cooling of external harddisk enclosure

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I've bought an external enclosure for my 160 Gb harddisk. It doesn't
have a fan, but it is built in such a way that air flow through the
enclosure. Is that enough? Should I be worried about overheating? Does
a bigger HDD generate more heat than a smaller one?

Re: cooling of external harddisk enclosure

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what are you using it for.

If you are just using it for back ups then switch it on to back up and off
when complete.

I have 2 ICY boxes containing 200 and 250 Gb drives which have no fans and
have been no problems.

I sometimes leave them on 24 hours by accident with no problems.

Re: cooling of external harddisk enclosure

Juve wrote:
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I've noticed a difference in temperature, between my lower
capacity disk and the higher one. The difference could be
quite significant with a 1TB drive.

External enclosures are available with fans, so there are
some with good cooling. That is not the end of your problems

What I do, is buy an enclosure with a 40mm square fan in it,
then replace the fan as soon as I get the enclosure. I use
a ball bearing fan, to replace the cheap sleeve bearing fan
that comes with the enclosure. I get good quality fans from
a local electronics store. It is important that the
enclosure use a standard fan (one of the square type), so
it can be easily replaced. There are some enclosures with
larger fans integrated into the plastic of the enclosure,
and those cannot be replaced.

I've also drilled holes near the bottom front of the enclosure,
to provide a better air intake. There are a few enclosures, that
have a fan on the back, but no other holes to allow air flow!

Finding an enclosure that does everything right, so you can
use it without any additional work, is rare.

Good luck,


Re: cooling of external harddisk enclosure

On Sat, 27 Dec 2008 23:02:52 -0800 (PST), Juve

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Whether a passively cooled enclosure provides enough heat
dissipation depends on how it is designed (some holes, or
more holes, and where they are, and how you have the
enclosure situated), what your ambient temperatures are, and
how hot the individual parts on the hard drive are.

A larger drive by virtue of having more platters will run
hotter with all else equal.  Sometimes it is instead a
controller chip or motor regulation part that overheats
instead, independant of capacity (though with more platters
the motor may need more current too).  With luck, some of
these overheating scenarios will only logically lock up the
drive and it is fine (or at worst corrupts some data) once
it cools down again, though to many people the data is worth
more than the drive is if they aren't making another backup
of it.

If you have a thermometer you can measure temperature.  Some
rely on SMART info but that is only a spot-temperature
reading which can be a relative guide but will not reveal
how close to a threshold temperature any other parts on the
whole drive are.  Without a thermometer you can leave the
enclosure closed, run the drive for awhile and do a lengthly
copy operation then power off, open it and feel the drive
casing temperature before it has a chance to cool down much.
It's expected to feel warm, but hot to the touch should
prompt you to add a fan or at the very least drill some
additional vent holes in the casing, some in the bottom or
lower portion of the side panels then some in the opposite
area above the drive so airflow is past the drive and
through the longest path in the enclosure as possible.
Consideration of drive temperature should also include
whether the room ambient temperature is the highest it will
be year-round, for example in minimally or
non-air-conditioned rooms there could be at least 10 degrees
difference in summertime.

Generally many drives in passive enclosures do run fairly
warm, warmer than would be ideal for long lifespan -
especially if that enclosure has the power supply internal
to it, but on the other hand an external PSU in an entirely
closed casing can be yet another point of failure from high
heat over time.

The most conservative answer is use an enclosure with a fan
built in.  If you wish to add a fan to your present
enclosure it is not very difficult, simply cut a hole
corresponding to the size of the fan you wish to use.  Even
a tiny 40mm fan is a big improvement though for fan
longevity I prefer a larger diameter and thicker fan, like a
15-20mm thick, 60mm fan running at lowest RPM it
possibly/reliably can.  A standard household door hole-saw
will make a nice hole for a 60mm fan.  

If there are children or cats around, put a fan grill on it,
or even better a wire mesh or foam filter panel to keep dust
out, though with a filter the following resistor values
might need reduced by about 25 percent to retain good
airflow, although even without considering the reduction in
airflow there will still be a large, probably good enough
improvement in airflow running the fan at minimal RPM with
the following values with a fan filter installed.

Towards that end, I often solder a resistor in series with
the fan power lead, generally a good candidate fan will have
an original rating of between 0.8A and 0.12A current, then
after adding a 1W to 2W, 68 Ohm (for 0.12A) to 120 Ohm (for
0.08A, or since I have a few 0.1A fans and 100 Ohm
resistors, I find that a good inbetween value).  

