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  1. #27
    Join Date
    Jun 2004
    Posts
    847
    Yes
    But I'm not sure if they have a 1 ton condensing unit

  2. #28
    Join Date
    Jun 2004
    Posts
    847
    Quote Originally Posted by KB Cool View Post
    I thinking you got a larger evap than the little condensor can handle. Could be wrong!!! WHy did you install a 1/3 HP? What's the BTU rating of the evap?
    I'm not sure what evap that is but
    I'm guessing 300 on model is around 3000 btu
    But I'm not sure
    Maybe he can google it.

  3. #29
    Join Date
    Feb 2006
    Location
    Phoenix,AZ
    Posts
    2,760
    Quote Originally Posted by shaka View Post
    I'm not sure what evap that is but
    I'm guessing 300 on model is around 3000 btu
    But I'm not sure
    Maybe he can google it.
    Maybe he's okay? But, it just won't pull down?

  4. #30
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,384
    I have tried to google it. Found nothing so far.

    I installed it because he said here put this in. He and I both know I don't know refrigeration.

    He built the box and I ran the wire, installed the condenser, evap, piping, etc....

    I got it up and running but it wont get down to 40* where he wants it.

  5. #31
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,384
    I guess you can say its more of an experiment for me. I can say it works. So I did my job. LOL

  6. #32
    Join Date
    Feb 2006
    Location
    Phoenix,AZ
    Posts
    2,760
    Quote Originally Posted by gravity View Post
    I guess you can say its more of an experiment for me. I can say it works. So I did my job. LOL
    Well, i'm sure the guy can make the box smaller!! Maybe change it into a 4x4!!!

  7. #33
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,080
    The system matches up OK, however it simply doesn't have enough capacity to do the job.

    The Bohn C-30 evaporator is rated at 3000 Btuh at a 10F TD, where the TD is the box temperature minus the evaporator temperature. A 10F TD is a good number to use for a general purpose walk-in, so for a 40F box you would select a condensing unit which has a capacity of approximately 3000 Btuh at a 30F evaporator temperature.

    The Tecumseh AEA4440, which is a 1/3 HP unit, has a capacity of 3020 Btuh at 30F evap, so it is a good match for the C-30 evaporator.

    The expansion valve should be selected to the actual system capacity in tons and not the nominal horsepower. For 3020 Btu, that would be 3020/12000 or about 1/4 ton, so a nominal 1/4 ton TXV should work.

    As for the box load, there are some good calculator available or you could use a quick-select chart. Here's a screenshot of Heatcraft's quick selection guide for a 35F walk-in, which will give you an idea of what this box really needs.

    Name:  screenshot-hearcraft-quickselect.jpg
Views: 473
Size:  106.8 KB

    As you can see, an 8 x 8 cooler should have a system with at least 7000 Btuh capacity for general duty. That would bump you up to a 3/4 HP unit and matching evaporator.

    From the numbers posted, I can see you were measuring superheat at the compressor. For a refrigeration system you should always first set your superheat when the box is near design temp at the outlet of the evaporator close to the TXV bulb location where 6-8F SH is good, but no more than 10F. Then check it at the compressor where it should be no less than 20F.

    Subcooling isn't of much use with a system that has a receiver because adding or removing refrigerant doesn't affect SC significantly, it just changes the level in the receiver.

  8. #34
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,579
    my 8x8 w/i has a 12k window shaker that I made some mods to the stat and added a evap air defrost. Works well, pull down is within an hour after start up.

    Unless you are going to run this box all the time I do not think you have the pull down your buddy will be looking for, then add a hot deer or 2 and a couple guys working makes it worse.

    I gave up the refrigeration world a long time ago, just speaking of my own personal box.

  9. #35
    Join Date
    Jun 2004
    Posts
    847
    Quote Originally Posted by icemeister View Post
    The system matches up OK, however it simply doesn't have enough capacity to do the job.

    The Bohn C-30 evaporator is rated at 3000 Btuh at a 10F TD, where the TD is the box temperature minus the evaporator temperature. A 10F TD is a good number to use for a general purpose walk-in, so for a 40F box you would select a condensing unit which has a capacity of approximately 3000 Btuh at a 30F evaporator temperature.

    The Tecumseh AEA4440, which is a 1/3 HP unit, has a capacity of 3020 Btuh at 30F evap, so it is a good match for the C-30 evaporator.

    The expansion valve should be selected to the actual system capacity in tons and not the nominal horsepower. For 3020 Btu, that would be 3020/12000 or about 1/4 ton, so a nominal 1/4 ton TXV should work.

    As for the box load, there are some good calculator available or you could use a quick-select chart. Here's a screenshot of Heatcraft's quick selection guide for a 35F walk-in, which will give you an idea of what this box really needs.

    Name:  screenshot-hearcraft-quickselect.jpg
Views: 473
Size:  106.8 KB

    As you can see, an 8 x 8 cooler should have a system with at least 7000 Btuh capacity for general duty. That would bump you up to a 3/4 HP unit and matching evaporator.

    From the numbers posted, I can see you were measuring superheat at the compressor. For a refrigeration system you should always first set your superheat when the box is near design temp at the outlet of the evaporator close to the TXV bulb location where 6-8F SH is good, but no more than 10F. Then check it at the compressor where it should be no less than 20F.

    Subcooling isn't of much use with a system that has a receiver because adding or removing refrigerant doesn't affect SC significantly, it just changes the level in the receiver.

    ICE
    Your my hero��

  10. #36
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,384
    sweet...thanks for the info

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