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  1. #14
    Join Date
    Apr 2012
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    winnipeg
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    Quote Originally Posted by craig1 View Post
    Its actually more complicated than that. When you reduce capacity, you reduce the work being done by the compressor, which in turn reduces its amp draw. So even if the restricted line causes a 3% capacity reduction, efficiency reduction might only be 1% or even nothing.
    under sized suction lines cause a capacity loss and hi velocity.....
    it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair

  2. #15
    Join Date
    Aug 2004
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    North Richland Hills, Texas
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    14,914
    Quote Originally Posted by craig1 View Post
    Its actually more complicated than that. When you reduce capacity, you reduce the work being done by the compressor, which in turn reduces its amp draw. So even if the restricted line causes a 3% capacity reduction, efficiency reduction might only be 1% or even nothing.
    I was just pointing out that you do in fact lose efficiency, not attempting to exactly quantify the efficiency loss.

    Continuing the discussion though, when you are dealing with total system capacity losses due to pressure losses, and other issues within the system, the electrical consumption per btuh of net refrigeration usually doesn't go down, or even stay the same.
    Typically it will go up.

    Either way, in most instances the small efficiency loss, due to the small capacity loss incurred by having the smallest recommended vapor line for the application, isn't worth the cost of replacing the refrigerant lines.
    If more government is the answer, then it's a really stupid question.

  3. #16
    Join Date
    Oct 2010
    Location
    AZ
    Posts
    646
    Quote Originally Posted by carmon View Post
    under sized suction lines cause a capacity loss and hi velocity.....
    Quote Originally Posted by mark beiser View Post
    I was just pointing out that you do in fact lose efficiency, not attempting to exactly quantify the efficiency loss.

    Continuing the discussion though, when you are dealing with total system capacity losses due to pressure losses, and other issues within the system, the electrical consumption per btuh of net refrigeration usually doesn't go down, or even stay the same.
    Typically it will go up.

    Either way, in most instances the small efficiency loss, due to the small capacity loss incurred by having the smallest recommended vapor line for the application, isn't worth the cost of replacing the refrigerant lines.
    Quote Originally Posted by craig1 View Post
    Its actually more complicated than that. When you reduce capacity, you reduce the work being done by the compressor, which in turn reduces its amp draw. So even if the restricted line causes a 3% capacity reduction, efficiency reduction might only be 1% or even nothing.
    Yes, it is more complicated than that. Remember pump laws and fan laws state that when you block flow, the amp draw is reduced. How much would be hard to determine and you may gain/lose efficiency or stay the same. Calculations for this stuff are just estimations, and you would really have to test it and get real numbers and plot an efficiency curve to find out. But with such a small difference, it doesn't really make sense to worry about. There are a lot of other things that can make a bigger difference, one being orientation and location of the condenser to minimize solar radiation effects which can raise the head pressure considerably and drop efficiency.
    Last edited by dijit; 02-16-2013 at 05:06 AM. Reason: grammar

  4. #17
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,074
    Quote Originally Posted by dijit View Post
    Yes, it is more complicated than that. Remember pump laws and fan laws state that when you block flow, the amp draw is reduced. How much would be hard to determine and you may gain/lose efficiency or stay the same. Calculations for this stuff are just estimations, and you would really have to test it and get real numbers and plot an efficiency curve to find out. But with such a small difference, it doesn't really make sense to worry about. There are a lot of other things that can make a bigger difference, one being orientation and location of the condenser to minimize solar radiation effects which can raise the head pressure considerably and drop efficiency.
    Solar radiation doesn't have much effect either. unless the condenser is on a roof, or other surface that is reflecting both radiant heat and convection heat.
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