having trouble with R22 walk in cooler - Page 2
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  1. #14
    Join Date
    Feb 2004
    Location
    Maine
    Posts
    483
    Referdude asked what was controlling the temp, thermostat in box or pressure switch on suction. I feel he asked an excellent question here. No matter how well that unit is set up and running if your controls aren't right you won't hold the proper temp in the box. Just a thought

  2. #15
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    a low pressure cutoff is controlling the unit set at 32out and 64 in, and a timer to shut unit down for 60 min twice a day leaving the evap fan running, i left the timer settings alone cause manager said defrosting was never a problem, unless systems with different refrigerant require different defrosting settings

    i charged unit to clear sight glass, i dont know why i didnt think of that before, i was more worried about the pressure, i got the discharge up to 230psi and suction went up to 60 and with a little tinkering of the txv adjuster the super heat at the coil is down to 9 i got 22 after the txv into the inlet tube of the coil and 31 at the outlet tube just before the txv bulb, but because both lines are attached the rest of the way to the compressor im getting 64 degrees at 60psi at the compressor.

    all tubes are now condesating in the evaperator compared to only the first row which i had yesterday, so hopefully it was just undercharged, i gotta back in a couple of hours and check on it.

    i was just worried that the pressure at the compressor reading 68 after charging to a clear sight glass it wouldnt cool the box enough, its practically a normal house AC system but the suction eventually dropped to 57,and the discharge stayed at 230

    hopefully i can get a check and move on the the next one now

  3. #16
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    ok all seems well now box is holding 38 degrees with constant door opening all day long

    im gonna check it again first thing in the morning before antone gets there, if box get down and holds 35 all is well, if it still holds 38, can adjusting the txv fix this and if so would you think to alow more liquid in or less,

    would you say my LPC settings are right 32out and 64in for R22

    pressures were at 38 suction 245 discharge,box at 38 degrees, the coil temp im not sure of didnt wanna move 14 gallons of milk again to take off the side panel but all seems fine now, just might need so minor tweaking to get to 34-36 degrees inside the box

  4. #17
    Join Date
    Jan 2004
    Posts
    27
    did you check the filter screen in the txv? could be clogged.

  5. #18
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,249

    Just some advice here.........

    1. Stop playing with the TXV as if it were a pressure regulator. Its only function is to control evaporator superheat and that's all it knows.

    2. Since you're asking about low pressure control settings to control temperature I assume that you have no thermostat or liquid line solenoid valve for pumpdown. A LP control is good for temperature control in a deli case but not in a walk-in box.....especially with R22. If your boss expects you to do what's right to make this system run work, add a LLS and thermostat for temperature control. Then you won't be married to this box.....and its owner.

    3. If you're looking for 34-35 Deg F box temperature you'd best add a defrost timeclock to the above stuff if you don't want to be called back for a frozen-up evaporator.

    If this came across as harsh commentary, I apologize. I have seen so many jobs where somebody came in and messed it up royally and didn't care afterward. I commend you for bringing this problem of yours to us here and trying to get the straight info to do it right.

  6. #19
    Join Date
    May 2004
    Posts
    11,937
    He has a time clock on it but it is set to 60 min x 2 a day. I would like to see 4 x 30 and others would like to see 2 x 30 @ 12 & 12.

    The LPC set at 32 and 64 is off. That would equal 10* shut down and 37* turn on. But you have to consider the subcooler effect on the line set too.

    Like Ice said. A walk in cooler is no place for a LPC to control temp. Set it at 5 lb cut out and 25 cut in. Install a 120v pump down solenoid and thermostat at the evaporator. Take the 120v power from the fan power supply, run it to the coil and then to the thermostat and back to common. Don't let the fans cycle with the stat. As the stat opens, the valve closes and the LPC will shut down the unit.

    Since your time clock in on the top of the walk in, have the clock make and break the LLV as well. Just two little ol wires

    I agree with ice, leave that TXV alone now. Let it do its job. If you haven't insulated the TXV bulb, do it now. It is time to work on the control system and make it a real walk in. That'll impress'em.

    No one has discussed your billing for your labor. You addressed it a little but with a customer that has product loss and you are doing "OJT" I would think you would want to reflect a normal billing time. Not sure how others will react but 5 to 7 hours should be close. Another thing, I would suggest doing the stat and LLV at no charge to show him you are looking out for his needs and want to keep him as a customer. (These are my thoughts only and reflect the nature of the beast but not those of your BOSS) if you know what I mean.

    Oh yeah... welcome to the site.

  7. #20
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,249
    Jeeez.....I wish I had had this kind of educational resource when I was stumbling around in the dark 35 years ago.

  8. #21
    Join Date
    May 2004
    Posts
    11,937

  9. #22
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    hey everyone thanks for your input, i am so glad i found this site and will recomend many to stop by, i dont think im gonna go with the pump down controll on this one not beause i dont want to do it right but because there was never one before and i spent to much time allready and i have no clue to what the hell it is and how it works, i got the cooler to 38* its 100 better than what i started with. i will install a tstat though, and adjust the timer for defrost, but i will definatly look into the upcoming seminars on refrigeration and freezer apps at the local supply houses here in chicago, this was my first time on a cooler i have only done residential HVAC prior and learned on the job half ass i guess, and figured out a lot after learning on the job then going to school, i never knew about SH and SC my boss always just felt the heat coming off of the condenser fan motor but learning on the job then going to school is a way better benefit than going to school and then out in the field

  10. #23
    If you are going to install a tstat set the LP control as a safety say 55/35. I would suggest 4 def per day and start at 30 min. If you choose not to go with the tstat I would set the LP to 58/38 and the adjust the cut out to get the box temp you want (35) Just be aware that with LP control changes in the weather and the condition of the condenser will affect compressor capacity and you will most likely on occasion get calls that the box is too warm or everything froze.

  11. #24
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    Originally posted by refer dude 2479
    If you are going to install a tstat set the LP control as a safety say 55/35. I would suggest 4 def per day and start at 30 min. If you choose not to go with the tstat I would set the LP to 58/38 and the adjust the cut out to get the box temp you want (35) Just be aware that with LP control changes in the weather and the condition of the condenser will affect compressor capacity and you will most likely on occasion get calls that the box is too warm or everything froze.
    the condensor is in the kitchen on top of the box with constant ambient at like 90 degrees, butt i am going to install tstall and will adjust the defrost timer hopefully this will solve problem for a least a 6 month call back, this is a complete learning experience for me but thanks for all your input

  12. #25
    Join Date
    Jun 2004
    Location
    MidWest
    Posts
    64
    If you put a T-stat in, trust me, you will want to install a LLSV (Liquid Line Solenoid Valve) or you will be back in a month or less. You can get the valve body to your LL size then, I believe it was Lusk, like he said get a 120v coil. It's 2 seperate pieces for the part. Talk to Johnstone they should know what it is and help you. Leave the LP control in it will still control your compressor operation. The customer might be happy now but if it goes down again due to an iced up coil within a couple weeks you will be right back where you started if not worse with your customer.

  13. #26
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by icemeister
    Jeeez.....I wish I had had this kind of educational resource when I was stumbling around in the dark 35 years ago.


    Line-jacker.


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