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  1. #1
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    well guys my first post here, i found this site thru google looking for info on a lil poroblem i have, iv'e spent about an hour hour and a half looking thru the forums and found tons of usefull info here, nothing quite that would help with this instance, but tons with others, i find myself sitting here long hours with a 12 pack of becks just reading up on all this info

    Any way, i have a walkin cooler that the compressor went bad in, it was a dupont mp39 system, we sold the costumer an entire new system that is R22, everything was replaced but the lineset whick was blown vacumed from the old system and blown out when the lines were cut so no oil was left in the lines or anything like that, all said and done the new condensing unit and coil are in place and brazed, a R22 txv is inplace i dont have a digital vacuum meter so once the psi om my gages read 30hg i left the pump running for at least 30 min while i had lunch, all said and done it was time to charge the unit after determinig there was no leak, now residential AC i have no problem with this the first time i actually worked on a cooler, so from what i know about R22 on residential i took to the cooler, and well i have nothing but problems, first off the customer is yelling because he thimk the cooler temp is 55 degrees because that is what his thermometer says, i proved him wrong with 3 other thermometers that i have that say the cooler is 46 degrees which still isnt cold enough they said the old system worked fine until it stopped working so when buying the new condensor and coil we used a cross refernce to the existing(old) unit from the MP39 to R 22, operating pressures are 48 suction and 160 liquid,and 75 percent of the evaporator is condensating, yet the coil is operating at 41 degrees, if i put more R22 in the system the the pressures rises and so does the temp of the cooler, if i take refrigerant out of the system, the first row of tubes on teh evaporator coil freeze and have a temp of like 17 degrees but the rest read from 37 to 58 at the suction outlet, being a cooler the pressures to my knowlege have to be less then that of residential AC to get the temp down but i cant seem to get this system working properly, the TXV is ajustable to let in more or less liquid but it doesnt seem to make a difference, the only difference is the first few tubes freezing when i change the pressure, yet that doesnt even make a difference on the acyual cooler temp, one thing i noticed with the line set is that the liquid line and suction line are sort of welded together, i know in some instances this helps, but never seen the entire line wrapped in sulation together so tomorrow im going to replace the lineset and keep the liquid line outside of the insulation and see if that makes a diference, my boss who could prolley help is on vacation this while week with any kind of comunication disabled, i dont mean to be an XXXhole but if the buisness dont at least pay for new equipment ill pull everything out of there and leave them with nothing, my time invested ill ue as a learning experience, but these guys are starting to yell at me ive been playing with this damn thing for 3 days now and im frustrating myself as well as the costomer, they dont have another cooler to use temporarily that will hold everything and are starting to complain about loss of product, i have noticed that not everyone who enters the cooler close the door when they exit but one day i arrived before anyone in the kitchen even starts working so noone was in the cooler the entire night and it still was 47 degrees in there

    sorry for this novel but i need help like now

  2. #2
    Join Date
    Jun 2004
    Location
    MidWest
    Posts
    64
    Going to need a lot more info bub. 1st off mp39(401A) is a R-12 retrofit. When you say entire system are you refering to the condensor and evap or just condensing unit. Did you change the TXV? If so did you match the tonage and make sure it is a 22 TXV?What are your existing line set sizes? What condensing unit did you use(brand and model number)? What was the tonage on the old system?

  3. #3
    Join Date
    Feb 2003
    Location
    NH & Cebu
    Posts
    1,608
    We need more info. How about model #s from the evap and condensing unit. What do you have for a TXV? What was your evap superheat? How big a box is it? Any glass doors? I'm sure others will have more questions

  4. #4
    Join Date
    Feb 2004
    Location
    Western New York
    Posts
    1,027

    Welcome Prestiege (prestige?)

    First take a big deep breath, and slow down. Then keep it to 2 or 3 Becks per night when you are posting.

    Then remember about periods and paragraphs. They may not help you, but they will help those of us who might want to help you. Trying to read that "Stream of Conscience rant", took too much work. You are not Arthur Miller. That in itself, should make you happy.

    New equipment, sized by the boss, who is now on vacation. And he didn't leave a contact number for you. I think your priority is not this cooler, but a job search.

    But here you are, and to help, the following info would be needed.

    Size of the cooler, how many doors (and kind), and usage.

    What compressor and coil (mod #) did you take out?


    What compressor and coil (mod #) did you put in?

    Things aren't right, everone is pi**ed, and you didn't make the choices. But you have to clean up the mess. Welcome to refrigeration.

    *************************************************

    SH*T Boss, just saw I'm just a "member" again. Couldn't you keep *SS* up till the deal is done? But then, another name for a member is a tool.....

    [Edited by baub on 08-11-2004 at 08:53 PM]
    Experience is what you have an hour after you need it.

  5. #5
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,080
    Is there a liquid line sightglass in this system? If there is, just charge to clear the glass and you'll basically be good to go.......all else being OK, that is. If you don't have a SG, then install one and stop having to mess around worrying about the charge so you can go on to other stuff like suction superheat.

