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  1. #27
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    Aug 2003
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    Fort Worth, TX
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    11,327
    Pressure testing with a nitrogen/refrigerant mix can at times find leaks that a vacuum test can't. Also, with the vacuum test, the tech won't know WHERE the leak is, only that he's not holding a vacuum. So if he detects a leak with a vacuum, what does he then have to do? Gas up the system and go hunting. Might as well do that first, find all leaks possible, and THEN pull a vacuum. Always better to do things in the right order vs. doubling back and eating up time and money.

    If a system is tight, a tech looks for the following reality when pulling a vacuum:

    System should hold at 500 microns or lower. If microns rise, level off, and hold, system has moisture in it and requires more evacuation. If system micron level rises to atmospheric, there's a leak.

    Freeze stat is not the answer. Allowing a system to run low on refrigerant, even if it still appears to cool the house, puts the compressor under stress. If the compressor can't be cooled sufficiently by suction gas, and oil return to the compressor becomes spotty, compressor life will be short and it will die an ugly death.
    • 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.

  2. #28
    Join Date
    Jul 2011
    Location
    Delaware
    Posts
    29
    Thanks for the detailed explanation Shophound. I now have enough background knowledge to ask the supervisor what was done.

    And collectively, HVAC-Talk has got me off the freeze-stat theme .... doh!

    Kevin

  3. #29
    Join Date
    Oct 2006
    Location
    The Beach
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    702
    Good for you. Installing a freeze stat will not solve the problem. Just get the system fixed and your mother will be cool.
    Blue Fox

  4. #30
    Join Date
    Jul 2011
    Location
    Delaware
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    29
    Vaccum Meter

    I talked to the tech super yesterday. I asked about the final vacuum test, and he said they pull a vacuum for about 30 minutes, followed by a 10 min hold ... if no change it's leak free. I then mentioned that microns of HG are a very small unit of measure. He started avoiding my statement, then for whatever reason, he offered up that they don't have micron meters, and they use the "meters from when Freon was used".

    Any idea what unit those meters read out? inches HG?

    As long as it is stable for 10 minutes, is that enough to verify no leak, using the old meters?

    Thanks a bunch guys!

    Kevin

  5. #31
    Join Date
    Jun 2006
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    Richmond, VA
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    2,884
    Quote Originally Posted by KevimK2 View Post
    Vaccum Meter

    I talked to the tech super yesterday. I asked about the final vacuum test, and he said they pull a vacuum for about 30 minutes, followed by a 10 min hold ... if no change it's leak free. I then mentioned that microns of HG are a very small unit of measure. He started avoiding my statement, then for whatever reason, he offered up that they don't have micron meters, and they use the "meters from when Freon was used".

    Any idea what unit those meters read out? inches HG?

    As long as it is stable for 10 minutes, is that enough to verify no leak, using the old meters?

    Thanks a bunch guys!

    Kevin
    no, sounds like they just use their compound guages- which won't tell you a thing.

    sometimes it takes longer than 30 min to get less than 500 microns.....
    Give a man a fish, he will eat for a day. Teach a man to fish, he will eat for a lifetime.

    Give a man a capacitor, doesn't know what to do. Teach a man to install it, now he knows everything.

  6. #32
    Join Date
    Jul 2011
    Location
    Delaware
    Posts
    29
    Guys, I'm in the process of finding a new contractor, for servicing my Mom's 3T AC system in Florida.

    And I appreciate all the help so far, but they have pulled a new one on me/Mom.

    She lost cooling 2 times in 3 weeks last month:

    She lost cooling on the 10th, restored on the 12th, and lost cooling again on the 15th, restored on the 17th.

    Last Sunday, Mom had to run the system all afternoon, non-stop, to maintain 80 degrees on a 88 degree day. The delta between the inlet and outlet flow was only 10 degF, vs the usual 16 degF + delta that quickly cools the house.

    Now the wierd stuff:

    On this past Monday, a bright new tech, old Rick, came out to find the problem. He said the dryers that were installed a few weeks ago had a high pressure drop across them. He thought this was due to too much heat during the solder installation. I asked him to check for Ice on the evaporator, and he said he was too old to go up the rickity drop-down stairs.

    He wrote down on the call sheet that new dryers were needed, as he discussed with me on the phone. And there was no mention of evaporator trouble on the call sheet.

    I call Mom on Tuesday, when the new dryers were going in. Another tech answers the phone and says he is installing a new evaporator. He has already done the dryers.

    I call the manager "SAM" Saten. I asked why a new evaporator was being installed, he coul not sat, but nhe did say all or nothing, so I had to say "all" to get my Mom's AC working again, but I had a bad feeling about changing out a major organ of the cooling system. I was right ... they coul not get the old evap down the fold down steps in the garage, so they were afraid to bring the new evap upstairs. They gave up and left my Mom with still no AC !!!!!

    Question

    Is it possible that the manager just inflated the warrenty work on this job, by just arbitrarily adding that a new evap coil was needed, that was only 8 months old, to fatten his pocket ???

    I appreciate your professional opinions about this problem where the tech said it was not needed, but the manager added it on anyways.

    Thanks a bunch,

    Kevin

  7. #33
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    Feb 2009
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    Tallahassee, FL
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    6,040
    We don't make money on warranty jobs. And the older guy wouldn't even look at the evap so how could he say one way or another?

