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Thread: Walk-in: matching compressor with evaporator

  1. #1
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    Walk-in: matching compressor with evaporator

    hi folks, quick question here regarding my walk-in cooler...

    I've been battling my new walk-in cooler for almost a year, having all kinds of problems maintaining temps, compressor coming on and off too much, and the evaporator icing up like crazy (air defrost system).

    I'm in western panama, so getting good tech help is tough. I finally got a hold of a guy with actual training in hvac and engineering and he's saying the root problem is they sold me a compressor that's way too big, not only for the walk-in, but for the evaporator inside said walk-in.

    stats: compressor is approx 22,000 btu's
    evaporator is approx 13,000 btu's
    walk-in is just a 9x9x9 foot cube, insulated except for floor (tile), under roof, ambient temp 65F (high up in the mountains), not opening
    the door often at all, therefore not a big load requirement

    i'm told that you can have a larger capacity evaporator than compressor and it's not such a big deal.

    however, you can't have a smaller evaporator than compressor (which is what i have). i suppose the metaphor would be sticking a high horse power engine in a car without dealing with the transmission. the transmission then blows up one day.

    before i go raise hell at the refrigeration store, i'd like to confirm this diagnosis. any input is much appreciated. thanks!

  2. #2
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    Walk In Configuratiion

    " i'm told that you can have a larger capacity evaporator than compressor and it's not such a big deal. "
    This statement is correct within a relative range.
    You have not given detailed anough information for a sizing match.
    BTU/hr figures are published for equipment at different evaporator and condensing temperatures, and these are critical with respect to the application.
    Typical Evaporator temp range for walkin refrigeration is 20F.
    If your condensing unit is " Ovesized " relative to the evaporator, this is indeed not good at all.
    It can and will cause a myriad of problems that come under the heading of " bad install."
    Said problems cannot be sorted out if the gear is mismtached, and if the oversize is much at all it can destroy the compressor in short order.

    Walk in Refrigeration is one of the easiest HVACR systems to set up, but sadly the real craftsmen that know how to do it well are fading away in the mediocrity of the age we are living in, and for good reason. I used to do nothing but install walk in systems in the Texas Commercial Market. EPA meddling has made things far more complicated than they once were as well, and this is also based on totally fradulent science.

    Star
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  3. #3
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    Quote Originally Posted by Starcat View Post
    " i'm told that you can have a larger capacity evaporator than compressor and it's not such a big deal. "
    This statement is correct within a relative range.
    You have not given detailed anough information for a sizing match.
    BTU/hr figures are published for equipment at different evaporator and condensing temperatures, and these are critical with respect to the application.
    Typical Evaporator temp range for walkin refrigeration is 20F.
    If your condensing unit is " Ovesized " relative to the evaporator, this is indeed not good at all.
    It can and will cause a myriad of problems that come under the heading of " bad install."
    Said problems cannot be sorted out if the gear is mismtached, and if the oversize is much at all it can destroy the compressor in short order.

    Walk in Refrigeration is one of the easiest HVACR systems to set up, but sadly the real craftsmen that know how to do it well are fading away in the mediocrity of the age we are living in, and for good reason. I used to do nothing but install walk in systems in the Texas Commercial Market. EPA meddling has made things far more complicated than they once were as well, and this is also based on totally fradulent science.

    Star
    thanks, warren. great info and pretty much confirming what i'm thinking. if it's hard to get good hvac help in the states, here in panama it's almost impossible, and that's with all the trades. no one reads manuals, they just do what someone taught them 10 or 20 years ago and never change. i usually wind up knowing more than them after watching 3 youtube videos on the subject. i don't blame them, it's really the horrific public education system. panama has all the money they need to have good schools, but the politicos never had the will to do anything substantial. a survey a while back found half the math teachers couldn't do basic algebra. but i digress...

    i'll be paying a visit to the outfit that sold me the equipment. showdown at the not-so-ok corral.

  4. #4
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    Numbers

    Quote Originally Posted by PWB View Post
    thanks, warren. great info and pretty much confirming what i'm thinking. if it's hard to get good hvac help in the states, here in panama it's almost impossible, and that's with all the trades. no one reads manuals, they just do what someone taught them 10 or 20 years ago and never change. i usually wind up knowing more than them after watching 3 youtube videos on the subject. i don't blame them, it's really the horrific public education system. panama has all the money they need to have good schools, but the politicos never had the will to do anything substantial. a survey a while back found half the math teachers couldn't do basic algebra. but i digress...

    i'll be paying a visit to the outfit that sold me the equipment. showdown at the not-so-ok corral.
    If you can get exact numbers off the machinery I may be able to tell you more. I would need to know the refrigerant type, voltage, and phase. All nameplate data of both the evap and condenser.

    Star
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  5. #5
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    thanks, i'll try to get that info on the board tomorrow.

    electricity is single phase. the evaporator is 115V. more info to come...

