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  1. #1
    Join Date
    Mar 2010
    Posts
    8

    Confused Expansion valve issues???

    I am having issues with a Lennox 410a 7.5ton heatpump system. The system has a dual evap coil ran off a single ciruit compressor. My running pressure are way off with my low side at 60 and my high side at 310. I have checked the lineset for any restrictions and could not find any, I have also checked th expansion valve itself to make sure the orifice was clean. I am not a 100% that my valves are sized properly, there are 2 4ton expansion valves on this coil. Is this correct for a 7.5ton condenser and can a singal circuit compressor handle this dual coil??

  2. #2
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,340
    Quote Originally Posted by Delta31 View Post
    I am having issues with a Lennox 410a 7.5ton heatpump system. The system has a dual evap coil ran off a single ciruit compressor. My running pressure are way off with my low side at 60 and my high side at 310. I have checked the lineset for any restrictions and could not find any, I have also checked th expansion valve itself to make sure the orifice was clean. I am not a 100% that my valves are sized properly, there are 2 4ton expansion valves on this coil. Is this correct for a 7.5ton condenser and can a singal circuit compressor handle this dual coil??
    Can a single compressor handle duel circuit coil?.....sure, it's common practice.

    The orifices in the TXV's were clean......please explain that.

    Other quesions.....what cfm you moving? What SH and SC you at? You have some models numbers to share?

  3. #3
    Join Date
    Mar 2010
    Posts
    8
    I opened up my valves thinking there was a screen but found a fixed orifice instead, it was clean of any obstructions. Not sure on the cfm and have not taken any sh or sc readings yet because I am thrown by my pressure's. It seems as though I have a retriction somewhere.

  4. #4
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,340
    Quote Originally Posted by Delta31 View Post
    I opened up my valves thinking there was a screen but found a fixed orifice instead, it was clean of any obstructions. Not sure on the cfm and have not taken any sh or sc readings yet because I am thrown by my pressure's. It seems as though I have a retriction somewhere.
    Could it be you have fixed orifices and TXVs installed? I have seen it.

  5. #5
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,340
    Quote Originally Posted by Delta31 View Post
    I opened up my valves thinking there was a screen but found a fixed orifice instead, it was clean of any obstructions. Not sure on the cfm and have not taken any sh or sc readings yet because I am thrown by my pressure's. It seems as though I have a retriction somewhere.
    Could it be you have fixed orifices and TXVs installed? I have seen it. But not on Lennox, since the have the TXV's with the stem that prevents them being installed with the orifice still in place.

    Please explain finding a fixed orifice in a TXV.

  6. #6
    Join Date
    May 2008
    Location
    Myrtle Creek. Oregon
    Posts
    182
    is the unit fully charged? got to be fully charged before you can check SH properly.

  7. #7
    Join Date
    Sep 2004
    Location
    Oklahoma
    Posts
    83
    Is the line set the right size for the dual evaporators?

    Lane

  8. #8
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,060
    Quote Originally Posted by Delta31 View Post
    I opened up my valves thinking there was a screen but found a fixed orifice instead, it was clean of any obstructions. Not sure on the cfm and have not taken any sh or sc readings yet because I am thrown by my pressure's. It seems as though I have a retriction somewhere.
    stop guessing and take your subcooling and superheat readings.

    We need this basic info to actually help you.

  9. #9
    Join Date
    Mar 2010
    Posts
    8
    Quote Originally Posted by y7turbo View Post
    stop guessing and take your subcooling and superheat readings.

    We need this basic info to actually help you.
    Haven't taken them yet because if I add refrigerant my head just comes up and suction stays at 60

  10. #10
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,060
    Quote Originally Posted by Delta31 View Post
    Haven't taken them yet because if I add refrigerant my head just comes up and suction stays at 60

    dont matter what your pressures do when you add gas, you NEED to take sh and sc readings to find out what the refrigerant is actually doing inside the system.

    Are all your condenser fans on while your checking pressures?

  11. #11
    Join Date
    Jun 2003
    Location
    Virginia
    Posts
    376
    what was the outdoor temp?? It could be low on charge...

  12. #12
    Join Date
    Mar 2010
    Posts
    8
    ascj. No the orifice is inside the actual valve. Not sure if that is exactly what it is but it looks like one.
    Prorefco. Out door temp was in the low 70's and the charge is not correct I know but when I and refrigerant it just brings up my head pressure.

  13. #13
    Join Date
    Jun 2003
    Location
    Virginia
    Posts
    376
    Sounds like a restriction alright... Your possibilities are liquid drier, liquid line, metering device (TXV, accurator etc), liquid line service valve, metering device for heating/check valve. What's the temp of the liquid line at the condenser and at the air handler? With a 60 psi suction, you shoud be seeing some frost somewhere....

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