Tech says possible contamination?
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  1. #1
    Join Date
    Feb 2005
    Posts
    27
    I have a 410a system installed 6 months ago and called for a PM since it is getting warm in Southern California. Furnace checked out just fine, filters are clean. Tech was checking charge on my Lennox HSX 19, stated on paper "by approach method temp split is 18degrees" but tech told me that pressure split was not right. He said it might be from contamination or a kink in the line. So he recommended to recover, and pump down unit and re-charge with new refrigerant and check pressures again. Does this sound like a reasonable plan? Should filter-drier also be replaced? I would appreciate your guidance.

  2. #2
    Senior Tech Guest
    Would need a lot more info than given...and yes, if the system is opened it MUST have a new drier installed EVERY time.

  3. #3
    Join Date
    Feb 2003
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    258
    Depends on who is paying.

  4. #4
    Join Date
    Sep 2004
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    172
    yep sounds just right, start with the basics when you don't know who or what was done at a install, (yes absolutely change the filter drier) especially with a 410a system which he probably knows very little about. Is this warranty work from the installer? I am betting that this guy will figure out your system and will have it working perfectly although at that point someone may have a huge bill to pay hopefully not you. I would get that clarified before he starts his learning/training program on the unit. I hope the poor guy has not fallen into the old well I checked that syndrome, oh you guys know that mode, the tester is set to the wrong setting/the sun gets in your eyes and you read the wrong pressure temp, or the old I really did not have time to go in and check to see if the HO had maybe completely closed off all the floor vents but one and had one of the dirtiest return filters ever seen, lets just geturdun bohy.

  5. #5
    Join Date
    Sep 2002
    Posts
    4,970
    If that is the installing company that is servicing your unit , I would have them explain what went wrog. If is not the installing company , I would call them and have them explain it. If no one else has messed with it but the original installing copany I would think some sort of warranty should cover it . Now as far as filter dryers and such.........better look at the fine print.

  6. #6
    Join Date
    Feb 2005
    Posts
    27
    It is the installing company, and yes it is being done under warranty. They are not planning on opening the system, but just replacing the refrigerant in case it is contamination causing the problem with pressures. If the system will be kept closed, should the filter-drier need replacement. I watched as they did the install, from what I read here they did not purge the system with Nitrogen prior to pulling vac. Could this be source of contamination?

  7. #7
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Why would they recover and recharge if they suspect a kinked line? Doesn't make sense to me, pull the charge, weigh in new charge, still kinked line same problem. If they can't find the "kink" what are they going to do next change the lineset? Something sounds fishy here.

  8. #8
    Join Date
    Feb 2005
    Posts
    27
    Black Adder the line set is definately not kinked he and I checked that, we did not opent the evap coil. The pressure difference the tech was speaking off was "little" he does not know what the contamination might be, but wants to change refrigerant to see if this resolves it. Does this seem right? What about needing to change filter drier in a system that will be kept closed.

  9. #9
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,279
    Here we are again, discussing what might ail a refrigeration circuit with insufficient data.

    While Lennox may favor the approach method for checking charge on their systems, I'm not satisfied to just go with that and call it a day. I would like to see the superheat and subcooling readings, the deltaT over the evap, compressor amp draw, outdoor ambient temp, etc. As a homeowner, discussion of these readings may be puzzling, but your technician should be familiar with them.

    If the system is only going to be recovered, evacuated, and recharged with virgin refrigerant, I see no need to cut open the liquid line and sweat a drier in, unless the technician suspects considerable moisture in the system. There are ways to check for moisture in the system while the existing charge is still there, so if he were to do this test and it indicated elevated moisture levels, installing a new liquid line drier is a no-brainer.

    I have yet to work with a 410A system but my understanding is that the superheat/subcooling parameters are similar to R22 systems.

    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  10. #10
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Ya Shophound I think the readings and methods of obtaining superheat and subcool are the same, just the numbers are different. Just have to use a 410a chart.

  11. #11
    Join Date
    Sep 2004
    Posts
    3,157
    we did not opent the evap coil. The pressure difference the tech was speaking off was "little" he does not know what the contamination might be, but wants to change refrigerant to see if this resolves it. Does this seem right?

    If he suspects contamination Why would you change the refrigerant without opening the system and removing the contamination/dryer

  12. #12
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,279
    If he suspects contamination Why would you change the refrigerant without opening the system and removing the contamination/dryer
    It's all in how "contamination" is being defined by this technician. If he's referring to noncondensables, that's what the recovery, evacuation, and recharge would address. If he's talking moisture and questionable oil purity in addition to noncondensables, then yes sir, do all of the above and install the liquid line drier. And flow nitrogen while brazing that puppy in.

    It's hard enough seeing installers flow nitrogen while brazing. Same for many techs. If this tech were to pull down the system, cut open the liquid line and sweat in a drier, all without flowing nitrogen, he's just introduced more contaminants into the system via not back-shielding his brazing with nitro. He could proceed from that point with his evac and recharge of virgin refer, but now he's got trash circulating around that sloughs off the inside of the copper pipe that no evac can pick up.

    But it comes back to whether this technician understands superheat/subcooling enough to know he has noncondensables in the system. The more data one can gather on a system (and understand what that data means), the better.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  13. #13
    Join Date
    Feb 2005
    Posts
    27
    Tech will be here tomorrow to pull down and replace system with virgin 410a. Do any of you have some kind of flowsheet charting that I can use to obtain pertinent data that I can post here afterwards? (Such as a piece of paper with checklist to write down pressures and other data) I would like to post it here for a critique, and proof that my system was indeed fixed.

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