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Thread: Condenser pressure drop circuit 1 restriction

  1. #1
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    Condenser pressure drop circuit 1 restriction

    Hello all,

    We recently picked up a new customer and replaced circuit 1 compressor for a 10 ton R22 Trane RTU heat pump system (WSC120A4). We did everything by the book. We used clean r22. We are getting a 50 psi drop between condenser and liquid line circuit 1. Ambient 79* degrees, discharge pressure 153psi, LL 101psi, suction 35psi, SH 63*, SC 3* in cooling mode, in heat mode discharge 150 psi, suction 55-65 psi swing, SC 3*, SH 45*. Condenser is tube and fin, outdoor txv with external check valve for cool mode, indoor piston. Cooling flow goes through condenser comes out of liquid line through check valve through outdoor txv distributor tubes back into condenser and out to common liquid line. Reversing valve not leaking by or any other noticeable restrictions. Circuit 2 has 15psi drop between condenser and common liquid line. We installed access ports on circuit 1 and 2 common liquid lines. The unit is about 15 years old, so the customer not interested in replacing coil. Is there any solution to flush the coil or assist with the restriction?

    Thank you in advance

  2. #2
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    Charge it correctly and recheck.
    sc low, sh high, condenser approach low
    ll reading may be due to gas pressure drop thru filter drier that should be liquid

  3. #3
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    Weighed in correct amount. No filter drier on common liquid line, only drier on system is attached to outdoor txv which is only in use during heating mode. We added 2 extra pounds to see if our pressures changed, but remained the same. Common liquid line tee's off to condenser txv.

  4. #4
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    What type of comp? Recip/Scroll? I have seen a recip that had valve reeds that shattered and the pieces got stuck part way thru the cond coil causing the problem as described by you.

  5. #5
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    If there is a 50 psi drop across that condenser verified by gauge, and no components in between the gauge ports other than condenser, I would think a restriction to be most likely where the liquid line exits the condenser. (Overall tubing area is the smallest by far)
    Might be a good idea just to pull charge and cut that connection out, don't heat it up with a torch , cut the connection out and look in there. I've had black, tar like substance in there on two separate Trane package units. One of them was R22, the other was 410A.
    I had used a torch on them and both times it showed thick black goo that hardened as it cooled.
    That, tied in with that the owner said it never worked as well as after that repair was made, made me think that the factory left a plug in the condenser that melted , but stuck there, when the unit was assembled/brazed , and that caused a restriction from day one.

    Sent from my SM-G950U using Tapatalk

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  7. #6
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    Quote Originally Posted by TechmanTerry View Post
    What type of comp? Recip/Scroll? I have seen a recip that had valve reeds that shattered and the pieces got stuck part way thru the cond coil causing the problem as described by you.
    I witnessed that with the Copeland Discus earlier models, never on a recip.

  8. #7
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    I'm a little confused.

    You keep saying "cooling flow", but you are referencing "outdoor" components, and seem to be describing refrigerant flow for heating mode.

    You are also saying "common liquid line"....do you mean both compressors are on the same refrigerant circuit?

    In cooling mode, the refrigerant should leave the compressor discharge, travel through the reversing valve into the condenser, then out of the condenser, through the outdoor metering device (or bypass), to the evap., back to the reversing valve, then to the accumulator, and finally back to the compressor.

    So where exactly are you checking your pressures to see that drop?

  9. #8
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    What was your charge amount ?

  10. #9
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    Thread Starter
    Scroll

  11. #10
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    Quote Originally Posted by 71CHOPS View Post
    I'm a little confused.

    You keep saying "cooling flow", but you are referencing "outdoor" components, and seem to be describing refrigerant flow for heating mode.

    You are also saying "common liquid line"....do you mean both compressors are on the same refrigerant circuit?

    In cooling mode, the refrigerant should leave the compressor discharge, travel through the reversing valve into the condenser, then out of the condenser, through the outdoor metering device (or bypass), to the evap., back to the reversing valve, then to the accumulator, and finally back to the compressor.

