Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: legg Newsgroups: sci.electronics.design Subject: Re: Ambient temperature control Date: Tue, 02 Jul 2024 10:33:50 -0400 Organization: A noiseless patient Spider Lines: 94 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Injection-Date: Tue, 02 Jul 2024 16:31:54 +0200 (CEST) Injection-Info: dont-email.me; posting-host="8df348ca110ecd47d38915e09c47f34e"; logging-data="1772144"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX181JWorypstw51dkD58LLwE" Cancel-Lock: sha1:up0FL+dZbUznnL1fFQRb+Kt5mhw= X-Newsreader: Forte Agent 4.2/32.1118 Bytes: 5552 On Mon, 1 Jul 2024 06:41:26 -0700, Don Y wrote: >On 7/1/2024 4:24 AM, Martin Brown wrote: >> On 01/07/2024 02:14, Don Y 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)? >> >> There can be for some high performance low level OPamps. Deliberately running >> them as cold as is allowed helps take the LF noise floor down and by more than >> you would predict from Johnson noise. ISTR there was a patent for doing this >> back in the 1980's. Prior to that they tended to heat the front end to obtain >> temperature stability and low drift. >> >> https://ppubs.uspto.gov/dirsearch-public/print/downloadPdf/4883957 >> >> Made possible with the advent of decent solid state TECs. > >We don't design products (industrial/consumer) that are "finicky" -- as >it leads to higher TCOs. You don't want to need to control the environment >*or* have "skilled tradesmen" on staff to maintain/assure correct >performance. > >The most common example (that I can think of) where temperature is >controlled FBO the electronics would be datacenters. But, from the >research I've done, there, they simply set a desired temperature for >the cold aisle and largely ignore the resulting hot aisle temperature >(except to ensure it doesn't climb out-of-bounds). I.e., they >don't close the loop on the hot aisle to control the cold aisle's >setpoint (cascaded control). > >And, they don't get the cold aisle "as cold as possible" so they >acknowledge there are diminishing returns in doing so -- likely >cheaper to just pan on a (potentially) shorter upgrade cycle >than to waste electricity trying to eek out a bit more life. > >Interestingly, I can't find anything other than "lore" to >explain why a *particular* cold aisle temperature is chosen. >Amusing to see how much folks DON'T know about the science >they apply! > >When I designed my disk sanitizer, I did a fair bit of research >regarding temperature effects on drives -- because we process a >shitload (thousands) of *used* drives, annually and you don't want to >reuse a drive that has an increased chance of failure (based on >its previous environment, SMART data or observations while exercising >it). The old "10 degree C" saw proved to be totally inappropriate, >*there*. > >OTOH, I suspect it *is* worth noting for power supplies (as I >see most failures being toasted power supplies in otherwise >"healthy" products). I suspect power *cycling* is a culprit, there >as I've seen failed solder joints where it looked like repeated >thermal expansion had led to the failure. > >>> Also, is there any advantage to minimizing the hysteresis between >>> the ACTUAL operating temperature extremes in such a control strategy >>> (given that lower hysteresis usually comes at an increased cost)? >> >> Depends how temperature sensitive the thing is that you are protecting. The >> example I recall they were aiming for medium term stable 6 sig fig measurements >> with the lowest possible noise. > >I've needed to control temperature in applications where it was >key to the *process* being controlled. E.g., monitoring exhaust >air temperature to determine the "state" of the bed and a cascade >loop on the inlet air handler to drive that to a desired state. > >But, there, you have lots of money for the equipment and can buy >good/precise/fast control with things like face-and-bypass as >the primary controlled variable (so the control loop for the >heater/chiller can be cruder and more energy efficient). > >"In the small", refrigeration is the only practical means of >lowering ambient temperatures. And, that adds to operating costs. >If you can tolerate a wider deadband then the cooling cost >can be lower (e.g., cool to X degrees and let it *soak*, there, >before letting it warm to Y degrees instead of foolishly >trying to maintain the environment at some Z>X and As you likely have LESS ability to precisely size the HVAC >to fit such a small load, deadband becomes a key consequence >of that selection process. > >[Gotta wonder why data centers in northern latitudes don't >exploit outside air more agressively during the winter >months!] > What are the HVAC costs in data processing and server facilities? That's just to maintain ambient <40C. RL