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  1. #1
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    Blast freezer temperature problem. Please help!!!



    I have a blast freezer with Bitzer S6F-30.2Y compressor. It normally goes down to -35c with 1.2 ton of fish in 8 hours. After service by an unqualified technician, it now takes 14 hours to reach -14c.
    Parameters are:
    18.5Amp
    Discharge=224psi
    Suction=8psi
    Intermediate Pressure=89psi
    Superheat bulb temp=34.7c
    Oil pressure=94psi
    I also have a little ice on the suction cup at the entrance to the cylinder, but not on the cylinder head.

    I need help getting the system back to normal. Do I need to adjust the superheat or is it something else?
    Any help will be appreciated. Thanks.



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    Re: Blast freezer temperature problem. Please help!!!

    Hi Volta
    you seem to know more than the average owner
    Not a fridge guy in disguise

    If your bulb temperature you refer to is the bulb for the evaporator your plant has 60k super heat, should be say 20k at the compressor inlet, depending on the suction pipe length.

    Why not get the guy who installed it back to put it right, or have you not paid him


    Evaporator is being starved of refrigerant, short of gas, blockage somewhere or incorrectly set expansion valve.

    Kind Regards. Andy.

  3. #3
    volta's Avatar
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    Re: Blast freezer temperature problem. Please help!!!

    Thanks Andy,
    The bulb I was referring to is the superheat bulb.
    We just reloaded the system with 124kg of R507, which is the correct amount for this system.
    I already changed the evaporator TXV with a new one with the same orifice.

    I still have the same problem. Any ideas?

    I can't get a real qualified tech since my equipment is in Africa.

  4. #4
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    Re: Blast freezer temperature problem. Please help!!!

    Quote Originally Posted by volta

    I can't get a real qualified tech since my equipment is in Africa.
    Oh my god, oh my god, Marc !! Marc ,Maaaarrrrrccc!!!!! oh my god ,i can't believe you just said that,oh my god....MAAAAAAAARRRRRRRRRCCCCCCCC!!!!

    cheers

    richard

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    Re: Blast freezer temperature problem. Please help!!!

    Don't panic Rich, it'll be OK.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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    Re: Blast freezer temperature problem. Please help!!!

    Quote Originally Posted by volta
    I have a blast freezer with Bitzer S6F-30.2Y compressor. It normally goes down to -35c with 1.2 ton of fish in 8 hours. After service by an unqualified technician, it now takes 14 hours to reach -14c.
    Parameters are:
    18.5Amp
    Discharge=224psi
    Suction=8psi
    Intermediate Pressure=89psi
    Superheat bulb temp=34.7c
    Oil pressure=94psi
    I also have a little ice on the suction cup at the entrance to the cylinder, but not on the cylinder head.

    I need help getting the system back to normal. Do I need to adjust the superheat or is it something else?
    Any help will be appreciated. Thanks.
    dear

    to adjust tev ,,you must check the p-t chart of gas 507
    you can find this chart at:
    www.refrigerants.com/pics/ptchart.pdf

    if you need a blast temp. -35 , the evaporator temp. will be -38 , and with 5 dgree superheat it will match -33
    this temp. match pressur 10 psi
    so you must increase the orifice of tev by rotate it clock wise untill you get 10 psi suction pressure

    an other reason you check is:
    may be the evaporator coil may be dirty,,alot of impurities stucking on its surface,,so it must be cleaned away ,
    thats all i have to tell you
    good luck
    afeef

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    Re: Blast freezer temperature problem. Please help!!!

    I can't get a real qualified tech since my equipment is in Africa
    is that because they are all in england moaning about the ineptitude of the population?


    and 18.5 amp ?? what is that? if its the comp. running current the it sounds very low for the plant. suspect poor duty due to some kind of restriction if you are sure the charge is correct.
    Last edited by slingblade; 27-02-2006 at 11:08 AM.
    Takes a licking, keeps on ticking.

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    Re: Blast freezer temperature problem. Please help!!!

    Quote Originally Posted by volta
    I already changed the evaporator TXV with a new one with the same orifice.

    I still have the same problem. Any ideas?

    .
    Volta we will assume you are not Marc, if you are, I will do something un speakable to you, involving your knee caps, happens often over here.


    Did you set the TXV superheat, open the valve adjust screw out until the superheat lowers to 10k at evaporator outlet, you may then proceed to play with it until you get a 4.5k superheat, but I wouldn't bother.

    Fit a pressure gauge and a thermometer probe at the evaporator outlet. Read off the saturation pressure and convert to degrees c for the refrigerant used. Then adjust the valve until the probe reads within 10K of the pressure reading in Deg C.

    Then retire to the pub and tell your mates about it---------- or not as the case may be
    Kind Regards, Andy

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    Re: Blast freezer temperature problem. Please help!!!

    Quote Originally Posted by volta
    I have a blast freezer with Bitzer S6F-30.2Y compressor. It normally goes down to -35c with 1.2 ton of fish in 8 hours. After service by an unqualified technician, it now takes 14 hours to reach -14c.
    Parameters are:
    18.5Amp
    Discharge=224psi
    Suction=8psi
    Intermediate Pressure=89psi
    Superheat bulb temp=34.7c
    Oil pressure=94psi
    I also have a little ice on the suction cup at the entrance to the cylinder, but not on the cylinder head.

    I need help getting the system back to normal. Do I need to adjust the superheat or is it something else?
    Any help will be appreciated. Thanks.
    Intermediate pressure high

    and thus the oil pressure

    Bulb temp is the desuperheating bulb for the interstage, the valve has been opened up too much

    Kind Regards. Andy

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    Re: Blast freezer temperature problem. Please help!!!

    Hi

    Discharge low

    amps low

    what about the head joint, two stage bitzers would blow the odd one.

    Please fit new head joint and set desuperheat TEV

  11. #11
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    Re: Blast freezer temperature problem. Please help!!!

    am in africa and you can reach me on
    griffine.ongaro@yahoo.com
    ive installed more than five blast freezer around red sea and they are ok,just book aflight ill sort it out for you
    thanks

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    Re: Blast freezer temperature problem. Please help!!!

    Quote Originally Posted by otieno View Post
    am in africa and you can reach me on
    griffine.ongaro@yahoo.com
    ive installed more than five blast freezer around red sea and they are ok,just book aflight ill sort it out for you
    thanks
    But four years too late.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

  13. #13
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    Re: Blast freezer temperature problem. Please help!!!

    Quote Originally Posted by Brian_UK View Post
    But four years too late.
    Ha~~~, so funny
    But, Maybe Volta still need any help in Africa

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    Re: Blast freezer temperature problem. Please help!!!

    Hi there,

    I assume your TEV is MOP type.

    The head of TEV must be few degrees warmer than the bulb, if not the valve will close.
    What I do in this applications is this : use wire type heaters, like the one used in drain pipes, connect this heater on top of the TEV and insulate it. the rest must be in the air, because every one meter of this heaters must be connected to electricity. Energize this heater when compressor is on.
    The other issue you have to consider is the amount of sub-cooling. If you have sub-cooler, which you must, then you will get around 40°C sub-cooling. Select correct size of TEV orifice according to that sub-cooling. If not then your suction will be higher than it should be.

    Cheers
    Even Einstein Asked Questions

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