I have one sitting on a shelf. No air-conditioning. The top plate is warm, far from hot. Will they be happy if I stack another one on top of it? The users guide says 50C. What does that mean if they don't specify the air flow? Is there an assumption that it is floating with lots of empty space around it or something similar? -- These are my opinions. I hate spam.

Hal, in cases where it is physically applicable, the temperature rating is generally that of the flange which is intended to be bolted to a heat sink. Dana On Mon, Jul 19, 2021 at 7:30 AM Hal Murray <halmurray+timenuts@sonic.net> wrote: > > I have one sitting on a shelf. No air-conditioning. The top plate is > warm, > far from hot. > > Will they be happy if I stack another one on top of it? > > The users guide says 50C. What does that mean if they don't specify the > air > flow? Is there an assumption that it is floating with lots of empty space > around it or something similar? > > > -- > These are my opinions. I hate spam. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send > an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there. >

Hi The implicit assumption on pretty much all telecom gear these days is moving air. How much moving air? You would have to get into the spec for the OEM that bought it. It might be listed there, it could easily have been in somebodies notes from a phone conversation ….. As long as the case temperature in your stack does not get much above 50C, the device should be happy. MTBF wise, the hotter it gets, the quicker it fails … sorry about that. Bob > On Jul 19, 2021, at 8:29 AM, Hal Murray <halmurray+timenuts@sonic.net> wrote: > > > I have one sitting on a shelf. No air-conditioning. The top plate is warm, > far from hot. > > Will they be happy if I stack another one on top of it? > > The users guide says 50C. What does that mean if they don't specify the air > flow? Is there an assumption that it is floating with lots of empty space > around it or something similar? > > > -- > These are my opinions. I hate spam. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there.

Since I built an AC supply in my 3801, I replaced the solid top cover with a copper mesh due to the extra heat caused by the linear supply that I built inside it. It has been working fine for the last 18 years. Regards - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 848-245-9115 -----Original Message----- From: Dana Whitlow <k8yumdoober@gmail.com> Sent: Monday, July 19, 2021 9:02 AM To: Discussion of precise time and frequency measurement <time-nuts@lists.febo.com> Subject: [time-nuts] Re: Z3801A Temperature Hal, in cases where it is physically applicable, the temperature rating is generally that of the flange which is intended to be bolted to a heat sink. Dana On Mon, Jul 19, 2021 at 7:30 AM Hal Murray <halmurray+timenuts@sonic.net> wrote: > > I have one sitting on a shelf. No air-conditioning. The top plate is > warm, far from hot. > > Will they be happy if I stack another one on top of it? > > The users guide says 50C. What does that mean if they don't specify > the air flow? Is there an assumption that it is floating with lots of > empty space around it or something similar? > > > -- > These are my opinions. I hate spam. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe > send an email to time-nuts-leave@lists.febo.com To unsubscribe, go to > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com To unsubscribe, go to and follow the instructions there.

Hi, Well, "ambient temperature" as per telecom terminology means the temperature of the surrounding air in the aisle of the rack. The Bellcore/Telcordia GR-63 and ETSI EN 300 019 (series) would stand for the formal definition. This is also in line with the AT&T Reliability manual. It is expected that the ambient temperature of the rack causes a raise of 25 degrees C as you get into the components on the circuits boards, giving the 70 degrees C commercial spec, raising it from the normal 45 degrees C of Belcore/Telcordia GR-63. Other specs is used for non-central office locations, but about the same reasoning of ambient temperature applies. The ambient temperature of the rack then boils down to how the individual equipment was built. Some use fans, while others doesn't. The Z3801A for sure is not built with a fan, but then it is not a direct rack unit device, but an odd-factored sub-rack unit. I kind of doubt that the rack-unit that the Z3801A slides into had a fan to it, but then this goes back to the day and age when some of the rack units was allowed to be so spaceaous that no fan was needed, so that self convection could work. We do not do that very often these days, as rack space is expensive and the power we push into a design is such that forced convection is the way we need to go most of the times, unless someone goes for liquid cooling. There is a fine balance between cooling to keep component ambient temperature down and keep the oven current low and with that the oven controller wear down. I would consider not stacking the Z3801A to densly with other things, so there is a reasonable chance to keep cool. Cheers, Magnus On 2021-07-19 15:19, Bob kb8tq wrote: > Hi > > The implicit assumption on pretty much all telecom gear these days > is moving air. How much moving air? You would have to get into the > spec for the OEM that bought it. It might be listed there, it could easily > have been in somebodies notes from a phone conversation ….. > > As long as the case temperature in your stack does not get much above > 50C, the device should be happy. MTBF wise, the hotter it gets, the > quicker it fails … sorry about that. > > Bob > >> On Jul 19, 2021, at 8:29 AM, Hal Murray <halmurray+timenuts@sonic.net> wrote: >> >> >> I have one sitting on a shelf. No air-conditioning. The top plate is warm, >> far from hot. >> >> Will they be happy if I stack another one on top of it? >> >> The users guide says 50C. What does that mean if they don't specify the air >> flow? Is there an assumption that it is floating with lots of empty space >> around it or something similar? >> >> >> -- >> These are my opinions. I hate spam. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com >> To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-leave@lists.febo.com > To unsubscribe, go to and follow the instructions there.