exhaust* fans, thus making it difficult/impossible to avoid a negative
    internal case pressure).

    > ... and any positive air pressure inside
    > the case would limit the amount of incoming air for ventillation.
    [snip]

    In theory, perhaps. But as a practical matter, you'll never generate a
    significant pressure differential, let alone one sufficient to have a
    noticeable effect on this. The cases are just too "leaky".

    > Don't get me wrong, I would like to see a solution beside airflow limiting
    > filters since I have cleaned out dustbunnies of record size and number from
    > a few hundred enterprise computers over the years and I would like very
    > much to keep the dust out of my new build.
    >
    [snip]

    Proper filters on the supply fans will never have an excessive negative effect
    on airflow *if* two things are true:

    1. - The fans (and filters) are properly sized for the task in the first place
    (and permitted to run fast enough to do their job, of course).

    2. - The filters are kept clean.

    --

    Jay T. Blocksom
    --------------------------------
    Appropriate Technology, Inc.
    usenet01[at]appropriate-tech.net

    "They that can give up essential liberty to obtain a little temporary
    safety deserve neither liberty nor safety."
    -- Benjamin Franklin, Historical Review of Pennsylvania, 1759.
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  12. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    On Thu, 29 Jul 2004 15:03:08 GMT, in <three different newsgroups>, "Roger
    Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote:
    >
    [snip]

    > Dust was the reason the original IBM design, had the rear fans blowing
    > into the case. The idea was that the intake here was higher, and further
    > from the carpet/user, and the outflow of air at the front would keep the
    > floppy disk from filling with fluff.
    [snip]

    Uhhh... No.

    First, "the original IBM design" (in fact, the first *several* IBM-PC designs)
    used a "desktop" (i.e., horizontal) case; so the fan was *not* (significantly)
    higher than any other part of the system. It wasn't until the "PS/2" line
    came along that IBM offered a "tower"-style PC.

    Second, the unfiltered inward-facing fan was a product of basically two
    factors:

    1. - They weren't really concerned with force-cooling any other part of the
    system beyond the PSU itself; recall that the CPUs didn't even have passive
    heat sinks, let alone active (fan-driven) ones. It simply wasn't an issue.

    2. - $$$. This was _the_cheapest_ way to accomplish what they set out to do.

    --

    Jay T. Blocksom
    --------------------------------
    Appropriate Technology, Inc.
    usenet01[at]appropriate-tech.net

    "They that can give up essential liberty to obtain a little temporary
    safety deserve neither liberty nor safety."
    -- Benjamin Franklin, Historical Review of Pennsylvania, 1759.
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Unsolicited advertising sent to this domain is expressly prohibited under
    47 USC S227 and State Law. Violators are subject to prosecution.
  13. Archived from groups: alt.comp.hardware.overclocking,alt.comp.hardware.overclocking.amd,alt.comp.periphs.mainboard.asus (More info?)

    "Winey"
    > How positive do I need to keep the case air pressure, to keep dust
    > out?
    I'm sorry if this is already covered in this long thread, I didn't have time
    to read it.

    I would think anything positive will work, airflow is deciding factor in
    cooling. I just used packaging tape to cover every vent opening in the case
    and have three fans blowing in and two blowing out. A filter is a great
    idea if you clean it once a month. I just went to Home Depot and rigged
    something up with some AC filter material. Simple, cheap and works great.
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