    We'll still be waiting for your response on model numbers and such so we can give you more specific advice on this situation.

    BTW, welcome to the site!

  6. #6
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    well the box is 7 x 11 and 7 feet tall, no glass doors just aluminum panels 4 " thick with the normal foam inside, i dont have the models numbers handy,although i know its a 3/4HP compressor, but when purchashing everything , i gave the guy at supply house the old condensor model and you were right about mp39 being
    401A,thats what they said. i dont have a dupont chart nor did the supply house, they told me this was a compatible R22 replacement system going by the old condensing unit numbers, i replaced the condensing unit which sits on top of the cooler in the in the kitchen with at least 80-90 ambient and the evapotator recomemded to the condensor specs with an R22 txv, the line set is 1/2 inch and 1/4 inch. there is a SG which has no bubbles and indicates dry, i charged unit thinking if pressure exceded a freezing temp/pressure ratio it would run as a normal ac unit using R22. i never really touched a refrigerator before. the boss says stick with it and try to figure it out its the best way to learn yet the costomer screaming about lost food products isnt appiezing either

    [Edited by prestiege on 08-11-2004 at 09:59 PM]

  7. #7
    Join Date
    Jan 2004
    Location
    Earth
    Posts
    4,879
    R-22 160 pounds sounds way undercharged to me.

    Sight glass gets my vote. Set your TXV back, to half the number of turns from stop to stop.
    A Diamond is just a piece of coal, that made good under pressure!

  8. #8
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,543
    I think 250 to 275 psig is not unconmmon at 90 degrees with a warm box. Clear the sight glass and watch the superheat. but valve back to 4.5 turns from the front stop. Also did you change the oraface in the distributor at the txv outlet if you have multiple distributor lines?

  9. #9
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    ill have to adjust the valve again tomorrow right now its back to the factory setting at least i think form counting the turns

    i hadnt checked subcooling but superheat is extremly high i guess, pressure on the suction side is near 50psi(because im thinking the coil will run at near 26 degrees and thus cool the box) yet actual temp of the suction line is 70-74 at compressor, temp at txv bulb is round is like 58, i guess ill check the subcooling tomorrow, but if the discharge pressure is to low and i add refrigerant to bring it up the suction psi goes up as well, wouldnt this create a higher evap temp and make the box warmer than it already is

    what are the ideal pressures for a R22 walk in,

    could it be mostly adjusting the txv for the correct liquid to flash gas ratio

    oh and its only a single 1/2 distributor off of the txv, not multiple tubes so i used the enclosed oraface from the txv package, unless the enclosed was made for multiple tubes, there was only one in the package and the literature didnt mention needing needed a different one for different apps,only that it was adjustable for super heat to allow more or less liquid, and the supply house posidly gave me the txv for the evaporator and condensor they recomended for the replacement system(johnstone supply)

  10. #10
    Join Date
    Aug 2004
    Location
    chicago
    Posts
    123
    Originally posted by prestiege
    ill have to adjust the valve again tomorrow right now its back to the factory setting at least i think form counting the turns

    pressure on the suction side is near 50psi(because im thinking the coil will run at near 26 degrees and thus cool the box) yet actual temp of the suction line is 70-74 at compressor, temp at txv bulb is round is like 58,

    could this difference between the txv bulb and the compressor inlet be because the suction and disharge are wrapped in insulastion together, i mean they have to be welded together or something, i couldnt eve pull them apart

    im sure they are pretty old but but i blew them out with nitrogen so any oil from the old system was forced out.
    inside should be clean as a whistle.

  11. #11
    Wow!! I'm overwhelmed. This one post could suffice for the first two years of the apprenticeship training course. If you are trying to get a 35 degree box you will probably need at least a 20 degree coil based on the normal sizing for this type of aplication. 50 psi is not going to cut it at all. is the box temp still very high. What controls the condensing unit, a tstat in the box or a pressure switch on suction.

  12. #12
    Join Date
    Jul 2003
    Location
    Fort Worth, TX
    Posts
    219
    Sounds like you're undercharged. First, don't worry about the suction pressure. Get the superheat right. Think A/C, what happens when the system is low on charge...it might freeze up and probably hasn't been cooling well. Why? Because the coil inlet is colder than normal, but the rest of the coil is what is called inactive, it is not providing useful cooling since it has no liquid in that section to boil off and absorb heat, just cools a little bit. Charge by subcooling if you have no sightglass (add one like the others say. Makes charging and troubleshooting much easier)

    Once the superheat is around 10 to 12 degrees, check the temperature difference between the coil temp, by converting pressure to temp on your gauges, and the air ENTERING the evap. This temp difference should be at least 10 degrees.

    BTW, be sure to measure suction line temp for superheat before it attaches to the liquid line. The two are soldered or brazed together to promote subcooling and insure superheat to the compressor.

    Good luck.

  13. #13
    Join Date
    Oct 2003
    Location
    southern mo.
    Posts
    323
    had a similar problem a couple years back,turned out to be a partly clogged filter dryer,you might want to run new lines just to know they are clean.good luck.

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