    So where exactly are you checking your pressures to see that drop?
    I’ve seen Trane use some interesting piping that it seems like the OP is describing. They run the refrigerant back through the outdoor coil, a subcooling loop. I believe the “common” liquid line they are referring to is just the 3/8 line connecting indoor and outdoor coil.


    Sent from my iPhone using Tapatalk

  12. #11
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    Quote Originally Posted by icy78 View Post
    If there is a 50 psi drop across that condenser verified by gauge, and no components in between the gauge ports other than condenser, I would think a restriction to be most likely where the liquid line exits the condenser. (Overall tubing area is the smallest by far)
    Might be a good idea just to pull charge and cut that connection out, don't heat it up with a torch , cut the connection out and look in there. I've had black, tar like substance in there on two separate Trane package units. One of them was R22, the other was 410A.
    I had used a torch on them and both times it showed thick black goo that hardened as it cooled.
    That, tied in with that the owner said it never worked as well as after that repair was made, made me think that the factory left a plug in the condenser that melted , but stuck there, when the unit was assembled/brazed , and that caused a restriction from day one.

    Sent from my SM-G950U using Tapatalk
    Correct, verified by analog gauge.

    The first liquid line comes out of condenser through check valve into outdoor txv distributor then back into condenser to get cooled again comes out of condenser tee's off to outdoor txv and indoor metering device (biflow piston).

    The access port we installed is on the main liquid line between evap and cond. We are going to install access port on the first liquid line as soon as it exits condenser.

  13. #12
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    Quote Originally Posted by Shane Bird View Post
    I’ve seen Trane use some interesting piping that it seems like the OP is describing. They run the refrigerant back through the outdoor coil, a subcooling loop. I believe the “common” liquid line they are referring to is just the 3/8 line connecting indoor and outdoor coil.


    Sent from my iPhone using Tapatalk
    Yes you are correct.

  14. #13
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    Quote Originally Posted by 71CHOPS View Post
    I'm a little confused.

    You keep saying "cooling flow", but you are referencing "outdoor" components, and seem to be describing refrigerant flow for heating mode.

    You are also saying "common liquid line"....do you mean both compressors are on the same refrigerant circuit?

    In cooling mode, the refrigerant should leave the compressor discharge, travel through the reversing valve into the condenser, then out of the condenser, through the outdoor metering device (or bypass), to the evap., back to the reversing valve, then to the accumulator, and finally back to the compressor.

    So where exactly are you checking your pressures to see that drop?
    In cooling mode, the refrigerant flow goes through reversing valve into condenser, out of condenser through check valve into distributor head of outdoor txv then back into condenser for subcooling, out of condenser, tee's off to outdoor txv inlet and indoor metering device.

    We are getting pressure drop on the common (heat,cool) liquid line which is the 3/8 line between evap and condenser.

    We are going to install access port on 1st liquid line coming out of condenser before check valve.

  15. #14
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    Quote Originally Posted by VTP99 View Post
    What was your charge amount ?
    8 pounds for circuit 1

  16. #15
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    Thank you all.

    We are going to install access port on liquid line as soon as it exits condenser before check valve.

    We will follow up with pressures.

  17. #16
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    Quote Originally Posted by Elite-Mech View Post
    8 pounds for circuit 1
    Yep that's what I'm seeing, well close enough
    Attached Images Attached Images  

  18. #17
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    Why is the discharge pressure so low for that ambient ?

  19. #18
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    Quote Originally Posted by VTP99 View Post
    Why is the discharge pressure so low for that ambient ?
    We do not know.

    I am assuming refrigerant is being stored in condenser reason being why subcool temp is low and due to low suction pressure there is not enough load to raise discharge pressure.

  20. #19
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    What's the possibly your reversing valve is bypassing some low side pressure ?

  21. #20
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    Low sub-cooling would be low charge in the condenser.

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