  8. #34
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    Jul 2011
    Location
    Delaware
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    The system was not loosing 410A, and the evap was only 8 months old. He felt the dryers were the only problem, based on the pressure drop across them.

    Is it possible that on issue begot the other? Like the bad dryers some how messed up the evaporator? It does not work the other way, as he determined how the excessive heat (lack of using a heat sink, like wet cloth) damaged the dryers when they were installed about 3 weeks ago.

  9. #35
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    Jul 2011
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    Delaware
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    Quote Originally Posted by SBKold View Post
    We don't make money on warranty jobs ...
    If the work load is light for a couple of days, I though major warranty work would be welcomed.

  10. #36
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    Aug 2003
    Location
    Fort Worth, TX
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    Quote Originally Posted by KevimK2 View Post
    If the work load is light for a couple of days, I though major warranty work would be welcomed.
    That's not really the issue. What is the issue is that nobody so far appears to have done a thorough investigation...although measuring a pressure drop across a drier was a good move. However, if a drier plugs up, that's a sign someone working on the system in the past may not have used proper procedures regarding brazing and/or evacuation (vacuuming).

    But now you're saying that this crew removed the old evaporator BEFORE they realized they couldn't get the replacement up the attic access stairs? Or did they realize that fact prior to removing the old evaporator?

    There's no reason to change an entire evaporator coil if it's not leaking. If there's a restriction it will likely be in the metering device just prior to the evaporator, since it is the smallest portion of the entire refrigerant loop other than the driers, which are actually filters with desiccant included.

    If by some miracle the parade of techs cycling through your mother's system get the refrigeration portion of her system working perfectly, and the evaporator STILL freezes up, then that's an airflow problem, period. Getting that resolved will mean finding somebody who understands duct design and layout, who is a person as rare as hen's teeth, it seems.
    • 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.

  11. #37
    Join Date
    Jul 2011
    Location
    Delaware
    Posts
    29
    Quote Originally Posted by Shophound View Post
    That's not really the issue. What is the issue is that nobody so far appears to have done a thorough investigation...although measuring a pressure drop across a drier was a good move. However, if a drier plugs up, that's a sign someone working on the system in the past may not have used proper procedures regarding brazing and/or evacuation (vacuuming).

    But now you're saying that this crew removed the old evaporator BEFORE they realized they couldn't get the replacement up the attic access stairs? Or did they realize that fact prior to removing the old evaporator?
    Yes, they removed the 8 month old evaporator before they brought up the new evaporator. I had begged Sam the boss from Heck, not to mess with the evaporator, because nobody said it was bad, and ther was a high probability that they, Axtil, will create new problems in the process.

    There's no reason to change an entire evaporator coil if it's not leaking. If there's a restriction it will likely be in the metering device just prior to the evaporator, since it is the smallest portion of the entire refrigerant loop other than the driers, which are actually filters with desiccant included.

    If by some miracle the parade of techs cycling through your mother's system get the refrigeration portion of her system working perfectly, and the evaporator STILL freezes up, then that's an airflow problem, period. Getting that resolved will mean finding somebody who understands duct design and layout, who is a person as rare as hen's teeth, it seems.
    We already suffered from 2 of the 3 years this new Rheem system has been running, due to low airflow. It eventual caused so much vibration at the compressor that is shook all the outdoor unit's anchor bolts out of the tapped holes in the anchors ... all but one of the four bolt were dancing on the floor of the outdoor unit. I used the excellent install instructions, and determined that when they installed my Mother's old simple analog thermostat after the 1st year of operation, they forgot to change the dip switches on the air handler, so she never ran on the high speed for 2 years, and was constanty beating on the compressor.

  12. #38
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    Aug 2003
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    Fort Worth, TX
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    Quote Originally Posted by KevimK2 View Post
    Yes, they removed the 8 month old evaporator before they brought up the new evaporator.
    Unbelievable. So what has happened in eight month's time that the evaporator in the attic can fit through the access hole but the one that is supposed to replace it cannot fit?


    We already suffered from 2 of the 3 years this new Rheem system has been running, due to low airflow. It eventual caused so much vibration at the compressor that is shook all the outdoor unit's anchor bolts out of the tapped holes in the anchors ... all but one of the four bolt were dancing on the floor of the outdoor unit. I used the excellent install instructions, and determined that when they installed my Mother's old simple analog thermostat after the 1st year of operation, they forgot to change the dip switches on the air handler, so she never ran on the high speed for 2 years, and was constanty beating on the compressor.
    I doubt just running the blower on low speed caused her compressor to strain at the bolts. Sounds to me like a gross overcharge or a system full of air and moisture vs. a mere dip switch blunder. And now they're chasing their own tails without ever sitting down long enough to target the source of ALL of your headaches and correct it. If they don't find the core problem, stand by for lather - rinse - repeat.
    • 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. #39
    Join Date
    Jul 2011
    Location
    Delaware
    Posts
    29
    One correction where I was not clear enough: They removed the 8 monnth old evaporator for reasons unknown (it was not leaking), and they left it in the attic, after they found that they could not figure how to get it down the typical folding stairs from the garage ceiling. That stairway is how the 8 month old evaporator was put in the attic. They would not attempt to bring the new (allegedly identical) evaporator up the stairs and risk damaging it, until they figured out how to get the old one down.

    Bottom line, going on 2nd day of no-cooling for my 89 yo Mom, due to problem installing a new evaporator that may not have been needed! Doh!

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