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  1. #14
    Join Date
    Feb 2010
    Location
    Northeast, PA
    Posts
    235

    Old School

    Hey, for 21 yrs I have heard to charge an R-22 system to 30 deg above ambient temperature on the dishcharge gauge, guess what it did work on the old systems (I use superheat or manufacturers charging chart) and after charging a system sometimes it would match up. But now you get into the high efficiency systems and there not even close sometimes, I remove refrigerant from systems all the time to get the superheat. So the moral of the story is learn the proper way now and it will save you and customers alot of compressor failures. You will be amazed how fast you will get used to it, and you will never hook up to a system without checking the superheat and subcooling. It will make you a better technician.

  2. #15
    Join Date
    Mar 2011
    Location
    far southwest chicago suburbs
    Posts
    133
    I was lucky enough to have been taught about charging to superheat or subcooling in school. With dual thermometers or gauges with 2 temperature clamps I just automatically check both every time and take note. Lets you know a lot. If you have a house that is 90 degrees inside then 75 psi will probably not be close. Again you need to check everything to understand what the system is doing.

  3. #16
    Join Date
    May 2011
    Location
    Houston, Texas
    Posts
    67
    Thanks, some of you guys are really compassionate and honest about this trade.

    Note to self: Reread Superheat and Subcooling this weekend!
    (Oh yeah! I definitely going to get that new Fieldpiece Gauge!)

  4. #17
    Join Date
    Oct 2010
    Location
    SW Michigan, near Battle Creek
    Posts
    921
    yeah taking superheat and subcool as standard procedure is the way to go. and write down what the numbers are before you change annything.

    The thing I see is techs not waiting long enough to get true superheat readings. the books say 10 minutes and I think that is true. subcool seems to settle down faster.

  5. #18
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    955

    Systems

    of old were very forgiving. From what I saw when I first got in this trade, most systems were over-charged. As long as the system cooled, the customer didn't care. Now, everyone wants a system that will not only cool and de-humidify, but also be energy efficient while doing it. The only way to acheive this is have a properly installed and charged system following the manufacturers guidelines and using state-of-the-art test equipment. It used to be you could tune a car by changing the plugs, setting the gap with a dime, and setting the points with a matchbook cover. Try doing THAT today. Same holds true for HVAC systems. Do the job right by superheat, sub-cool, and proper airflow.

  6. #19
    Join Date
    Mar 2010
    Location
    Arnold, Mo
    Posts
    415
    Quote Originally Posted by seanhoang View Post
    My boss taught me that charging a system about 70 when ambient is cool and 75 when ambient is hot, should be "within range" and system should work fine. I did asked him once why not charged the system via superheat and he said that only if he feels he needs to.

    Just wandering if this is still acceptable in the trade and do most pros do that or never.

    Thanks, Sean.
    Does your boss ever use the phrase "beer can cold"? That doesn't work either.

  7. #20
    Join Date
    Dec 2009
    Location
    maroon lazyboy
    Posts
    1,048
    Quote Originally Posted by flanders View Post
    Does your boss ever use the phrase "beer can cold"? That doesn't work either.
    yeah... like the other day...

    new a/c in a trailer house.... 98F outside and at least that hot in the trailer itself....

    If I would have charged that to "beer can cold", It would have been WAAAAAAAY over charged.

  8. #21
    Join Date
    Oct 2010
    Location
    SW Michigan, near Battle Creek
    Posts
    921
    guilty secret. Fixed orifice systems work better around here if slightly overcharged.

    The book is the same in New Mexico or Alaska. In Michigans low temp and high humidity I have gotten more than one call back because the system "doesnt cool as well" after I reduced the charge to the book. Add a 10-20% overcharge back in everybodys happy.

  9. #22
    Join Date
    Feb 2011
    Location
    Orange County, in a Galaxy far far away...
    Posts
    277
    I think I'm the only one in my company who connects gauges, thermometers, takes indoor temps and split while unit is getting up to speed and then jots down superheat or subcool readings.

    Sman3 gauges are awesome but I'm too broke to buy them. They also remove a lot of the thinking required of a technician when diagnosing and charging.
    You cannot cheat an honest man. But that doesn't stop people trying!

  10. #23
    Join Date
    Oct 2010
    Location
    SW Michigan, near Battle Creek
    Posts
    921
    Quote Originally Posted by knave View Post
    yeah... like the other day...

    new a/c in a trailer house.... 98F outside and at least that hot in the trailer itself....

    If I would have charged that to "beer can cold", It would have been WAAAAAAAY over charged.
    beer can cold would probably be impossible.

  11. #24
    Join Date
    Feb 2010
    Location
    Northeast, PA
    Posts
    235
    Quote Originally Posted by fearlessfurnace View Post
    guilty secret. Fixed orifice systems work better around here if slightly overcharged.

    The book is the same in New Mexico or Alaska. In Michigans low temp and high humidity I have gotten more than one call back because the system "doesnt cool as well" after I reduced the charge to the book. Add a 10-20% overcharge back in everybodys happy.
    Wouldn't a fan cycle control do the same thing but a little more efficiently ?

  12. #25
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,579
    Quote Originally Posted by TriWorksInc View Post
    Wouldn't a fan cycle control do the same thing but a little more efficiently ?
    At what cost to install?

  13. #26
    Join Date
    Aug 2011
    Location
    Ohio
    Posts
    49
    In school we were not even taught the method the OP posted. The only time my teacher and I charge any different than the manual states is when we use Enviro Safe. Then we charge by the refrigerant manufacturers instructions. I know efficiency changes everything, in school we learned (if my memory is correct) that condenser split should be around 30 if the SEER is below 5, 20 between 5 and 9, and 10 if above 9 SEER. I may be off on the numbers a bit but I do know one rule of thumb does not work for everything all the time so I take the time to do it right. I am just starting out so I want to do everything the right way and build a reputation so I don't take short cuts unless my teacher says so (he is in charge).

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