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  1. #1
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    404a cool room operating pressures


    Hey guys.
    Just wondering what kind of suction and head pressures you could expect in a 404a cold room setup.
    System originally ran on R22, seized compressor.
    Swapped out the compressor, new one is a 404a. (I did not order the new parts)

    Charged it by the weight on an info tab on the system, got called back for evaporator icing up.

    Got back, giving all signs of short of gas. Then the thought struck me. Don't have a leak, but the new gas charge would be higher than the old one as 404a is higher pressure than 22.
    Whilst charging, unit started tripping on HP.
    Figured it was because of the old HP sensor not set high enough for new gas.

    Which leads to my question: what kind of head pressure would a 2-4'C cool room run at (inside a pizza hut so 22-30 ambient), and what kind of HP setting would you set.
    Also, what suction pressure would you look for.

    Capillary, fan-forced evaporator.



  2. #2
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    Re: 404a cool room operating pressures

    Has the capillary been changed for one suitable for R404A?
    Is this a little packaged system or a field built up system?
    Hot gas or electric defrost?

    I'm wondering if its got a blocked up cap tube from running R404A and mineral oil as was in old comp, or it may just have blocked up for fun.

    Just because R404A runs at higher pressures than R22 doesn't mean there needs to be more of it in the system.

    Jon

  3. #3
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    Re: 404a cool room operating pressures

    i would leave on reclaimed 22 or a drop in refrigertant ... the comp being on ester will work fine on provision it was designed for a cap system if you did convert to r404a on start up you would run high pressure due to room temp useually low up to 45 to 55 psi and high at 250 to 290 with that room ambient

  4. #4
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    Re: 404a cool room operating pressures

    If it was a 22 system then the Cap, if it is a capillary system, will be sized for R22, not R404a.

    That's always assuming that it's not a TX system, in which case the TX valve will have to be changed for a R404a valve.

    Your best bet would have been to drain the poe oil and replace it with the same volume of mineral oil and, as said above, recharge it with R22.

    The poe oil will act like a detergent and any carbon and crap in the system will get washed out and, as aalso mentioned above, block your capillary.

    For future reference..

  5. #5
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    nevgee is offline Veteran Poster I am starting to push the Mods: of RE
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    Re: 404a cool room operating pressures

    Quote Originally Posted by Slatts View Post
    Your best bet would have been to drain the poe oil and replace it with the same volume of mineral oil and, as said above, recharge it with R22.

    The poe oil will act like a detergent and any carbon and crap in the system will get washed out and, as aalso mentioned above, block your capillary.

    For future reference..
    R22 is compatible with both mineral and POe.
    As you rightly say POe is a good cleaning agent, therefore, always fit a new strainer / filter drier.
    Last edited by nevgee; 27-02-2011 at 11:37 AM. Reason: addition of txt
    Reality is an elusion created by alcohol deficiency. Quaff and enjoy. [Yorkshire, UK]

  6. #6
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    Re: 404a cool room operating pressures

    As the old compressor was on 22, I'll give you long odds it was running mineral oil.

    Going to poe is a recipe for disaster, even with a new drier, which should have been changed with the compressor anyway.

    It happens that just today I had a system that some rough b4stard had changed the compressor in and hadn't changed the drier. A 2 door medium temp display case on 134a.

    The drier was restricted.

    Also the condenser fan was fitted backwards and the condenser, though it looked clear, was blocked solid when I blew it out.

    When I say it was backwards, it was fitted to a double shafted 50d503 motor with the blade right for the rotation of the shaft used, but blowing into the condenser instead of sucking through it.

    The idea is, for anyone who isn't aware of it, the fan blows air over the shell of the compressor to help cool it.

    Works great if the condenser isn't chockers.

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