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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
    4,330
    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 2003
    Location
    Virginia
    Posts
    376
    what was the outdoor temp?? It could be low on charge...

  5. #5
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,330
    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.

  6. #6
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,330
    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.

  7. #7
    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.

  8. #8
    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....

  9. #9
    Join Date
    Mar 2010
    Posts
    8
    ascj. I unscrewed the bottom of the valve where the spring is located and inside where the refrigerant comes in is this Orifice. The best way I can explain it is a small cylinder with 2 small ports at the bottom where the refrigerant comes in and an open end that enters the main valve where the spring is located???

  10. #10
    Join Date
    Mar 2010
    Posts
    8
    Proefco. I had just ghanged out the dryer today after seeing my pressure's and the first thing I checked was for some kind of freezing. I could not find anything even at the txv. My line temp pretty much through the system was about 71-72.

  11. #11
    Join Date
    Jun 2003
    Location
    Virginia
    Posts
    376
    What kind of valve is this? Is it a TXV? (with power element?) What brand? WHat size? Is this a new start-up or an existing system that was working at one time?

  12. #12
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,055
    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.

  13. #13
    Join Date
    Mar 2010
    Posts
    8
    Tis is a new start up! The valves were sent out with the equipment.... No power element, and I'm not sure on the brand. I'm really questioning the size on them, there both 4ton valves on this dual coil fed by a 7.5ton condenser.

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