  6. #6
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    Quote Originally Posted by PWB View Post
    thanks, i'll try to get that info on the board tomorrow.

    electricity is single phase. the evaporator is 115V. more info to come...
    got sidetracked, here is that info, finally.
    Attached Images Attached Images   

  7. #7
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    Condensing Unit M/N

    Quote Originally Posted by PWB View Post
    got sidetracked, here is that info, finally.
    Ok you have given the compressor model number, but whats really needed is the Condensing Unit Model and serial.
    Your evaportor is rated at 12,000 BTU/hr.
    That compressor is rated at 21,837 BTU/hr, but we do not know at what evaporator temp. I had to convert stupid metrics [KW] to American terms.
    Danfoss DOCs do not give such details today of the type we use in the USA. Also its a major trend in all Technical machinery that the documentation is getting worse by the year.
    They are publishing meaningless data, and leaving out the most important things needed for field engineering.
    At a glance I do not like the look of it. Typically the functional capacity of a condensing unit for a matched coil at 20F will come out to slightly LESS than the evaporator rated capacity.
    Without more concrete information, I'd say you do have a mismtach of a hack job, and it sounds like this outfit will connect anything they have on hand without respect for the math.
    The thing is, a combination as thus is a compressor destroyer and can never work correctly.
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  8. #8
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    Boquete, Chiriqui, Rep. of Panama
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    Quote Originally Posted by Starcat View Post
    Ok you have given the compressor model number, but whats really needed is the Condensing Unit Model and serial.
    Your evaportor is rated at 12,000 BTU/hr.
    That compressor is rated at 21,837 BTU/hr, but we do not know at what evaporator temp. I had to convert stupid metrics [KW] to American terms.
    Danfoss DOCs do not give such details today of the type we use in the USA. Also its a major trend in all Technical machinery that the documentation is getting worse by the year.
    They are publishing meaningless data, and leaving out the most important things needed for field engineering.
    At a glance I do not like the look of it. Typically the functional capacity of a condensing unit for a matched coil at 20F will come out to slightly LESS than the evaporator rated capacity.
    Without more concrete information, I'd say you do have a mismtach of a hack job, and it sounds like this outfit will connect anything they have on hand without respect for the math.
    The thing is, a combination as thus is a compressor destroyer and can never work correctly.
    great info, thanks very much. you're confirming what my engineer buddy down here is telling me.

    customer service down here tends to be shaky, but the geniuses that sold me this equipment went above and beyond (in a really, really bad way). they sold me the equipment, recommended the tech, and will take zero responsibility. first came the lady with the super impatient and accusatory tone, which i called her on, politely. then their engineer chimes in and completely disagrees with what everyone else is concluding. i said, well, show me the evidence/literature and i'll believe you. then he said it was his opinion, but it didn't mean others were wrong. i said that's precisely what your opinion means. it started to sound like what "is" is. back and forth dance of the idiots....

    flash forward to me screaming very bad words into my phone in front of sundry folks buying their morning lottery tickets on the street. i may have scarred some old ladies for life.

    cherry on top was the tech who installed the whole cold room told the equipment company that he didn't answer my calls anymore because i owed him money. which i don't. and i would answer the phone of someone who owed me money. maybe i could get my money. welcome to bizarro world, panama. a lovely country where about once a week a wormhole opens up under you and nothing makes sense.

    thanks again for all the help. i'll get this straightened out and have fun making more beer.

  9. #9
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    Choices

    Quote Originally Posted by PWB View Post
    great info, thanks very much. you're confirming what my engineer buddy down here is telling me.

    customer service down here tends to be shaky, but the geniuses that sold me this equipment went above and beyond (in a really, really bad way). they sold me the equipment, recommended the tech, and will take zero responsibility. first came the lady with the super impatient and accusatory tone, which i called her on, politely. then their engineer chimes in and completely disagrees with what everyone else is concluding. i said, well, show me the evidence/literature and i'll believe you. then he said it was his opinion, but it didn't mean others were wrong. i said that's precisely what your opinion means. it started to sound like what "is" is. back and forth dance of the idiots....

    flash forward to me screaming very bad words into my phone in front of sundry folks buying their morning lottery tickets on the street. i may have scarred some old ladies for life.

    cherry on top was the tech who installed the whole cold room told the equipment company that he didn't answer my calls anymore because i owed him money. which i don't. and i would answer the phone of someone who owed me money. maybe i could get my money. welcome to bizarro world, panama. a lovely country where about once a week a wormhole opens up under you and nothing makes sense.

    thanks again for all the help. i'll get this straightened out and have fun making more beer.
    I have considered going to be a Mechanic at large in the third world. I know a guy who did this in his youth in a very different time and his words were "you can live like a king in those realms."
    I do know an Electrical sales guy who ended up in Panama somewhere.

    Star
    Warren Turner
    Industrial Engineering Technician
    HVACR-Electrical Systems Specialist
    Moab Brewery
    " No Cell Phone Zone."

  10. #10
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    Boquete, Chiriqui, Rep. of Panama
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    you got that right. let's put it this way, i've paid mediocre tradesmen twice or three times as much as the local going rate, simply because they showed up within an hour of when they said they would, have some semblance of real training, and most importantly, don't leave the issue at hand more broken than when they arrived. if someone is actually really good, they can easily charge 4 times the going rate to the large and growing expat population. other hot spots are colombia, ecuador, and probably still costa rica, though many are fleeing the super high taxes there.

    gotta say it again, i don't blame these local guys so much. the public education system fails utterly in teaching the number one lesson, how to learn. there's also a cultural macho pride thing where admitting fault or ignorance is worse than death. just how they're raised. they won't read manuals because they literally don't know how to process and use that info. just repeat what someone taught them 5 or 30 years ago. women, on the other hand, are kicking ass and educating the heck out of themselves. i swear if i hear of a female plumber or electrician i'll hire her immediately, playing the odds.

    all this bitching aside, panama has the living happy thing down pat. friendships and family and all the non-economic stuff. us gringos could learn a lot from latinos in that regard. nowhere is perfect, just gotta find the place that fits your person.

    boy did we digress... thanks again, star.

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