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  1. #14
    Join Date
    Sep 2002
    Location
    Virginia
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    2,747
    Quote Originally Posted by koolkahuna View Post
    When I ran the HVAC/R department of our hospital, one of the freezers in the pharmacy was an ultralow temp cascade system. This freezer is set at -85 celsius/-120 fahrenheit.
    holy friggin ... can you imagine having to repair wiring problems on the evap in that kind of temp ?? Shiver me timbers ...

  2. #15
    Join Date
    Feb 2004
    Location
    British Columbia, Canada
    Posts
    516
    Quote Originally Posted by Snapperhead View Post
    holy friggin ... can you imagine having to repair wiring problems on the evap in that kind of temp ?? Shiver me timbers ...
    Yeah, I always wanted to put one of my coworkers lunches in there and then put it back just before lunch. Problem is that if you dropped it, it would shatter!

  3. #16
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Work on a system like that. Plasma center. Enter 1st box 0 degrees then into the two -40 degree storage boxes. Good setup.

  4. #17
    Join Date
    Aug 2002
    Location
    Southold.calm
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    4,846
    But will you ever achieve 0% RH incoming air?

    Isn’t that like reaching absolute 0?

  5. #18
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,938
    Quote Originally Posted by pecmsg View Post
    But will you ever achieve 0% RH incoming air?

    Isnt that like reaching absolute 0?
    You don't need 0% RH. All you need to do is to get the dewpoint below evap temperature.

    A good HVAC system and a couple layers of refrigeration surrounding it and I think that it is acheivable.

  6. #19
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,938
    Thinking further about it....

    I don't have a problem with the humidity being reduced to a level that negates the need for defrost.

    What I do think that you might have a problem with could be oil return.

  7. #20
    Join Date
    Apr 2003
    Location
    Maple Grove, MN
    Posts
    1,133
    What if for whatever reason, it does need to be defrosted? Then what? Are you going to go in to a 100 below freezer (or however cold it is) with a hair drier or something? Or at that temperature, would the chance of it freezing up be slim enough that you really don't have to worry about it? After thinking about it, maybe whatever frost or ice that is in there would just sublimate away into nothing.

    Relating to what Snapperhead said, though, what WOULD you do if something needed to be repaired in there? Do they have astronaut suits for you to wear or something? I'm guessing my Carhartt bibs and stocking cap wouldn't cut it in there.

  8. #21
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,296
    That's all fine and dandy but the ice cream would definetly be to hard to scoop.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    It was working when I left...
    Liberalism-Ideas so good they mandate them

  9. #22
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Don't know about -100 but I can say that -40 is painful within minuts to any exposed skin.

  10. #23
    Join Date
    Dec 2004
    Location
    WI
    Posts
    312
    I think this is being miss understood.

    I used to work on a great deal of Cascade -70F freezers. They are nearly always reach ins or chest type. I have never seen a -70F walk in. It just is not a good idea to work on. I think it would be extremely dangerous too.

    It sounds like his freezer with in a cooler etc is running normal freezer temps just does not want a temp change as you open the doors to walk in.

    I worked in one place that i shall not name that did animal testing. If you went in one building you could not go into another on the same day..i asked why? they said if you contract a virus they didn't want to transfer it to the other blocks.
    I asked them then why could i go in one the next day? They said you would know for sure you had one by the next day or you would be dead by then! Nice. I hope he was joking.
    The postings on this site are my own and don't necessarily represent The Manitowoc Company's positions, strategies, or opinions.

  11. #24
    Join Date
    Feb 2004
    Location
    British Columbia, Canada
    Posts
    516
    Quote Originally Posted by jonbailey19808 View Post
    I think this is being miss understood.

    I used to work on a great deal of Cascade -70F freezers. They are nearly always reach ins or chest type. I have never seen a -70F walk in. It just is not a good idea to work on. I think it would be extremely dangerous too.

    It sounds like his freezer with in a cooler etc is running normal freezer temps just does not want a temp change as you open the doors to walk in.

    I worked in one place that i shall not name that did animal testing. If you went in one building you could not go into another on the same day..i asked why? they said if you contract a virus they didn't want to transfer it to the other blocks.
    I asked them then why could i go in one the next day? They said you would know for sure you had one by the next day or you would be dead by then! Nice. I hope he was joking.
    This particular cascade freezer in the pharmacy was definitely a reach in. NASA makes use of walk ins for their equipment testing, but I'm not sure that they even need that cold of a temp.

    As per the virus situation, he had to have been joking or OH&S should be involved! You never know with some of those places. We used to get service calls at the agricultural/bovine studies department at a university where the cows had plastic doors installed on the sides of their stomachs by "veterinary surgeons". There were departments for other research there with SERIOUS security measures. Always made me wonder whether they were trying to keep people out or keep something in...

  12. #25
    Join Date
    Dec 2011
    Location
    Fort Worth, TX
    Posts
    80
    Quote Originally Posted by koolkahuna View Post
    This particular cascade freezer in the pharmacy was definitely a reach in. NASA makes use of walk ins for their equipment testing, but I'm not sure that they even need that cold of a temp.

    As per the virus situation, he had to have been joking or OH&S should be involved! You never know with some of those places. We used to get service calls at the agricultural/bovine studies department at a university where the cows had plastic doors installed on the sides of their stomachs by "veterinary surgeons". There were departments for other research there with SERIOUS security measures. Always made me wonder whether they were trying to keep people out or keep something in...
    We have quite a few different types of freezers at a cutting edge hospital I work at. Out lab has the -80C freezers, the CVOR unit keeps some of their stuff at -313F. The MRI low stage (recycled liquid helium) keeps the superconductors of the MRI at absolute zero (I love the whole superconductor theory). Our MEG also uses liquid helium but it does not recycle it, only vents it (manufacturer says it will void the warranty to put a helium recycle unit on it, weird I know). I am the resident HVACR expert at our facility (that just means I have a lot to learn about a lot of things) so I get to work on a lot of stuff.

  13. #26
    Join Date
    Apr 2010
    Location
    San Diego, CA
    Posts
    171
    About 10 years ago I worked on a system here in San Diego that had been running at -40 for years with no defrosts. There's a small ante-room that's kept at 20C that you go into first, on the wall in that room is the control panel for the whole setup. Through the next door you enter into a 4C room that has glass doors on either side. Behind those glass doors it's -40 +/-0.5C at all times. No defrosts. Ever.

    There's a small rack on the roof that handles the cooling for the whole system. Two recips and two screws, fully redundant (one screw, one recip per system) running R507. Next to the rack is a Munters air drier that handles supply air going into the room. Outside air is first dehumidified by a cooling coil fed from the rack, then it goes through a big desiccant wheel and down to the room. Dew point (frost point?) of this dry air last I saw was -86C (indicator on the wall. No idea how accurate this was). Originally there was no air drier and they piped nitrogen into the room to keep it dry, so there's also a bunch of O2 sensors in there, but they were unreliable, so the air drier was installed...

    One of the coolest systems I ever worked on. Back when I was dangerous. (nowhere near enough experience to be playing with such systems...)
    Last edited by cmclifton; 02-28-2013 at 01:16 AM.

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