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  1. #1
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    Problem with cold room



    We prepared a cold room by our-self. Body material sandwich-panel, size: 6'X7'X8' (LXWXH), required temperature: 5-15 Deg C. For the cooling purpose we use a 2 ton spare split type AC outdoor unit, cold room cooling coil, danfross expansion valve & filter dryer. Controlling system with temperature sensor and controller as required.

    Our problem is, at first the system is running without problem after reaching required set temperature compressor stopped as required but not starting when required (As set temperature value). Our controlling system is ok.

    We are using R22 refrigerant. Compressor is taking 7-8 amp at running condition and it is normal.

    Compressor specification as follows: Mitsubishi, Model Number TH338, hermetic
    Last edited by Bashir01219; 15-02-2012 at 09:40 AM.



  2. #2
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    Re: Problem with cold room

    Is the compressor getting power but not starting?

    Many air con compressors are not designed for starting under load as is the case with a expansion valve, so assuming the start capacitor is ok now, the addition of a start relay and start cap should help with starting the compressor when its used outside its design conditions.
    Mostly found in Oxfordshire, UK :)

  3. #3
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    Re: Problem with cold room

    fit a 5 min delay timer

  4. #4
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    Re: Problem with cold room

    yes compressor is getting power and not starting. And we have 3 min delay timer for compressor. Starting capacitor is ok. I am not clear did you say to install another capacitor?

    Quote Originally Posted by monkey spanners View Post
    Is the compressor getting power but not starting?

    Many air con compressors are not designed for starting under load as is the case with a expansion valve, so assuming the start capacitor is ok now, the addition of a start relay and start cap should help with starting the compressor when its used outside its design conditions.

  5. #5
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    Re: Problem with cold room

    monkey meant that you have to fit a potential relay with an additional start capacitor

  6. #6
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    Re: Problem with cold room

    Quote Originally Posted by tonyelian View Post
    monkey meant that you have to fit a potential relay with an additional start capacitor
    What Tony said!

    Sometimes called a hard start kit, don't know whats available in your part of the world.
    Mostly found in Oxfordshire, UK :)

  7. #7
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    Re: Problem with cold room

    Yes its available in our country, but we solve the problem in a different way.
    As we realize that when compressor stop at low temperature, the pressure trapped between compressor & expansion valve connecting copper pipe is high enough that compressor is not able to run when required.
    We come with two solution, one: a bypass line at discharge with solenoid valve that will release pressure when compressor stop, and two: replace expansion valve with a capillary tube.
    We chose the second one and its working.
    Now we are observing the unit.
    Thanks all of you to help me.
    Quote Originally Posted by monkey spanners View Post
    What Tony said!

    Sometimes called a hard start kit, don't know whats available in your part of the world.

  8. #8
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    Re: Problem with cold room

    Fit and install the high torque start kit anyway, otherwise you will flood compressor at start and go back to a TX valve and add a receiver vessel as well.
    You ask for qualified advise and totally ignore it, with your high ambients and humidity, plus using and ac compressor. If you ignore global advise, why ask in the first place. It is your arz on the line.

  9. #9
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    Re: Problem with cold room

    I apologize.
    We are still in trial & error stage. We are looking for a high torque start kit (anyway). The unit have a suction accumulator, so is it required to install a receiver? If yes then, where?

  10. #10
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    Re: Problem with cold room

    hi
    if you use a cap tube you dont need a receiver.if you fit an expansion valve you must fit a receiver after the end of condenser before the filter drier

  11. #11
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    Re: Problem with cold room

    min. time for restart is 4 minute ,
    I use a lots White Westinghouse AC unit 24000 BTU
    ( compressor +condenser unit with fan + without 4 way valve +cap tube ) to cool 35c water to 24c in small gold casting system , with new wiring system and new evaporator (coil pipe )and with 2 high pressure (one for compressor and second one for condenser fan in winter )
    Always I put 5 minutes time for restart and it works well may be I made from this system more than 50 and it work in different condition area .
    I checked to reduce the time . 3 minutes is less . minimum time is a 4 minutes .

  12. #12
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    Re: Problem with cold room

    Quote Originally Posted by mbc View Post
    min. time for restart is 4 minute ,
    I use a lots White Westinghouse AC unit 24000 BTU
    ( compressor +condenser unit with fan + without 4 way valve +cap tube ) to cool 35c water to 24c in small gold casting system , with new wiring system and new evaporator (coil pipe )and with 2 high pressure (one for compressor and second one for condenser fan in winter )
    Always I put 5 minutes time for restart and it works well may be I made from this system more than 50 and it work in different condition area .
    I checked to reduce the time . 3 minutes is less . minimum time is a 4 minutes .

    I tried to tell him but he ignored me....

  13. #13
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    Re: Problem with cold room

    Quote Originally Posted by r.bartlett View Post
    I tried to tell him but he ignored me....
    No one ignored you, Sir

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