Ambient interior case temperature?

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My case came with a temperature probe connected to a front panel temperature
guage and I just have it hanging in mid-air, away from the hard drives,
video cards, etc.  My question is: what is an acceptable (safe) ambient
temperature for the inside of a computer case?


Re: Ambient interior case temperature?

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There is no nice tidy number.

A system with a better heatsink/fan for the cpu can see
the cpu temperature fine with a higher case internal
temp than one with a poor heatsink/fan for the cpu.

Re: Ambient interior case temperature?

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You can look at case temp from a couple perspectives.

Your disk drive needs to be kept cool. If the humidity of the
air is 60%, the allowed temp for the disk drive is about 36C.
If the air is a lot drier, the temp for the disk drive can be
a bit higher. So that would be one reason to be checking
the air temperature, especially around the disk drive.

The second perspective, is the heatsink on the CPU, cannot
cool the processor below the temperature of the surrounding
air. If the computer case temp is 40C, then the processor
can never go below 40C, and in fact the processor_power *
thermal_resistance, sets the delta between the case air
temp and the CPU temperature. The cooler you make the case
air, the lower the CPU temperature will be. On an Intel
processor, you are trying to avoid the temperature where
the processor uses throttling, and slows your calculations
down (65C-70C or so).

A well cooled case might be 7C delta above ambient. If
the room air is 25C, then the case would be well cooled
at 32C. That is a pretty aggressive target to meet,
especially for a high end system. For a low end system,
(non-gaming video card), it should be much easier to
achieve a number like that.

Top of PDF page 27 says 7C is well cooled:

You can get the temp-humidity curve for a disk drive, by
downloading the OEM manual for the drive from the disk
drive manufacturer's web site. The following numbers
were from OEM doc version 3.2 for an Ultrastar_73LZX -
the link I have to this doc is no longer valid. Possibly
some Seagate docs may contain a graph like this. (The
comments in the right hand column are mine, data is from
the document.)

Relative    Allowed
Humidity    Temp
<14%        55C     (very dry winter conditions - good for drives)
 60%        36C     (carpeting starts to mildew - no AC in summer)
 90%        31C     (unbearable for humans, and for your drive)

Some people get more worked up iabout this stuff than others :-)
For most users, they have to strike a compromise between noise
level and cooling effect. If you have air conditioning in the
room, your computer case cooling requirements are not quite as
demanding, since your room humidity will be around 40%.


Re: Ambient interior case temperature?

On Mon, 26 Jun 2006 22:12:37 -0700, "Bud Dickman"

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It is often considered adequate to strive for <= 10C over
the room ambient temp, but your room ambient temp is another
variable to consider.

If your sensor is nearer the bottom front than the top rear,
it will not be an accurate indication of overall chassis
temp, rather than the result of the front (cooler) intake
air flowing over it before reaching the hotter components in
the case.  Placing it nearer the top middle edge of the
motherboard might be best, or near the corner where the case
meets the motherboard meets the video card, nestled in that
corner as much as possible instead of sticking up near the
exhaust fan.  

That is, unless you wanted to use this probe to monitor
something besides the case ambient temp, which might be a
reasonable thing to do since ultimately the case temp is
only significant to the extent of how it effects the cooling
of, temp of the other parts.  Since some other parts already
have temp senors and readings you can monitor, placing this
probe on a part you can't monitor yet could be useful.
Video card or hard drive are two possibilities, or tacked
onto a mosfet (or it's heatsink if so equipped) in the VRM
(CPU power supply subcircuit) for overclockers who raise
their vCore voltage a lot.

If you just want a generic answer, ideally the chassis
ambient would be under 45C on a low noise system and under
40C on a noisier system.  The better you heatsink the hot
parts inside, the less important it is to have lower ambient
temps, but any suspect parts' temps should be checked after
the case had been left closed for at least 1 hour while the
system runs at full load.... and factoring for the highest
room ambient temp that is every expected or possible.

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