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  1. #1
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    Question Clarification on SUBCOOLING IN DIAGNOSTICS

    @ http://www.achrnews.com/articles/891...-of-the-puzzle

    I am unclear on this portion where the writes states (bold part)

    SUBCOOLING IN DIAGNOSTICS
    So far I’ve talked about subcooling as a charging tool, but it is also an invaluable tool for diagnosing troublesome systems. In fact, if you diagnose a refrigerant system without using subcooling, you have only been guessing.
    Imagine you have two systems with orifice metering devices that have refrigerant system problems. One has a liquid restriction with a normal charge; the other one is undercharged. They both have abnormally low high- and low-side pressures and abnormally high superheat. The only difference between the two systems will be their subcooling. The restricted machine will have abnormally high subcooling and the undercharged machine will have abnormally low subcooling.

    (By the way, many techs seem to think that, contrary to the previous example, a system with a liquid restriction exhibits low suction and high head pressures. This is not the case — although a liquid-restricted system will have excessively high head pressure after several techs misdiagnose it as undercharged and add refrigerant to get the suction pressure up.)
    I mean if machine's metering device is constricted/clogged ..sure compressor discharge gonna rise?

  2. #2
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    Unroll the condenser stacks up and is cooled down. The comp. Can only pump what it gets.

    Sent from my SM-S320VL using Tapatalk

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  4. #3
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    Quote Originally Posted by ioncube View Post
    @ http://www.achrnews.com/articles/891...-of-the-puzzle





    I mean if machine's metering device is constricted/clogged ..sure compressor discharge gonna rise?
    NOPE seen it a bunch of times, if not overcharged discharge pressure would often go down.
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  6. #4
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    One way to look at high head is it represents work being done. If the refrigerant is restricted the system won't do the work it normally would.
    If the refrigerant isn't moving, like Core-d wrote, it will stack (accumulate, store out) in the condenser.
    The knee jerk reaction to low head and low suction is to add refrigerant. Simply touching the liquid line should tell if low refrigerant is the problem. Cool line, probably not low, hot line, maybe low. Putting on the gauges should not in most cases be the first thing to do.

    Language can be problematic at times. Low subcooling for example. Does low mean a low amount of subcooling? In other words a warm LL or does low mean a cool LL =lots of subcooling, a cooler LL?
    Example when describing a problem and saying the subcooling is low. Always a question of what that means.
    I once took a test long ago with this question. "What would be suspect when measuring low subcooling.?" I wrote I couldn't answer the question the way it was written. I would rather see a term like "A warm LL or a cool LL."
    Am I the only one with this linguistic problem?
    BTW it looks like a good article.
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  8. #5
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    I would take it as just that.... the subcooling is low. The value itself is lower than it should actually be. I mean, how do you determine if a liquid line is actually warm or cool? You compare it to the condenser saturation temp..... if you dont do that you are guessing. The outdoor conditions vary so much that you can not truly say if its warm or cool. If every system in the world ran a 110* condenser saturation at any given time then yes you could probably get a feel for it. Just my 2 cent

    Quote Originally Posted by hvacker View Post
    One way to look at high head is it represents work being done. If the refrigerant is restricted the system won't do the work it normally would.
    If the refrigerant isn't moving, like Core-d wrote, it will stack (accumulate, store out) in the condenser.
    The knee jerk reaction to low head and low suction is to add refrigerant. Simply touching the liquid line should tell if low refrigerant is the problem. Cool line, probably not low, hot line, maybe low. Putting on the gauges should not in most cases be the first thing to do.

    Language can be problematic at times. Low subcooling for example. Does low mean a low amount of subcooling? In other words a warm LL or does low mean a cool LL =lots of subcooling, a cooler LL?
    Example when describing a problem and saying the subcooling is low. Always a question of what that means.
    I once took a test long ago with this question. "What would be suspect when measuring low subcooling.?" I wrote I couldn't answer the question the way it was written. I would rather see a term like "A warm LL or a cool LL."
    Am I the only one with this linguistic problem?
    BTW it looks like a good article.

  9. #6
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    Quote Originally Posted by ioncube View Post
    @ http://www.achrnews.com/articles/891...-of-the-puzzle

    I am unclear on this portion where the writes states (bold part)



    I mean if machine's metering device is constricted/clogged ..sure compressor discharge gonna rise?
    Many people think the pressure will rise but actually what happens is the gas condenses to a liquid. Liquid takes up MUCH less space than gas so that's why the pressure will drop unless of course techs keep adding refrigerant because they think it is low.

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