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  1. #1
    Join Date
    Oct 2002
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    Lexington, NC
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    5,137

    Saturated Suction Temp-REF PLUS BRAND

    I am pretty sure this is correct, but I need to verify. I am having to study this manual for a test.
    Is the saturated suction temperature the same as the evap coil temp?
    Ie. on some of the manufacturers spec sheets, they will show coil temp and some will show saturated suction temp.
    Also, what does the abbreviation FTD stand for? Is this freezer temp difference or fahreneheit temperature difference?

    Also, in this manual on page 4 and the other sizing pages, the is a fine print note that states" For 4 fpi, multiply capacity by 0.8". What is this refering to?
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  2. #2
    Join Date
    Jul 2000
    Location
    Guayaquil EC
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    10,259
    Quote Originally Posted by nchvac View Post
    I am pretty sure this is correct, but I need to verify. I am having to study this manual for a test.
    Is the saturated suction temperature the same as the evap coil temp?
    Ie. on some of the manufacturers spec sheets, they will show coil temp and some will show saturated suction temp.
    Basically, yes...it's referring to the same thing. In reality however, if you consider the pressure drop in the suction line between the evaporator and the compressor suction they will differ by that pressure drop's equivalent temperature.

    Quote Originally Posted by nchvac View Post
    Also, what does the abbreviation FTD stand for? Is this freezer temp difference or fahreneheit temperature difference?
    That's referring to the TD or temperature difference between the box temperature and the evaporator temperature and is usually written as F TD. For example a 35F box with an evaporator temp of 25F would have a 10F TD.

    Quote Originally Posted by nchvac View Post
    Also, in this manual on page 4 and the other sizing pages, the is a fine print note that states" For 4 fpi, multiply capacity by 0.8". What is this referring to?
    The term "fpi" refers to the number of "fins per inch" of the coil. The less fins per inch, the lower the coil capacity, so they give you a capacity derating factor for fin spacings other than the standard one listed. In this case, if you were using a coil with 4 fpi, you would multiply the published capacity by 0.8 to arrive at the coil capacity.

  3. #3
    Join Date
    Oct 2002
    Location
    Lexington, NC
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    5,137
    So we lower the capacity for less fins per inch due to a lower conduction factor. Are they still selling the 4 fpi coils, or is this in a situation when you would change the condensor section only and leave the old coil?
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  4. #4
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,137
    One other thing that I am trying to understand is why you add to the btu removal rating of the evaporator by adding for the fan. Is it because of the fan speed varying from each style of fan?
    I first thought that they were adding in for the need to remove the fan motor heat, but it seems that you would have to subtract from the btu rating of the space in order to account for the heat of the motors. Are they saying to add the x amount before you pick out your evap coil (the way it seems it should be)? It sounds to me like they may be saying to add x amount of btu to the coil capacity. This doesn't seem right. It seems like it would be added in to the load before choosing the coil.
    Help me to understand what they are asking the designer to do here.
    Thanks

    Here is how it is worded:
    1. Operating charge based on 30% liquid and 70% vapor at 25F suction
    2. Fan Motor heat is not included in rating
    Unit 0601 to 2001 and 2401, add for Shaded Pole motor (58W) 198 BTU/HR
    Unit 2101 and 2801 to 4201, add for PSC motor (100W) 342 BTU/HR
    Unit 2101 and 2801 to 4201, add for EC motor (60W) 205 BTU/HR
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  5. #5
    Join Date
    Jul 2000
    Location
    Guayaquil EC
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    10,259
    Quote Originally Posted by nchvac View Post
    So we lower the capacity for less fins per inch due to a lower conduction factor. Are they still selling the 4 fpi coils, or is this in a situation when you would change the condensor section only and leave the old coil?
    The selection of the FPI usually comes about at the design stage of a project, where you're selecting compoinents and matching them up.

    4 FPI would typically be used for a low temperature evaporator coils. The wider spacing allows for frost buildup. Evaps for medium temp applications usually run 6-8 FPI. Condensers might be more like 8-12 FPI.

  6. #6
    Join Date
    Jul 2000
    Location
    Guayaquil EC
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    10,259
    Quote Originally Posted by nchvac View Post
    One other thing that I am trying to understand is why you add to the btu removal rating of the evaporator by adding for the fan. Is it because of the fan speed varying from each style of fan?
    I first thought that they were adding in for the need to remove the fan motor heat, but it seems that you would have to subtract from the btu rating of the space in order to account for the heat of the motors. Are they saying to add the x amount before you pick out your evap coil (the way it seems it should be)? It sounds to me like they may be saying to add x amount of btu to the coil capacity. This doesn't seem right. It seems like it would be added in to the load before choosing the coil.
    Help me to understand what they are asking the designer to do here.
    Thanks

    Here is how it is worded:
    1. Operating charge based on 30% liquid and 70% vapor at 25F suction
    2. Fan Motor heat is not included in rating
    Unit 0601 to 2001 and 2401, add for Shaded Pole motor (58W) 198 BTU/HR
    Unit 2101 and 2801 to 4201, add for PSC motor (100W) 342 BTU/HR
    Unit 2101 and 2801 to 4201, add for EC motor (60W) 205 BTU/HR
    I can't recall ever seeing ratings that didn't account for the fan motor heat in the capacity. Whose product info are you looking at?

  7. #7
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,137
    Ref Plus is the brand. I don't know much about it. I was given it to study for a refrigeration exam
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  8. #8
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,259
    Quote Originally Posted by nchvac View Post
    Ref Plus is the brand. I don't know much about it. I was given it to study for a refrigeration exam
    That's one I've never heard of either, but here it is:
    http://www.refplus.com/html_en/produ...-LP-LA2009.pdf

    Nobody else rates unit coolers like that...at least that I'm aware of.

  9. #9
    Join Date
    Jun 2001
    Location
    Michigan
    Posts
    12,077
    i think it's awesome your being taught this in your school. maybe the ole boy from Ohio who is an instructor should be in that course your taking.

  10. #10
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,137
    I called tech support. I found out that you add the fan load that they are giving you on during your calculation. We do this anyway, but we usually do it by HP x 75000. I think this operation is in Canada. Looks like a good machine.
    To be honest with you, the most confusing design data that I have seen has been by Heatcraft. They make it a little too indepth. I hope to learn more on their units though because that is the majority of what is located around here.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  11. #11
    Join Date
    Feb 2008
    Location
    Vancouver, BC
    Posts
    41
    we are doing cooler/freezer load calculations right now in school. As for evap motors, they are added in the total BTU's. We go off of tables that were given to us by the teacher. The table is a little vague but the hp rating on the table range from 1/8hp to 30hp, then there is the BTU/hr that is rated to that hp of the motor (ie: 1/8hp is 900 BTU's/hr)

    Lets say that there are 3 motors so the calculation goes, 3 (motors @ 1/8 hp in the coil) x 900 BTU/hr x 24 (hours in a day) = 64800 BTU's

  12. #12
    Join Date
    May 2004
    Posts
    1,834
    Where do they come up with these figures? I come up with something different all together.


    1 HP=746 watts
    1 watt= 3.413 BTU
    1 HP= (3.413 x 746)= 2546 BTU

    1/8 HP=318.25 BTU

  13. #13
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,386
    Quote Originally Posted by Dowadudda View Post
    i think it's awesome your being taught this in your school. maybe the ole boy from Ohio who is an instructor should be in that course your taking.
    Are you being gruppy???

    Wait. I think that was someone else.


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