The above combos of fan plus serial resistor will achieve
very low RPM, often nearly inaudible.  The next step is
determining how to power it.  If it's a 2.5" enclosure it
will have 5V power so you don't need the series resistor,
only to pick a fan that reliably spins at 5V.  With a 3.5"
or 5.25" enclosure it will have a 12V power supply at least,
so the series resistor will manage RPM.  Either way, power
the fan with the existing power for the drive, the fan will
use only a minor amount of power leaving enough for the
drive in any resonably designed product.

If the portion of the case you install the fan onto is the
same part that the power jack is mounted into you can direct
wire the fan to the circuit board where the power input is,
just solder the fan leads onto the PCB.  If the fan instead
mounts to a part of the enclosure shell that removes from
the portion holding the PCB with input power jack, you will
probably want to solder a lead with a connector so the fan
can be unplugged when the enclosure is opened, else a very
long fan lead to allow enough slack to completely open it.  

Re: cooling of external harddisk enclosure

Juve wrote:
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The only way to find out for sure is by measuring the temperature of
the HDD under worst-case conditions (hot room, lots of head seeking)
and by comparing that against the maximum allowed temperature
(probably 55-60C) and the temperature of a similar HD (same diameter
platters, same RPMs) that's in a well-ventilated enclosure or
computer.  Or compare the enclosure to the enclosure used for an HDD
(again, same diameter platters, same RPMs) that's warranted for 5
years by the manufacturer.  Look for vent holes arranged not only so
the air will flow both in and out but also flow all over the HDD
(i.e., in from the front bottom, out the top rear).

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Considering the poor quality of computer accessories, yes, but don't
obsess over it the way some people obsess over CPU temperature or
performance benchmarks.

Here's an example of a bad enclosure, called a Neo:

It has a cooling fan but so few vent holes in front that it's noisier
when the cover is installed than when it's left off, and I'm including
the noise of the HDD.  The HDD sits almost flush with the bottom, so
the drive electronics get almost no air flow (if your enclosure is
similar in this respect, see if you can place some nylon washers
between the drive and enclosure bottom; longer screws may be needed),
and one buyer's HDD burned out a chip, which left a scorch mark in the
enclosure.  The seller, Dealsonic, not only gave him a complete refund
but also replaced his internal HDD.  But worse than the heat is the
electrical safety:  the power supply is internal and is not UL
approved (contrary to what the Dealsonic website originally said), and
normally sits right below the IDE-USB interface card (swung to the
left for visibility), separated only by a thin layer of tough
plastic.   Apparently this power supply has no protection against
overvoltage or overcurrent (except a fuse).

In comparison, look at this much better made Bytecc/Welland enclosure:

It too has an internal power supply, but notice that it's housed in a
metal cage  and is UL approved.  Also the HDD sits about 0.1" - 0.25"
above the bottom, and you can see tiny vent holes around the
indentations for the screws that attach to the HDD.

BTW, external power supplies for enclosures are almost always UL
approved for safety, so I would strongly prefer them over internal

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The drive capacity has nothing to do with it, except when higher
capacity means more platters.  But more important are the diameter of
the platters and the rotational speed.  Drives with 2.5" platters run
stone cold unless placed inside a laptop or unventilated enclosure.
Among drives with 3.5" platters, the 7200 RPM models run pretty hot,
but the 5400 RPM ones get only lukewarm.  The difference in the amount
of power between the latter is only about 3-4 watts, indicating that
it takes just a little extra power to raise the temperature
considerably.  A power supply inside an enclosure will add roughly the
same amount of power -- another reason to prefer external power

Some enclosures are claimed to provide adequate cooling solely through
conduction.  That may be true for 2.5" HDDs, but I have doubts about
this for 3.5" HDDs (but I'm no expert).  And some enclosure makers or
dealers may lie about the conduction cooling.  For example, Buffalo
says that the USB 160GB HDD I have is cooled by conduction, even
though its enclosure is made of thin steel (steel conducts heat
roughly 10x worse than aluminum does) and the internal HDD makes
contact with the enclosure at just three small spots.   I'm not even
sure that my Western Digital 3.5" Elements USB drive is cooled
adequately, despite the enclosure being made of fairly thick
aluminum.  Considering that data recovery costs a lot, lot more than
any enclosure, I often drill extra vent holes in my enclosures (remove
the internal drive first, and be sure to remove all the metal chips
and powder from the drilling and any burrs that may short against the
electronics).'s really long, really thorough thread about external
drive enclosures:

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