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  1. #1

    Walk-In Freezer R404A

    Started Charging a R404A Walk-In Freezer, ambient temp was 30 degrees. HS 155 PSIG< LS 11PSIG. I've read where this website talks about condensing Temp of Ref must be at 105 degrees when doing low ambient charging. My problem was even blocking the condenser couldn't get the 105 degree cond temp with probe located at outlet of king valve.(Temp would only get to 75 degrees). FLA on comp was almost loaded 10.7 FLA running at 10.0 amps. Superheat was high but only if I shut off the condenser fan could I get the condensing temp up. Then operation of TXV sporadic. Just trying some info I read on this site. Box temp good around 0 degrees. I added ref 8 lbs and no change in liquid line temp...?

  2. #2
    Join Date
    Jan 2006
    Near Atlanta, GA.
    Those pressures are way low. Three questions...

    1-Do you have a site glass
    2-Is there any type of head pressure regulator such as Headmaster (hopefully) or fan cycle
    3-What is your ambient temp

  3. #3
    Join Date
    Jul 2002
    What was the reason to add gas? Did you liquid charge? What was the subcool and superheat?
    Not what it use to be

  4. #4
    Read "Ks" comments about headmasters then go here.

  5. #5
    Join Date
    Jul 2000
    Guayaquil EC
    Quote Originally Posted by leathernecke5 View Post
    ....I've read where this website talks about condensing Temp of Ref must be at 105 degrees when doing low ambient charging. My problem was even blocking the condenser couldn't get the 105 degree cond temp with probe located at outlet of king valve.(Temp would only get to 75 degrees)....
    The thing about getting the condensing temperature up during low ambient charging is for systems with a Headmaster type condenser flooding control and a liquid line sightglass. It appears your system has neither.....and it needs both if it's ever going to run right. A condenser fan control would help, but it doesn't look like you have one of those either.

    Also....when we refer to condensing temperature we're not talking about the liquid line temperature, rather it's the saturation temperature corresponding to the condenser, with that 155# high side pressure on R404A my PT chart tells me your condensing temp is 72F. You use the line temperature to calculate your liquid subcooling.

  6. #6

    R404A Walk-In Freezer

    Let me first say thank-you for the responses. Now the sight glass is full and upon reading the info about condensing temp which trying to get the system to a 105 degree condensing temp which would be PSIG of 250 about, if I understand the Heatcraft info I read. I couldn't attain that. The system has a headmaster control and what surprised me was even blocking off the condenser didn't raise the HS pressure only after shutting off the Cond Fan could I raise the pressure simulating higher ambient conditions. The superheat is way high as in 30 degrees or more. My experience has been that these pressures were low and it puzzled me as to blocking the condenser pressure didn't go up. Theory being condenser not very full. The Headmaster makes things a little unique in charging. I didn't attempt to adjust superheat yet as I'm not satisfied with the charge yet. Box temp is about 0 degrees with dual evaps.

  7. #7
    Join Date
    Jan 2007
    Washington State

    Try This

    I've run into this very situation when charging a system from scratch. The reason you can't get the head up is because you don't have a load. The reason you don't have a load is because all of the gas is stuck behind the headmaster in the condenser. This is also why you have such a high superheat. I bet you are charging this through the liqid line hugh? Try charging the system through the suction port with the condenser fan off. If you have a sight glass you can actually watch he headmster open. There should be a stamp on the valve that indicates what it pressure setting is. For 404a it's probably around 180psig. The valve will begin to open slightly before that pressure and will then go to full open. Your superheat will come down and your head will settle out. Good luck

  8. #8

    R404A Walk-In Freezer

    Thank-you Mr.Fixit and I agree with that due to when charging in an attempt to increase my condensing temp I disconnected the condenser fan and almost immediately my liquid line temp started to rise indicating what I believe is the Headmaster responding. The Superheat is high. I was going to attempt the adjust the Superheat on the TXV's due to it being so high but maybe just disconnect condenser fan and monitor operation. When Headmaster started to open bubbles appeared in sight glass. Again Superheat is high at the Evaporators which needs to be addressed..Again Thank-you Sir..

  9. #9
    Join Date
    Jan 2006
    DFW Metroplex
    How many lbs are in the system, do you have a guess?

    Is there a nameplate that indicates 90% charge?

    MN of compressor?

  10. #10
    Join Date
    Jan 2007

    What is the make ?

    This does not happen to be a Russel High Sierra ? If it is, its somewhat diffrent and it is designed to work on low head pressure.. If it is let me know and ill get into more detail..

  11. #11
    Join Date
    Feb 2007
    with a full sight glass on 404 in low ambient conditions and a headmaster, the HM should bring the pressure up to the lable (180-210) on the HM. The reason that the pressure doesn't change while blocking the condenser is because the condeser is already partially flooded from the HM, reducing the surface area of the condenser. I'd look at a faulty head master to start. you might also try opening up your TXV, it could be starving and not picking up much heat.

  12. #12
    what is your system superheat and what is the superheat across each evap coil?
    Start there.

    I agree that you may have a bad hm since you have to drop out the cond fan in order to raise your head pressure.
    On a working system in that ambient, (30F), you should be running the cond fan and NOT experience bad performance.

    (I'm not really adding anything useful to this thread, I'm just running up my post count

    (Besides, I gotta do something while I'm sitting in my wife's room at the hospital. They're keeping her overnight... )

  13. #13
    Let me say thank-you for the input. I posted on Pro Forum topic Explain This. But here is update for those interested. Yesterdy the ambient temp was 30 degrees. I checked Superheat at both Evaps and found SST 15#= -25 degrees LS pressure at Suction filter port. I checked Superheat at evap #1 and found temp at sensing bulb 5 degrees giving me 30 degree superheat, check evap #2 and found temp at sensing bulb 10 degrees giving me 35 degree superheat. I attempted to adjust valves but to know evail in correcting superheat problem at evaps. I check compressor superheat just out of curiosity and found 15# on low side equalling -25 degree SST and temp at compressor 6" -9degrees. Uh how can I have starving evap and a low superheat at compressor. Low Side pressure is the same at outlet of evaps, suction filter port and Suction Service Valve. When I disconnected the condenser fan motor and watched my Liquid Line Temp go up I immediately saw bubbles in sight glass. I believe you guys are right in my condenser was full and storing all my ref. I'm going to try a fan cycling control and monitor the results. I think my condensing temp way to low thereby starving the coil(evap) and creating no load at the compressor.

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