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  1. #1
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167

    404A Walk-Cooler

    You guys will have to excuse the ignorance of basically an HVAC guy who has been thrust into the position of doing a good bit of reefer work. I have a 404 walk in cooler where the temp is hovering slighlty above 50 degrees box temp. I took this call at the end of the day and all I have done thus far is checked my pressures and will return tomorrow. I haven't taken any line temps or any other measurements thus far. My low side pressure was 45 and high side was 175. The only medium temp coolers I worked on a few years ago were R22 units. Are these pressures in the range of what you guys normally see for 404 med temp coolers? There also is no service port for me to check pressure at the evaporator on this unit.

  2. #2
    Join Date
    Oct 2008
    Location
    Canada
    Posts
    83
    They seem low, check pressure at the compressor, unless there's a long distance between the evap and the cond unit it should get you close enough. your pressures are low, 200-225/55-60 would be closer 90* SCT would be 200psig and 25* SST would be 60ish
    **I think... I don't have a pt chart infront of me**

  3. #3
    Join Date
    Feb 2010
    Location
    butler pa
    Posts
    1,073
    Quote Originally Posted by Jettmac View Post
    They seem low, check pressure at the compressor, unless there's a long distance between the evap and the cond unit it should get you close enough. your pressures are low, 200-225/55-60 would be closer 90* SCT would be 200psig and 25* SST would be 60ish
    **I think... I don't have a pt chart infront of me**
    sounds low on charge to me also..id be looking for 55-60# suction..
    do a quick pumpdown on condenser and watch sightglass..you should see
    it pumpdown thru the glass..

  4. #4
    Join Date
    Mar 2007
    Location
    tx
    Posts
    1,088
    What was the ambient temp? Does this unit have fan cycling or head master? After you try the pump down with the king valve, if it seems you have plenty of freon, check low ambient controls. (IF it was really cold outside of course)

  5. #5
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Ambient was 60 today. I had a 6 degree TD at the evap. What was throwing me off somewhat was a clear sight glass with the occasional bubble although I know you cant tell much by that with the blends. I haven't tried pumping it down yet. Tomorrow will be cold and rainy on the roof top and im not looking forward to fooling with this thing. Thank yall for any advice you can give me. I will post more info after tomorrow.

  6. #6
    Join Date
    Jul 2007
    Location
    alexandria va
    Posts
    138
    with 175 head 50 box temp i would expect suction to be low 30s to 20s. ice would be on the first couple of bends of the coil. do u have a sight glass? 45 is high at 50 and 175 head. u may have a weak pump but we need more info. jbb

  7. #7
    Join Date
    Mar 2007
    Location
    tx
    Posts
    1,088
    Yea, we really need to know more before we can help much. 60* is low temp for trying to condense. Look to see if what kind of low ambient control we have.

  8. #8
    your pressures are low. Checked your super heat at the compressor since u said u have no service ports on the evap. some bubbles i could understand if u have no low amb controls. start with your superheat and go from there , your valve may be undersized or pinched off or out of the TXV capicty with such low head pressure. disconnect fans and watch ur head pressure and sight glass. 404 u disconnect fans and the head pressure sould climb to 400 plus quickly if it has a full charge. need more info please

  9. #9
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Ok this is what Ive got. This is a walk in cooler that has an entrance to the freezer as well. This is in a Dennys Rest. and it has glass doors that they open to access shelves inside the walk in. The glass doors do not close well and one is usually cracked open from not closing all the way. I have no model numbers for the condensing unit as they have been painted over. The model number to the evap coil is:
    HeatCraft model TLL090BE
    I added freon today going by what the other guys said normal pressures should be on a med temp 404 cooler even though the sight glass was cleared at lower pressures.
    My low side pressure is 55 with a 53 degree line temp at the compressor giving me 34 degrees of SH. My high side pressure is 225 I think because my needle started vibrating badly and hasnt stopped thus is why Im guessing here. The outside ambient is 40 degrees. The box temp is now 46 degrees and I have a 6 degree TD at my evap coil. I cant get the box to go any lower in temp. I know I have a starved evaporator but now my problem is I don't know if I still need to add freon or if I have a bad expansion valve. I do not have a service port at the evaporator. All coils have been cleaned. I appreciate you guys for helping me out and advising me.
    Last edited by hackmaster; 02-24-2010 at 04:01 PM.

  10. #10
    Join Date
    Feb 2006
    Location
    Phoenix,AZ
    Posts
    2,848
    Glass is clear. Don't add gas. It aint gonna do anything. Recover what you put in it. And open the TXV.

  11. #11
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,416
    Quote Originally Posted by hackmaster View Post
    Ok this is what Ive got. This is a walk in cooler that has an entrance to the freezer as well. This is in a Dennys Rest. and it has glass doors that they open to access shelves inside the walk in. The glass doors do not close well and one is usually cracked open from not closing all the way. I have no model numbers for the condensing unit as they have been painted over. The model number to the evap coil is:
    HeatCraft model TLL090BE
    I added freon today going by what the other guys said normal pressures should be on a med temp 404 cooler even though the sight glass was cleared at lower pressures.
    My low side pressure is 55 with a 53 degree line temp at the compressor giving me 34 degrees of SH. My high side pressure is 225 I think because my needle started vibrating badly and hasnt stopped thus is why Im guessing here. The outside ambient is 40 degrees. The box temp is now 46 degrees and I have a 6 degree TD at my evap coil. I cant get the box to go any lower in temp. I know I have a starved evaporator but now my problem is I don't know if I still need to add freon or if I have a bad expansion valve. I do not have a service port at the evaporator. All coils have been cleaned. I appreciate you guys for helping me out and advising me.
    Is the glass before or after the drier?

    Are you able to take a pressure drop reading across the drier?

    Before making ANY further adjustments, pump the system down and check the TXV inlet strainer. Go ahead and burn in a schraeder or put in a swivel tee for pressure readings. While you've got it down, don't forget to change the drier, too, just in case.

    If the unit has a headmaster, things are going to get a little tricky later, but hang with me for now.

    Now, go have lunch. Let things stabilize.

  12. #12
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,416
    Sorry, I inadvertently posted that before I was done...

    Anyway. Make sure you have a full sightglass. Get a pressure at the evap and take your temp there, too. For a walk-in box, shoot for about a 6-8 degree superheat. Don't worry about frost lines, just take the pressures and temps.

    Now, I mentioned headmasters before. They are a biit fiddly to charge correctly.

    http://www.sporlanonline.com/90-30-1.htm

    Read this twice. Print it. Laminate it. Follow the directions TO THE LETTER. You'll be golden on charge.

  13. #13
    if your sight glass is after the drier, i would set up your gauges at the compressor and set ur meter up to take the line temp. then id start opening your TXV and see what your pressures do. by opening the TXV, your low side pressure should increase and if u open it enough your superheat will start to come closer together. when u begin to open that valve and your pressure rises on the low side, if ur low on freon u will see bubbles in the glass because your flowing more freon. those are all great ideas to change drier and put a service port but from what im reading it sounds like ur in a hurry, and thats time consuming. Even if u get your refrigeration operating with in ideal pressures and superheat, your box temp will not fall quickly if its full of product.

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