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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: Ambient temperature control
Date: Tue, 02 Jul 2024 10:30:36 -0400
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On Mon, 1 Jul 2024 13:44:39 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:

>On 7/1/2024 7:34 AM, legg wrote:
>> On Sun, 30 Jun 2024 18:14:32 -0700, Don Y
>> <blockedofcourse@foo.invalid> wrote:
>> 
>>> Assuming you can keep a device in its "normal operating (temperature)
>>> range", how advantageous is it (think MTBF) to drive that ambient
>>> down?  And, is there a sweet spot (as there is a cost to lowering the
>>> temperature)?
>>
>> If all you're thinking of is MTBF, adding the complexity of an active
>> cooling element is a big step in the wrong direction for the system.
>
>Shifting the reliability burden into a (relatively) low-tech, ubiquitous
>subsystem allows failures to be maintained by "non-technical" people.
>It also allows for easier redundancy -- you can add another AHU "in parallel"
>with an existing unit a lot easier than redesigning the electronic
>system to be more reliable over a larger operating range of temperatures.
>
>> Reducing the thermal impedance of the source, to ambient is the
>> usual way to go, when addressing a specific aging factor.
>
>If ambient approaches the limits of the design, then what?
>
>You design something to be able to operate at 50C (on paper).
>It gets deployed *at* 50C.  What sort of failure rate do you expect
>at that elevated temperature vs. operating that same piece of kit
>at 30C by introducing active cooling?  (the assumption being that said
>cooling can be maintained/repaired by a local run-of-the-mill agency)
>
>The question tries to address that issue -- and, the consequences of
>how "well" you strive to maintain a "better" operating environment.
>
>E.g., cooling the environment to 10C and then letting it creep back
>up to 50C before repeating the cycle would be different than keeping
>the device "at" 30C.
>
>Why set a cold aisle temperature of 20C and not 30C?  40C?  Why not
>operate the devices at their specified ambient limits?
>
>     Continuous Operation: 10C to 35C, 10% to 80% relative humidity (RH).
>     10% of annual operating hours: 5C to 40C, 5% to 85%RH. 1% of annual
>     operating hours: -5C to 45C, 5% to 90%RH.
>
>I.e., the cited device CAN operate at 45C.  But, at what cost
>(reliability)?
>
>> https://ve3ute.ca/2000a.html
>> 
>> If you're thinking of performance, It's cheaper and more reliable
>> to concentrate on reducing the temperature of the point source, not
>> the rest of the planet.
>> 
>> RL
>
What's the mtbf of a fan? a compressor? a pump? 
.. . . . or a clamp and a block of aluminum?

Ambient and component temperatures are freely obtained and carefully 
controlled elements in mtbf documentation recording methods.

The former requires $$ equipment.

RL