ddr@flux.isr.alaska.edu (Donald D Rice) (06/22/91)
After the building air handlers failed yesterday, the temperature in my office got up into the 90's overnight, primarily due to the VR299 monitor, though the attached DS5000+peripherals no doubt helped. The machine kept running with no apparent problems, but I got to wondering about the rated operating temperatures. In the DS5000 Operator's Guide, under System Unit Operating Conditions, the temperature range is given as 10-40 C, 50-104 F. Does this imply that the machines can operate indefinitely at 104 F with no ill effects, or simply that they will not Halt and Catch Fire in this range? Folklore says that operating temperatures above room temperature, ~ 70 F, reduces the MTBF even if it doesn't crash the machine outright, and I've seen the operators shut down the main campus machines if they can't keep the temperature below about 90 F. But from an engineering standpoint, it isn't clear that a 30 F rise translates into a significant MTBF impact. So, I'd like to know if DEC has anything more definitive on the operating temperature ranges of DECstations. Is the entire 50-104 F range really thought to be satisfactory, or is running these guys at the high end of the range seriously frowned upon? It's summer in Fairbanks when it is 90 F during the day and they play baseball at midnight without any artificial lighting, all the stores have sales that start at midnight, and when you go biking at midnight you see people sitting out on their lawns reading the newspaper... Don -- Don Rice Internet: ddr@flux.isr.alaska.edu Geophysical Institute E-mail: fnddr@alaska.bitnet University of Alaska Phone: (907) 474-7569 Fairbanks, AK 99775 Loran: 64.86N 212.16E
jg@crl.dec.com (Jim Gettys) (06/22/91)
I believe the specs are correct as written... Our machines are often used in harsh environments; they get tested in test chambers at elevated temperature extensively. Think about a factory floor sometime. Machine room machines are often more sensitive, and often when your machine room airconditioner allows the temp. to get to 90, it is broken, and this forces the shutdown before the machine room gets too hot. The other thing to be avoided which stresses machines is rapid temperature change; again, if a machine room airconditioner fails, the temperature often rises quickly, and disk drives can become unhappy. Most of our desktop machines have thermostatically controlled fans these days; the fans run faster when the machine gets hotter, to keep the operating temperature of the components relatively constant. (i.e. hot conditions causes you machine to get noisier!). Just keep the airflow to the machine unrestricted, and check that everything you have is similarly rated, but I believe we mean what we say in the specs... - Jim
ajc@thendara.pa.dec.com (AJ Casamento) (06/22/91)
Don, As Jim Gettys has already pointed out, the system boxes on our DS5000/xxx machines have thermostatically controlled fans. This allows them to speed up when the temperature in the box gets higher. It also allows them to run very slowly/quietly when they are not needed. However, I posted your inquiry to the Reliability Engineers just out of curiousity, and Jim was also correct in that we really do mean what the specifications say. To paraphrase my colleagues, and with NO intent to imply any warranty other than that explicitly in the documentation that is provided with the system (ie. this discussion is ONLY that, just a discussion): * The DS5000/xxx reliability numbers are generated at a target of 25 C but are verified at 40 C. * While the system will probably crash at ~50 C (122 F) it is not likely that the componenets will be permanently damaged below ~55 C (131 F). * The other potential for generating such damage is if you block the ventilation of the system (say by placing it on it's side or putting books along it). * For the system to be in danger of catching fire, it would have to be heated to well over 200 C (400 F). The plastics in the system box, keyboard and monitor are flame retardent and are not intended to support combustion once the flame has been removed (ie. if you hold a torch to it you can make it burn, but if you take the torch away, the flames should go out). While I am not a reliability engineer myself, I would be surprised if the MTBF numbers (Mean Time Between Failures) remains constant when the machine is run at 40 C on a continual basis. That is why ruggedized versions of the systems are made, to support the application needs of industrial/military systems. So, if I've bored you enough, I hope this information satisfies your curiousity. Thanx, AJ ********************************************************************** * AJ Casamento "The question is not whether or * * Digital's TRI/ADD Program not the opinions are mine; but * * 100 Hamilton Ave. UCO1-B rather, which of my personalities * * Palo Alto, CA 94301-1616 do they belong to?" * * 415.853.6744 * * ajc@decwrl.dec.com * **********************************************************************
ddr@flux.isr.alaska.edu (Donald D Rice) (06/25/91)
In article <AJC.91Jun22104209@thendara.pa.dec.com> ajc@thendara.pa.dec.com (AJ Casamento) writes: > > Don, > > As Jim Gettys has already pointed out, the system boxes on our > DS5000/xxx machines have thermostatically controlled fans. This > allows them to speed up when the temperature in the box gets higher. > It also allows them to run very slowly/quietly when they are not > needed. However, I posted your inquiry to the Reliability Engineers > just out of curiousity, and Jim was also correct in that we really > do mean what the specifications say. Thanks, both to you and Jim Gettys. I saw Jim's message on Friday, but yours came along after a network hub overheated and quit. Some PC clones also lost their marbles, but the DECstations did fine. One person on the sunward side of the building shut down his DECstation when the room temperature got near 104 F, but the rest of us survived by turning off the monitors to keep the room temperature under 100. The network hub stayed dead all weekend and finally resumed operation this morning (not DEC equipment; I didn't buy it). I guess the moral is that even in Alaska it pays to buy equipment with a decent operating temperature range...especially when you work in a building with a paleolithic air handling system. Thanks again. Don -- Don Rice Internet: ddr@flux.isr.alaska.edu Geophysical Institute E-mail: fnddr@alaska.bitnet University of Alaska Phone: (907) 474-7569 Fairbanks, AK 99775 Loran: 64.86N 212.16E