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  1. #1
    Join Date
    Jun 2008
    Posts
    25

    Requesting a litle advice - ac correct r22 charge.

    Recently we had a new York furnace and evaporator coil (with txv) installed to replace aging units. We had it installed when it was still quite cold outside and I have a question regarding the freon R22 charge which was set after the coil was installed. The tech simply checked the charge by adjusting it to suction 65psi. I feel he should have set the charge by using the subcool method. I believe the outside temperature on the installation day was about 60 degrees. Should I insist that they come back to recheck the charge or is their "rule of thumb" method really good enough and to be trusted/accepted? The 65 degrees suction pressure is approx. 38 degrees at the evap coil, but is the system going to perform as it should?
    Thanks for your input!

  2. #2
    Join Date
    Mar 2008
    Location
    Grundy Co. IL
    Posts
    773
    I didn't know there was a rule of thumb, you might want to invite him back over.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,556
    They just guessed based on whatever.
    It should be checked by SC, SH, and temp drop across the coil.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    call them and get it checked

    that is not how to ajust anything and you may even be over charged

  5. #5
    Join Date
    Mar 2008
    Location
    Grundy Co. IL
    Posts
    773
    Quote Originally Posted by beenthere View Post
    They just guessed based on whatever.
    It should be checked by SC, SH, and temp drop across the coil.
    Does rule of thumb mean, if you put your thumb on the big line and it's cold, you're O.K.?

  6. #6
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by Jay 41 View Post
    Does rule of thumb mean, if you put your thumb on the big line and it's cold, you're O.K.?
    no.

    rule of thumb is two fold. You use your left thumb to check return air and right thumb to check supply air. Once done, return left thumb to arse and return right thumb to mouth. Be sure you do the L test before returning thumbs!!

    rule of beer states beer can cold is proper operatin levels for the cold stuff

    rule of wave states wave your hand in front of register. If you feel air coming out, you have proper CFM.



    And the final rule.......


    If the customer is happy, I'm haulin arse before they change their mind!!!!
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  7. #7
    Join Date
    Mar 2008
    Location
    Grundy Co. IL
    Posts
    773
    Quote Originally Posted by iraqveteran View Post
    no.

    rule of thumb is two fold. You use your left thumb to check return air and right thumb to check supply air. Once done, return left thumb to arse and return right thumb to mouth. Be sure you do the L test before returning thumbs!!

    rule of beer states beer can cold is proper operatin levels for the cold stuff

    rule of wave states wave your hand in front of register. If you feel air coming out, you have proper CFM.



    And the final rule.......


    If the customer is happy, I'm haulin arse before they change their mind!!!!
    Nice, very nice, thanks for the in depth answer.lol

  8. #8
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Here's the formula he was using....


    Outdoor Ambient
    (minus)
    Indoor Wetbulb
    (plus)
    Physical weight of unit
    (plus)
    Ounces in a 12 pack
    (minus)
    Technician's I.Q.

    Equals 65




    Just call him back and make him do it right.
    I need a new signature.....

  9. #9
    Join Date
    Mar 2008
    Location
    Grundy Co. IL
    Posts
    773
    Quote Originally Posted by I_bend_metal View Post
    Here's the formula he was using....


    Outdoor Ambient
    (minus)
    Indoor Wetbulb
    (plus)
    Physical weight of unit
    (plus)
    Ounces in a 12 pack
    (minus)
    Technician's I.Q.

    Equals 65

    Just call him back and make him do it right.
    Holy s***, these formulas get better every time, anybody else got one.

  10. #10
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by Jay 41 View Post
    Holy s***, these formulas get better every time, anybody else got one.
    Sure


    Outdoor Ambient Temp (DB) + Amount of service calls to run + Mileage to customers house + Diagnostic + Cost of gas + High Side PSIG (after gassing unit) = new hourly rate.


    multiply new hourly rate times amount of time invested in customer(including travel time to and from BFE) and you get new subtotal.

    Take our usual 85% off the top and hand to the rest into the boss. Don't forget to water the bushes at no extra cost.
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  11. #11
    Join Date
    Oct 2006
    Posts
    28
    Only By Subcooling If Is Txv Sys At Least 60 F Ambiant!!!!!

  12. #12
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,022
    Quote: "By Subcooling, if it is TXV Sys At Least 60 F Ambient." (True, & more)

    First, charge is only done & accurate, if airflow is within specifications.

    Superheat should also be checked to see if it is holding near its setpoint.

    If there is also very low indoor load on the coil the Subcooling will not be accurate & the Superheat will not hold its setpoint.

    A standard TXV "loses load adjust-ability" at about 30% of its rating.
    Balanced port TXV's lose load adjust-ability at about 15% of rating.

    Let me know if you have data directly contradicting those statements!
    http://www.udarrell.com/ac-trouble-s...ubcooling.html
    - udarrell

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