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Are if there any electrical reasons not to operate or store my Dell OptiPlex computers below the altitude of -50 feet, as written in the specifications?

Screenshot of the original Dell OptiPlex specifications I saw:

Part of the original specification with altitude limits

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    \$\begingroup\$ I don't know either but atmospheric pressure at sea-level and 15°C is 101.325 kPa. At -15 m the pressure increases to 101.505 kPa which is 0.18% higher. This is less than the standard deviation of atmospheric pressure which is about 0.2 kPa in London. The Dead Sea is 430 m below sea level but I imagine that heat will be the problem there rather than pressure which would be 106.598 kPa (at 15°C), +5%. \$\endgroup\$
    – Transistor
    Sep 20 at 11:05
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    \$\begingroup\$ @Transistor normal pressure variations are a good bit more than that ... we'll see about 1030 mB or 103kPa tomorrow (admittedly about 300 miles N of London) \$\endgroup\$ Sep 20 at 20:42
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    \$\begingroup\$ @user_1818839, yes but that's covered in the standard deviation. ±1σ will cover 68% of the time and ±3σ will cover 99% of the time. See the first graph on en.wikipedia.org/wiki/Standard_deviation. \$\endgroup\$
    – Transistor
    Sep 20 at 20:48
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    \$\begingroup\$ Consumer GPS works in airliners over 10000'. GPS is restricted when it goes over 1,000 knots and over 18,000 m, which is really missile-only territory. \$\endgroup\$
    – tomnexus
    Sep 21 at 1:22
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    \$\begingroup\$ @tomnexus a few devices (used to) treat the restriction as or rather than and which may explain the confusion. \$\endgroup\$
    – Chris H
    Sep 21 at 7:45
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From DTB Environmental Chamber Testing

Altitude Testing. Our testing facilities simulate altitudes from below sea level (-2,000 ft), to a high altitude of 100,000 ft.

From Dell™ Inspiron™ 6400/E1505 Owner’s Manual

enter image description here

From Dell PowerVault MD3260/3260i/3660i/3660f/3060e Storage Arrays - Getting Started Guide

enter image description here

The Google search of site:downloads.dell.com/manuals altitude 15.2 gives 1,340 hits. Pure Opinion - Would you believe -50ft to 10,000ft is the limits of their testing facility!

As demonstrated by the DTB Environmental Chamber Testing link, testing facilities can simulate any environment with vacuum pumps. There is nothing unique with -50ft (-15.2m) from a location in the world perspective!

Death Valley is 86 meters below sea level. Odds are Dell products will work there.

If they list -50ft to 10,000ft, then that must be the limits of their testing facility.

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    \$\begingroup\$ It's probably a matter of not making business sense to test deeper, the number of people using their products in such an environment is too low to make it economic. \$\endgroup\$ Sep 21 at 2:27
  • \$\begingroup\$ @LorenPechtel And most of those will probably have enough common sense anyway to know that the -15.2 m is not a hard limit by any means. \$\endgroup\$ Sep 22 at 8:13
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Hard disks are exquisite aerodynamic devices that depend on air pressure for normal operation. The head flies on an air cushion at about 5 nanometres! Here's a picture from a patent:
enter image description here

They have a well known upper altitude limit (Seagate says 10000') but it makes sense they would also have a low limit. I doubt that a few hundred metres would matter, but I would expect them not to work properly at 2 atm.
When not operating, hard disks are very rugged.

Fans in computers, especially servers with powerful fans, might stall if the air density is too high.

Thermal and insulation properties of air improve with higher pressure, so that shouldn't be a problem.

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    \$\begingroup\$ Seagate “Extreme Environment” HDDs are rated to -1000 feet to +18,100 feet. That’s only about +4% higher pressure than sea level vs about -50% at the high (altitude) end. \$\endgroup\$ Sep 20 at 18:57
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    \$\begingroup\$ Yes this is precisely what Dell writes about the upper limit. "The root cause of the issue is that the read/write head of a hard disk drive floats on a thin cushion of air. The air pressure inside the drive is maintained by the hole which communicates with the air pressure outside. At high altitude, the air is too thin to support the head and it might scratch and destroy the disk surface." Regrettably no info on the lower limit. \$\endgroup\$
    – P2000
    Sep 20 at 23:23
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    \$\begingroup\$ @P2000 Given that lower density reduces the air cushion effect, higher density should logically increase it, which in turn could push the heads out of reliable operating range. \$\endgroup\$ Sep 21 at 1:01
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    \$\begingroup\$ @AustinHemmelgarn that would only matter when it was running, presumably. Perhaps they just didn't bother to test their computers under high air pressure. That's more likely. \$\endgroup\$
    – user253751
    Sep 21 at 9:46
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What if it was just testing logistic reasons? In other words, they do not test at lower than minus 50 feet so they do not guarantee the operation of the device.

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    \$\begingroup\$ yup, its tested to, it doesn't mean it won't work outside. Higher altitude comes with increased concerns with SEE type issues and also creepage so setting a HIGH is valid. If they set 0 -> 10,000ft they would get questions from places that are just below sea level (mines, dykes etc..) so it just cuts down on the number of queries. \$\endgroup\$
    – JonRB
    Sep 20 at 11:01
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Yes sir, there is a reason.

You know us engineers -don't you?

Everything is a formula - as is the air pressure at certain elevations. With the change in air pressure comes change in thermal conductivity/radiation/convection rating.

So to not roast your device, the validated operational spectrum is noted in the datasheet.

The keyword is 'validated' and not 'reason'.

Fun question: If altitude is measured in height above sealevel, that would put -50ft below the water surface - which in itself is dangerous for electronics, isn't it?

On the other hand: In the Netherlands, for example, there are areas with below 0 altitudes which are perfectly dry. So maybe your device is rated for use in the Netherlands.

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    \$\begingroup\$ Thermal conductivity / specific heat capacity of air (by volume) should increase with pressure and decreasing altitude. \$\endgroup\$
    – Transistor
    Sep 20 at 10:09
  • \$\begingroup\$ Cite: [The keyword is 'validated' and not 'reason'] @Transistor \$\endgroup\$ Sep 20 at 10:10
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    \$\begingroup\$ NXP is based in the netherlands, mayber this limit comes form some parts thjey made. \$\endgroup\$
    – Jasen
    Sep 20 at 11:37
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    \$\begingroup\$ Validated for Netherlands with min -6.75m, yet can't use it on the Dead Sea though, -430m below sea level. \$\endgroup\$
    – Jeroen3
    Sep 20 at 12:19
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    \$\begingroup\$ There's plenty of places below a water surface that aren't themselves wet. Undersea mining is a thing, as are submarine craft. And that's ignoring the part of the Earth's surface that's lower than sea-level datum. \$\endgroup\$ Sep 21 at 10:15

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