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  1. #27
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by rayr View Post
    I am inclined to agree with bob sch_scheel and wannafreeze. The only information missing here is the SIZE of the box and the composition of it. Please supply that information so that we can get a more clear picture of the entire installation.
    box is 15' by 10' with almost 8' ceiling. cement floor is 12" thick with 4" insulation under that. don't know why it was poured so thick. walls are 6" and 1 metal door.

  2. #28
    Join Date
    May 2008
    Location
    Wisconsin
    Posts
    24
    Quote Originally Posted by bob_scheel View Post
    As old as this unit is the insulation in the box walls may have deteriorated. Have you checked for ice in the walls? Is there condensation on the exterior?
    Are seams caulked vapor tight?

    How's the door/ door gasket / floor sweep.

    Being 800 btus short shouldn't raise your box temp by 30 degrees.
    box appears to be o.k. and now I am running a box temp of 12 degrees

  3. #29
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    Quote Originally Posted by hoofbeat View Post
    box is 15' by 10' with almost 8' ceiling. cement floor is 12" thick with 4" insulation under that. don't know why it was poured so thick. walls are 6" and 1 metal door.
    undersize
    -20* evap comp about 7500 btu . you need over 10.000 btu due to old box . low on 2500 btu if you want bring down to -10* need big pump
    Last edited by sarpanch2001; 09-20-2008 at 11:25 AM.

  4. #30
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,264

    I agree with it being undersized...

    You stated that the original unit was rated at 9000 Btuh at -30ºF evap temp. The current compressor (CF09K6E), which comes in an FJAL-B301-CFV condensing unit, will only do 6330 Btuh at -30ºF evap temp.

    I ran a quick load calc on this box. For a -12ºF box temp you need approximately 11,000 Btuh at about a -25ºF evap temp...and that's just for storage, not heavy useage.
    Last edited by icemeister; 09-20-2008 at 03:13 PM. Reason: added minus sign to box temp...oooops

  5. #31
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    5,996
    Just goes to show that you certainly need ALL the information to form a conclusion. The size of the box was really the most important factor and that was an unknown until now. And still the insulation of the walls and ceiling is unknown. Heatcraft program comes up with about 12,500 btu for -30 with a 1,200 lb product load. That is for Urethane walls. That is for medium usage.
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  6. #32
    Join Date
    Nov 2005
    Location
    Haymarket VA
    Posts
    642
    Quote Originally Posted by icemeister View Post
    You stated that the original unit was rated at 9000 Btuh at -30F evap temp. The current compressor (CF09K6E), which comes in an FJAL-B301-CFV condensing unit, will only do 6330 Btuh at -30F evap temp.

    I ran a quick load calc on this box. For a -12F box temp you need approximately 11,000 Btuh at about a -25F evap temp...and that's just for storage, not heavy useage.
    you are right on i was using my rule of thumb just for idea

  7. #33
    Join Date
    Jun 2006
    Location
    Omaha, Nebraska
    Posts
    861
    I'm somewhat of a n00b to refrigeration, but I can barely cool a 15' X 10' bedroom to 72 Deg. with a 9,000 BTU window unit. How are you going to get a box below zero with the same size low-temp unit? Does the insulation make the huge difference?

  8. #34
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    5,996
    Quote Originally Posted by man from trane View Post
    I'm somewhat of a n00b to refrigeration, but I can barely cool a 15' X 10' bedroom to 72 Deg. with a 9,000 BTU window unit. How are you going to get a box below zero with the same size low-temp unit? Does the insulation make the huge difference?
    LOL your ac unit is rated at a 40 deg evap.
    Last edited by rayr; 09-21-2008 at 05:25 PM.
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  9. #35
    Join Date
    Jun 2006
    Location
    Omaha, Nebraska
    Posts
    861
    Quote Originally Posted by rayr View Post
    LOL your ac unit is rated at a 40 deg evap.
    I think I get it- the difference is 9,000 BTUs @ 40 deg evap is a lot less horsepower than 9,000 BTUs @ -20 evap, right? So the compressor is actually much larger in this walk-in freezer even though it's rated for the same BTUs.

    Told you I was a n00b.

  10. #36
    Join Date
    Jul 2007
    Location
    regina saskatchewan
    Posts
    257
    Quote Originally Posted by icemeister View Post
    You stated that the original unit was rated at 9000 Btuh at -30ºF evap temp. The current compressor (CF09K6E) , which comes in an FJAL-B301-CFV condensing unit, will only do 6330 Btuh at -30ºF evap temp.

    I ran a quick load calc on this box. For a -12ºF box temp you need approximately 11,000 Btuh at about a -25ºF evap temp...and that's just for storage, not heavy useage.
    Coincidentally I have worked on a system with the same compressor as above(CF09K6E).This one compressor runs both a cooler and freezer.box dimensions are 6.5x7x7 on each walk-in.Temps are 0f and 40f.I believe it had 12 psi suction.Doesn't shut off very often though from what I remember.One question though.How much does the size of the condensor coil affect btu rating.If any?
    Last edited by cretan; 10-02-2008 at 02:47 PM.
    Artificial Intelligence is no match for Natural Stupidity

  11. #37
    Join Date
    Feb 2004
    Location
    Kansas
    Posts
    18
    Id start by removing the ZP element and replacing it with a standard element. That pressure limiting crap is for the birds.

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