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  1. #1
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    Dec 2007
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    South Eastern Missouri
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    472

    Cold plate freezer in ice cream truck

    Had a job thrown into my lap last night by an old customer. I'm not a refrigeration guy other than home appliances and ice machines so I'm not sure how to charge this thing.

    I know from the compressor numbers (Copeland KANB-005E-1AA-800) that this is a R404a compressor but there is no data plate on the freezer to tell me how much refer to charge it with after I fix the cap tube leak. So other than weighing in the charge how should I charge it by gauge when the plates are warm?
    A people who would exchange liberty for apparent safety, will deserve neither and lose both.

  2. #2
    Join Date
    Jul 2000
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    Guayaquil EC
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    Since it's a cap tube system and there's no charging info, I'd charge by superheat. If the evaporator outlet is accessible, 4-6F would be a good target. If it's not, go with 20-30F at the compressor.

    In the old days, we used to charge by watching the frost on the suction line. You wanted frost coming out of the box, but just short of the compressor inlet...at least that's how Dad taught me to do it.

    For initial charging...to get started...going from a good vacuum, charge liquid to the high side until the flow slows down a bit. That should get you off the ground. Then slowly adjust the charge as the box pulls down to setpoint. It will take some time, so be patient.

  3. #3
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    Quote Originally Posted by icemeister View Post
    Since it's a cap tube system and there's no charging info, I'd charge by superheat. If the evaporator outlet is accessible, 4-6F would be a good target. If it's not, go with 20-30F at the compressor.

    In the old days, we used to charge by watching the frost on the suction line. You wanted frost coming out of the box, but just short of the compressor inlet...at least that's how Dad taught me to do it.

    For initial charging...to get started...going from a good vacuum, charge liquid to the high side until the flow slows down a bit. That should get you off the ground. Then slowly adjust the charge as the box pulls down to setpoint. It will take some time, so be patient.
    Thank you, now I have something get me started anyway. Since he lives 25 miles form me I want to get it right the first time if possible so I will spend some time with it today. I am still waiting for the supply house to get the R404a here before I can go out to the job site though.
    A people who would exchange liberty for apparent safety, will deserve neither and lose both.

  4. #4
    Join Date
    Dec 2007
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    South Eastern Missouri
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    472
    Opps, think I messed up here. It has what looks like a cap tube coming out of the LL filter dryer, that is where the leak is, but it has an TXV on it. My mistake, it was dark last night so...:/
    A people who would exchange liberty for apparent safety, will deserve neither and lose both.

  5. #5
    Join Date
    Oct 2011
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    Chicagoland Area
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    Is there a receiver? Get some dimensions. Can get a good idea that way. Who makes the condensing unit? I do a good amount of work on Thermoking units for a vending company.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

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  6. #6
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    Dec 2007
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    South Eastern Missouri
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    Quote Originally Posted by 2sac View Post
    Is there a receiver? Get some dimensions. Can get a good idea that way. Who makes the condensing unit? I do a good amount of work on Thermoking units for a vending company.
    No receiver and what looked to me like a txv in the dark last night is something else, not sure what it is. You can see it in the picture. The leak was in the cap tube coming out of the LL dryer to the right of the pic it then wraps around the suction line for some sub cooling and enters a larger line as it enters the cabinet. Pretty simple design but like I said, I'm not really a refer guy so not used to med or low temp stuff.

    The box was hot, 65, so all I could do was charge until the suction line started to get cool and some of the frost went away where the cap tube ended at the cabinet entrance. I will proly have to go back out there tomorrow for a final charge when the box is at least cold, will be better able to get readings then. I charged as much as I dared without flooding the plates but never got the suction to frost, maybe tomorrow.
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    A people who would exchange liberty for apparent safety, will deserve neither and lose both.

  7. #7
    Join Date
    Sep 2010
    Location
    Western, MO
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    871
    I think you did all you could under the circumstance. I wouldn't feel good being in that situation if I didn't go back to check and adjust once it pulled down. Even if they called and said it was working great.

    jim
    Common sense isn't very common anymore.

  8. #8
    I believe the picture is a crankcase pressure regulator. Im sure someone else with more experience can shed more light on this, but its my understanding to properly charge this system that regulator will need to be fully open.(?)

  9. #9
    Join Date
    Oct 2011
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    Chicagoland Area
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    Quote Originally Posted by nathan_a View Post
    I believe the picture is a crankcase pressure regulator. Im sure someone else with more experience can shed more light on this, but its my understanding to properly charge this system that regulator will need to be fully open.(?)
    The job of the CPR is to prevent the compressor from overamping under a high load.

    Looks like a cap tube from the pic. If you can't get a weight from the mfg, charge by SH. You may need to wait a day and recheck to tweek the charge.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  10. #10
    Join Date
    Dec 2007
    Location
    South Eastern Missouri
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    472
    Quote Originally Posted by 2sac View Post
    The job of the CPR is to prevent the compressor from overamping under a high load.

    Looks like a cap tube from the pic. If you can't get a weight from the mfg, charge by SH. You may need to wait a day and recheck to tweek the charge.
    Thanks for the info, I am planing to recheck it to morrow when it's had time to get cold.
    A people who would exchange liberty for apparent safety, will deserve neither and lose both.

  11. #11
    Join Date
    Sep 2007
    Posts
    176
    Not sure they would run that system w/ a cap tube. Looks like a TXV but if so where is the sensing bulb capillary. If not a TXV then where is it? The pic triggers more questions than it answers. Maybe more pix. Would love to trace those cap tubes a bit. Can't believe there is no receiver, or even a suction accumulator.

    You've got to get the temp down quite a bit to get to steady state and check SC/SH. The box has 4 hold-over plates that are filled with brine which freezes at -12*, and it takes a long time to pull all that mass down and freeze the brine. Low side of 10-12 psig would be about right once the plates are frozen, tho the system will go to -40; but you don't need to go that low. Hi side ball park is about 275 psig.

    Those plates are connected in series, the copper zig-zags thru them, that is your evap. Dole Refrigeration still makes the plates. Schwan's Foods trucks for example still use them. Looks like very little of the original stuff is there, they would have come with a heat exchanger and a receiver.

    Once the brine in the plates is frozen, you have a huge reserve of cold to allow the truck to travel in neighborhoods all day and not melt product in the summer. If you start with fully frozen plates at 10 AM, and go snaking thru the neighborhoods selling ice cream, you can make it to about 8 PM and still have a box temp of about zero

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