Too complicated?
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  1. #1
    Join Date
    Aug 2008
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    4

    Question Too complicated?

    No response to my first question so will ask again; maybe HVAC is just too damn complicated for anyone to know the answer.
    Will a 410a system work properly without a TXV at the coil?
    After half a dozen visits over three years, the latest service tech tells me the installers put the wrong type valve in my Carrier 410a system (38TXA / CD5A) and the system will almost always freeze up to some degree unless it has a TXV. Says he's 100 percent sure that a TXV kit to replace the piston valve near the coil will make the system work right. Says he's never seen a piston valve in a Puron system. None of the other techs ever noticed this; they claimed the problem was line-related, airflow-related or just a poor install. Carrier booklet says the 38TXA is equipped with piston valve but may be upgraded with a 410a TXV. System was installed by a company with a good reputation; service contract is with a company with an excellent reputation. But EVERY service tech has a different explanation; do any of these guys know what the heck they're talking about?

  2. #2
    Join Date
    Apr 2008
    Location
    Alberta Canada
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    2,246
    I think you mean, fixed orfice piston metering device. They will work as long as the right size is used, usually marked on condensor which #. A TXV will make the system alittle more efficient.

  3. #3
    Join Date
    Aug 2008
    Posts
    4
    I'm sure that's what he meant by piston valve. The coil had frozen (again) and the tech checked several things. Said the system was actually overcharged with 410a, that there appeared to be no leaks, then said "they installed the wrong valve". Said Puron's higher pressure requires a more sensitive valve (the TXV) and without it the system would never work right. Sounded like BS to me but what do I know? I didn't attend MIT/Princeton, which seems like what is required understand these systems. Right now I'm trying to slowly bring the house down to 80 degrees, have opened up all the returns. Thanks for the reply.

  4. #4
    Join Date
    Jun 2007
    Location
    Round Rock
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    3,511
    You have to look on the condenser rating plate. It will tell you whether a TXV is required or not. It will give a piston size to use or just say TXV on it. The newer ones usually require a TXV, but the older ones didn't. I've installed many 410 system with a piston with no problems. There could be a number of other problems as well.

  5. #5
    Join Date
    Apr 2008
    Location
    Alberta Canada
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    Tell him he is full of something and its not R410A. I have Installed for years r410a and no problems for me. Tell him to get someone compitent cause he can't even make a face like a A/C tech.

  6. #6
    Join Date
    Jun 2005
    Location
    Las Vegas NV
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    1,152
    Quote Originally Posted by witsend View Post
    have opened up all the returns.


    Can you explain this statement.

    Have the returns been blocked or shut off? Are the supply vents all open?

  7. #7
    Join Date
    Feb 2008
    Location
    Western NC
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    2,504
    Quote Originally Posted by powell View Post


    Can you explain this statement.

    Have the returns been blocked or shut off? Are the supply vents all open?
    I caught that too.

    Seems like the problem is a combo of operator error and pathetic technicians not doing a full diagnosis.
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  8. #8
    Join Date
    Jul 2002
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    NY
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    Could be the wrong piston in the TXV. In chillrooms that I have installed they have a TXV with different pistons in them depending on what gas you are putting in. This could be the problem.
    Not what it use to be

  9. #9
    I don't see why the piston would be a problem. I am a txv fan myself. The txv just allows the system to operate more efficiently of a wider temp range. Sounds like an airflow problem or a starved coil either of which could be caused by a multitude of problems.

  10. #10
    Join Date
    Jul 2002
    Location
    NY
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    Quote Originally Posted by blue83camaro View Post
    I don't see why the piston would be a problem. I am a txv fan myself. The txv just allows the system to operate more efficiently of a wider temp range. Sounds like an airflow problem or a starved coil either of which could be caused by a multitude of problems.

    This post might get way off base but TXV's with the wrong piston in them will not work. That's why they have different pistons with them. Not saying that this is the problem but you never know.
    Not what it use to be

  11. #11
    Quote Originally Posted by itsamine View Post
    This post might get way off base but TXV's with the wrong piston in them will not work. That's why they have different pistons with them. Not saying that this is the problem but you never know.
    What do you mean by "piston in a txv"?

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,630
    Only Rheem/Ruud uses a balancing piston in heat pumps/A.Cs.

    Your thinking of a medium or low temp refrigeration system.
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    How many times must one fix something before it is fixed?

  13. #13
    Join Date
    May 2006
    Location
    Philadelphia, PA
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    1,373
    Sounds like someone tried to compensate for low air flow by overcharging the system. I suggest you find a competent tech in your area evaluate this system before spending much more money on what sound like guesses.
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