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Thread: True, GDM72F

  1. #1
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    True, GDM72F

    Hello All,

    One again with a with some problems.

    I was on a call for True, GDM72F freezer. To begin with this, It had a leak in suction line because of vibration and liquid line hitting the suction line.
    I braze the suction line and replaced the filter drier. Pressurized the system with nitrogen and found suction service valve was leaking . Replaced the valve. Again pressurized, no leak. Then vacuum it and weigh in 41oz of 404A.
    Box temperature was 78f, Room temperature 74f, High pressure was at 230 psi and low pressure was 13 psi. Freezer ran for around 10 minutes on these pressures but still the evaporator fans did not came on. then suddenly low pressure started dropping. It went to 5psi.
    I let it run for next 10 to 15 minutes. but evaporator motors did not came on.
    Super heat 6 inches away from compressor was 105f and sub cooling was 9f. Also i would like to mention that it has a crank case pressure regulator on it and the low side pressure was same on both sides.
    Shut it off. Recover the refrigerant. open the capillaries from both ends. Clean the capillaries with nitrogen. Braze it back and with new filter drier, vacuum it and charged it.
    Same results.

    Please advise.

    Thank you.

  2. #2
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    Let it run, could take up to 20 minutes or more for the EVAP fans to come on. What kinda micron you get on vac?

  3. #3
    Join Date
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    Check those door switches. Might have a bad one or a loose connection at one.

  4. #4
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    It can take a while for the fans to come on. What type of control is on the unit? You can sometimes see the p2 evaporator sensor on the controller to see if it is cooling.

    Those pressures do seem low for r404a, but need all fans running to be sure.

  5. #5
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    Quote Originally Posted by sam's View Post
    open the capillaries from both ends. Clean the capillaries with nitrogen.
    It is not possible to "clean" the lining of sludgy deposits that develop on the inside of a capillary tube with nitrogen. Replace the captube.

    Edit: If this is a new unit, it is probably a moisture issue or undercharge vs clogged captube. A lot of the new units have massive condensers and will run very low suction pressures. But having a CPR valve and suction service valve I'm quite confident this is an old True with a semihermetic compressor.

    Sent from my SAMSUNG-SM-G890A using Tapatalk

  6. #6
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    True has a somewhat involved procedure for cap tube changes. But, they DO have one, which suggests to me that this is a known issue.

    I was asked to do a compressor and start components box on one of these a few weeks ago, and got by without doing the cap tube. I had no service valves of any kind, though. Is this unit using a small Copeland semi hermetic?

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  7. #7
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    What is the temp of the evaporator?

  8. #8
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    Thread Starter
    Good afternoon everyone,

    Thank you all for taking time and advising me.
    Yes, its old True with semi hermetic.
    I called True and they advised me to change compressor oil filter drier and change the captubes. The recommended size is 0.46 and 7 feet long each.
    I could not find the True parts near me. So i used Supco# 3. I matched it according to the chart came with the new captubes for 1 1/2 hp compressor. Changed the compressor oil and replaced the filter drier. Vacuum the system and charged the 41oz of 404a refrigerant. Yes i did checked defrost switch and door switches. All of them were working fine.
    After charging, Unit started working good. Low side at 14psi and high was at 245psi. Starting box temp was at 72f and little over in 10 minutes evaporator fans started working.
    Gentlemen, Thank you very much for all of the input and support.

  9. Likes joejax liked this post
  10. #9
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    Quote Originally Posted by sam's View Post
    Good afternoon everyone,

    Thank you all for taking time and advising me.
    Yes, its old True with semi hermetic.
    I called True and they advised me to change compressor oil filter drier and change the captubes. The recommended size is 0.46 and 7 feet long each.
    I could not find the True parts near me. So i used Supco# 3. I matched it according to the chart came with the new captubes for 1 1/2 hp compressor. Changed the compressor oil and replaced the filter drier. Vacuum the system and charged the 41oz of 404a refrigerant. Yes i did checked defrost switch and door switches. All of them were working fine.
    After charging, Unit started working good. Low side at 14psi and high was at 245psi. Starting box temp was at 72f and little over in 10 minutes evaporator fans started working.
    Gentlemen, Thank you very much for all of the input and support.
    The equivalent length of the OEM size to a BC3 you posted would be just over 12 feet
    Not sure what the chart told you to put in.

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