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  1. #1
    Join Date
    Dec 2007
    Posts
    26

    Looking for SH and SC guidelines

    Hi I am new to this field.
    I am familiar with charging a system using superheat and subcool levels based on manufacturer's performance chart.

    What do you guys do when the chart is missing or ruined by age/water/bugs.
    I am talking about residential units less than 5T.

    Is there safe, general rules to use for SH and SC?

    How about TXV vs. cap tube systems?

    Would the levels be different for R-22 vs. R-410A?

    I know it is not the best way to ball-park it, but if in a jam it'd be good to know a safe level to start.

    Thanks for your help.

  2. #2
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by kbm View Post
    Hi I am new to this field.
    I am familiar with charging a system using superheat and subcool levels based on manufacturer's performance chart.

    What do you guys do when the chart is missing or ruined by age/water/bugs.
    I am talking about residential units less than 5T.

    Is there safe, general rules to use for SH and SC?

    How about TXV vs. cap tube systems?

    Would the levels be different for R-22 vs. R-410A?

    I know it is not the best way to ball-park it, but if in a jam it'd be good to know a safe level to start.

    Thanks for your help.



    #1. you gotta get 15 posts and apply for pro membership. We can help you out a great deal there.


    #2. Its called tech support. Don't be afraid to call tech support to get this vital information. A truely honest tech won't hesitate to call when he/she is unshure of information.


    There isn't really a rule of thumb. I hate rule of thumb. It will only get you into trouble. You've got a phone, use it. You gotta let the system run anyhow to balance out. So spend that time on the phone with tech support.

    Another idea......write it all down. If you start now, you should have a nice little reference guide by summers end.


    Good luck. Have fun. Get to pro. And then we'll have a lot of fun
    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.

  3. #3
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    oh yeah....

    1 more thing.

    You can get superheat/subcooling calculators from a lot of supply stores. Exactcharge also has one that can be loaded onto a PDA.
    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.

  4. #4
    Join Date
    Dec 2007
    Posts
    26
    Is this calculator that will give you a estimated SH, SC based on size and rating of the equipment?

    No doubt calling the support folks to get right info for unit is best way. But sometimes, say late night or special locations or old stuff, it may not be possible.

    Just checking with you guys that are doing it.
    I know people that don't even use SC/SH.

  5. #5
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    no. The calculators that I have.....

    you use a slide calculator. First two are....

    indoor ambient temp (DB/WB)
    outdoor ambient temp (DB/WB)

    with these in line, you will be able to read target superheat.

    then you slide arrow of target superheat to calculated number and then start looking at temps and pipe temps. It even tells you when to add or remove refrigerant.


    Subcooling is always based off man. specs.




    But remember, all the pressures, temps, and SH/SC in the world won't help you one bit if the airflow is the problem.
    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.

  6. #6
    Join Date
    May 2005
    Location
    Lake County,Illinois
    Posts
    38

    calculators

    Carrier and most other dealers have these slide calculators available either for free or for a small fee I have found as i am sure most of the experienced techs have come to find that superheat based on indoor return wet bulb and outdoor dry bulb for both 22 and 410 a to be the same and whn looking for the subcooling as long as what you are looking for then the only thing that has changed is the pressure/temp readings

  7. #7
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    http://www.exactcharge.com/

    check it out. I have the software and its worked out really well for me. I mainly use the pressure/temp charts.
    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.

  8. #8
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,910
    Twilli says thermostat
    No Heat No Cool You need Action Fast

  9. #9
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by twilli3967 View Post
    Twilli says thermostat
    Don't mind Twilli.........

    hes very consistent with the random words coming out of his keyboard
    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.

  10. #10
    Join Date
    May 2005
    Location
    Lake County,Illinois
    Posts
    38
    Quote Originally Posted by iraqveteran View Post
    But remember, all the pressures, temps, and SH/SC in the world won't help you one bit if the airflow is the problem.
    Good point, We have a new guy who just began getting comfortable charging 410a units and he called me up asking questions and based on what he was telling me i told him he was still undercharged and because he was adjusting the charge on a 5 ton system that had 1 1/8 line 60 foot run it would take a while 2 hours later and he said it didnt look right so i went out there and found the fan was running very low airflow across the coil, even though his subcooling would seem right his superheat and suction pressures were showing a restiction across the coil, something that is more or less learned and th charts dont really tell you!

  11. #11
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by castillo7411 View Post
    Good point, We have a new guy who just began getting comfortable charging 410a units and he called me up asking questions and based on what he was telling me i told him he was still undercharged and because he was adjusting the charge on a 5 ton system that had 1 1/8 line 60 foot run it would take a while 2 hours later and he said it didnt look right so i went out there and found the fan was running very low airflow across the coil, even though his subcooling would seem right his superheat and suction pressures were showing a restiction across the coil, something that is more or less learned and th charts dont really tell you!
    EVERYTHING IS LEARNED.

    What you need to tell the new guy is to leave his guages in the truck. Once he has looked at EVERYTHING........then he is allowed to check pressures and SH/SC to verify the system is running properly.
    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.

  12. #12
    Join Date
    Dec 2007
    Posts
    26
    Quote Originally Posted by iraqveteran View Post
    http://www.exactcharge.com/

    check it out. I have the software and its worked out really well for me. I mainly use the pressure/temp charts.
    I like this. Will check it out. Thanks for sharing.
    When I googled it, it is around $74 for the software.

  13. #13
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by kbm View Post
    I like this. Will check it out. Thanks for sharing.
    When I googled it, it is around $74 for the software.
    There is a gentleman on this site that I believe is the creator of the software. If you speak with him......he may give you the software free.

    I talked with him and got it free. All I did was sent him an email. He said get the PDA and let him know. I bought a used PDA of Ebay and he sent me software free.
    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.

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