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  1. #1
    Join Date
    Nov 2011
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    Moreno Valley Ca.
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    10

    Confused Proper/best way to to charge 60dg walk in cooler R-404a

    Working on a Copeland R404a 5x7 walk-in cooler maintaining 15C/59F. Have been getting mixed advice on charging techniques. I normally charge to subcooling specs and 20-40dg compressor SH. Am confused about the 10-20dg TD charging rule and how to use it. I understand all freezers have a 10dg TD and Medium to High temp use 15-20 TD Can someone please explaine? Thanks in advance

  2. #2
    Join Date
    May 2009
    Location
    San Diego
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    10
    So many variables......I've really only seen the subcooling method applied to R410a, but thats another story. R404a......Charge with liquid to a full glass. No glass, 30dg over ambient. 10dg subcooling (optimal). As far as heat abortion "superheat"....freezer 7-9, cooler 10-12, a/c 12-15.
    Copeland says 30dg......sounds high to me, but they're the engineers.
    Hope that helps

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
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    25,551
    Tell me more about this unit...

    A 5x7 box maintaining 60 degrees? What purpose?

    Does it have a receiver? Is the condensing unit outdoors? Is it a pumpdown unit?


    Now, ASSUMING that it has a receiver, I'll make the following suggestion.

    Charge to a clear sightglass.

    Taking it further.

    IF the condensing unit is indoors, I'd add a small amount of refrigerant to handle temperature fluctuations.

    IF the condensing unit is outdoors, there's a whole nother bit of calculations that are required to properly charge the unit.

  4. #4
    Join Date
    Nov 2006
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    Southeastern Pa
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    18,272
    Quote Originally Posted by Ken11 View Post
    Working on a Copeland R404a 5x7 walk-in cooler maintaining 15C/59F. Have been getting mixed advice on charging techniques. I normally charge to subcooling specs and 20-40dg compressor SH. Am confused about the 10-20dg TD charging rule and how to use it. I understand all freezers have a 10dg TD and Medium to High temp use 15-20 TD Can someone please explaine? Thanks in advance
    That is a great question, but I'd like to see you post it in the Pro forums. Get you post count up to 15 (only 12 posts to go) and we can answer that question.

    Hint: in refrigeration, the "TD" value uses the evaporator suction saturation temp, and in air conditioning, we use delta T, or the return air temp versus the supply air temp. It's a different approach to the subject.
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  5. #5
    Join Date
    May 2011
    Location
    Spring City, Pennsylvania, United States
    Posts
    190
    Crossthread- you are talking about sh taken at the evap, which is how it should be set on reefer system. Copeland cares about comp protection.

  6. #6
    Join Date
    Oct 2011
    Location
    Chicagoland Area
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    Quote Originally Posted by crossthread View Post
    So many variables......I've really only seen the subcooling method applied to R410a, but thats another story. R404a......Charge with liquid to a full glass. No glass, 30dg over ambient. 10dg subcooling (optimal). As far as heat abortion "superheat"....freezer 7-9, cooler 10-12, a/c 12-15.
    Copeland says 30dg......sounds high to me, but they're the engineers.
    Hope that helps
    This should be in the ARP forum.
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  7. #7
    Join Date
    May 2011
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    Spring City, Pennsylvania, United States
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    Quote Originally Posted by 2sac View Post
    This should be in the ARP forum.
    Man can't believe I missed that! Maybe in the aop roe v wade section

  8. #8
    Join Date
    Mar 2009
    Location
    Mid-Mo
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    Quote Originally Posted by jpsmith1cm View Post
    Tell me more about this unit...

    A 5x7 box maintaining 60 degrees? What purpose?

    Does it have a receiver? Is the condensing unit outdoors? Is it a pumpdown unit?


    Now, ASSUMING that it has a receiver, I'll make the following suggestion.

    Charge to a clear sightglass.

    Taking it further.

    IF the condensing unit is indoors, I'd add a small amount of refrigerant to handle temperature fluctuations.

    IF the condensing unit is outdoors, there's a whole nother bit of calculations that are required to properly charge the unit.
    ^^
    Ya that....

  9. #9
    Join Date
    Nov 2011
    Location
    Moreno Valley Ca.
    Posts
    10
    Ok will post in ARP forum, sorry. As for crossthrreads response to charge to a full sight glass, hmmm.... not too sure bout that. R-404a series refrigerants should never be charged to full sight glass based on research from this exact same problem. The first time I did just that and unit was overcharged. I believe i read that in Danfoss refrigeration basics or something. I will find and post. But i never really got an answer as to why you shouldnt charge this series to full glass. Is it due to blend, fractionization capabilities, pressure drop??

  10. #10
    Join Date
    Sep 2008
    Location
    Western PA
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    25,551
    Quote Originally Posted by Ken11 View Post
    Ok will post in ARP forum, sorry. As for crossthrreads response to charge to a full sight glass, hmmm.... not too sure bout that. R-404a series refrigerants should never be charged to full sight glass based on research from this exact same problem. The first time I did just that and unit was overcharged. I believe i read that in Danfoss refrigeration basics or something. I will find and post. But i never really got an answer as to why you shouldnt charge this series to full glass. Is it due to blend, fractionization capabilities, pressure drop??
    If you've got a receiver, clear the glass.

    Don't care what the refrigerant number is.

    Systems without a receiver are a different animal entirely.


    Typically, walk in equipment has a receiver, so clear the glass.

  11. #11
    Join Date
    Sep 2008
    Location
    Western PA
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    25,551
    Ken11,

    They were joking a bit with you about a misspelling in your post.

    Issues like Art, Religion and Politics belong in ARP...

  12. #12
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,551
    http://sporlanonline.com/90-30-1_072012.pdf


    Here are Sporlan's charging recommendations.

    Reading them carefully, I see NO mention of leaving bubbles in a sightglass for 400 series refrigerants.

  13. #13
    Join Date
    Mar 2009
    Location
    Mid-Mo
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    3,595
    Quote Originally Posted by Ken11 View Post
    Ok will post in ARP forum, sorry. As for crossthrreads response to charge to a full sight glass, hmmm.... not too sure bout that. R-404a series refrigerants should never be charged to full sight glass based on research from this exact same problem. The first time I did just that and unit was overcharged. I believe i read that in Danfoss refrigeration basics or something. I will find and post. But i never really got an answer as to why you shouldnt charge this series to full glass. Is it due to blend, fractionization capabilities, pressure drop??
    I guess you're telling me jp has lied to me this whole time!! Guess I have been doing it wrong this whole time and have every refrigeration system I have worked on charged incorrectly....

    Love to see where you are basing your information from!

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