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  1. #27
    Join Date
    Dec 2007
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    Ohio
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    2,876
    Quote Originally Posted by hvac-master View Post
    1) A 13 SEER American Standard would utilize a TXV and would require the subcooling to be tested for system charging.
    2) This system has a factory installed drier and would not require an external drier.
    3) You do not need to check the charge at every preventive maintenance to perform it correctly. Why do you want to remove refrigerant every year when removing your 6' hoses? Take the time to verify and maintain airflow. The air conditioner is a sealed system and will not require refrigerant unless a leak is present.
    How would you know if a leak has developed without checking the superheat / subcool on every inspection?? I do and will check charge EVERY time...the point of PREVENTATIVE MAINTENANCE is to catch possible problems before they have time to develope.

    Also...just because you have a TXV doesnt mean that you shouldn't check your superheat...with it, you are only doing it half-azz...superheat can tell you alot about a system....ESPECIALLY one with a TXV.

    Spent the extra time on a call today....just a PM and found that the system was low on charge....will be returning on Monday to find the leak....and by the way....as of August of last year...the unit was working perfectly....now...do you think that the homeowner was glad that I checked the superheat today????
    I need a new signature.....

  2. #28
    Join Date
    Feb 2008
    Location
    Waffleville
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    10,339
    Quote Originally Posted by I_bend_metal View Post
    How would you know if a leak has developed without checking the superheat / subcool on every inspection?? I do and will check charge EVERY time...the point of PREVENTATIVE MAINTENANCE is to catch possible problems before they have time to develope.
    some people will argue that a delta "t" is as good as checking pressures. my last co was like that. another reason why they are my last co
    If Guns Kill People, Do Pencils Misspell Words?

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  3. #29
    Join Date
    Dec 2007
    Location
    Ohio
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    2,876
    Quote Originally Posted by beachtech View Post
    some people will argue that a delta "t" is as good as checking pressures. my last co was like that. another reason why they are my last co
    Anytime I work on an AC or HP....my gauges go on it!! What does it take about 10 minutes to check these things and make sure....for your homeowner's sake that everything is alright???
    I need a new signature.....

  4. #30
    Join Date
    Oct 2003
    Location
    Valdosta Ga
    Posts
    847
    I was not trying to be funny my experence is you cannot have the perfict charge when servicing at low outdoor ambent temps.

  5. #31
    Join Date
    Dec 2007
    Location
    Ohio
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    2,876
    Quote Originally Posted by bzzline View Post
    I was not trying to be funny my experence is you cannot have the perfict charge when servicing at low outdoor ambent temps.
    DAMN!! That reminds me....I took pics yesterday of my tent setup...then left the camera at the office!! I will get them posted soon....also from my next to last post....when I found that unit low on charge today...it was 40 degrees outside and 78 in my tent!!
    I need a new signature.....

  6. #32
    Join Date
    Jan 2008
    Location
    Elkton, MD
    Posts
    141

    Reality

    Quote Originally Posted by I_bend_metal View Post
    How would you know if a leak has developed without checking the superheat / subcool on every inspection?? I do and will check charge EVERY time...the point of PREVENTATIVE MAINTENANCE is to catch possible problems before they have time to develope.

    Also...just because you have a TXV doesnt mean that you shouldn't check your superheat...with it, you are only doing it half-azz...superheat can tell you alot about a system....ESPECIALLY one with a TXV.

    Spent the extra time on a call today....just a PM and found that the system was low on charge....will be returning on Monday to find the leak....and by the way....as of August of last year...the unit was working perfectly....now...do you think that the homeowner was glad that I checked the superheat today????
    The reality is that once a system has been installed you do not need to place a set of gauges on it to check superheat or subcooling unless you are less than confident in your brazing and leak test abilities.

    Confirm your airflow is 400 CFM per ton and perform a calculation of the installed total capacity(Measured CFM X 4.5 X Delta Enthalpy). Once you benchmark a systems capacity at installation it is very easy to determine when a future problem arises.

  7. #33
    Join Date
    Dec 2007
    Location
    Ohio
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    2,876
    Quote Originally Posted by hvac-master View Post
    The reality is that once a system has been installed you do not need to place a set of gauges on it to check superheat or subcooling unless you are less than confident in your brazing and leak test abilities.
    So what you are saying is that ONLY the spots that are brazed leak?? You have never found a leak in a coil? Oh and I don't braze...#8 Stay-Brite is all you need.
    I need a new signature.....

  8. #34
    Join Date
    Oct 2003
    Location
    Valdosta Ga
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    847
    Quote Originally Posted by I_bend_metal View Post
    DAMN!! That reminds me....I took pics yesterday of my tent setup...then left the camera at the office!! I will get them posted soon....also from my next to last post....when I found that unit low on charge today...it was 40 degrees outside and 78 in my tent!!
    There are alot of times when it's 105 you have to let some spring service out even after all the freon fine tuning

  9. #35
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,350
    Quote Originally Posted by hvac-master View Post

    Confirm your airflow is 400 CFM per ton and perform a calculation of the installed total capacity(Measured CFM X 4.5 X Delta Enthalpy). Once you benchmark a systems capacity at installation it is very easy to determine when a future problem arises.
    This works as long as the system is tested under similar conditions in the future. Same airflow, not diminished by dirty coils/filters/blower wheels, same outdoor temperature, same indoor heat load, same indoor wet bulb. Otherwise, there will be variance from the initial capacity check. Perhaps not significant deviance, but the only time a system is said to be operating at rated/nominal capacity is when it is under ARI rating conditions, which are 95 degrees outdoor dry bulb, 80 degrees indoor dry bulb, 67 degrees indoor wet bulb. Since many of us prefer 75 degrees dry bulb and 55 or lower degrees indoor wet bulb, the actual operating capacity, even when outdoor ambients are at 95, will be other than nominal.

    For the OP, I must agree with others who have stated the evidence you've presented so far...a technician with a mostly upside-down refrigerant bottle being startled upon your arrival...is not enough to assume your system has an incorrect charge. Personally, if I were concentrating on charging your system properly and you came up behind me without making much sound, I might jump with a start as well once I realized you were there. It's just a natural reaction to the unexpected.

  10. #36
    Join Date
    Jul 2005
    Posts
    5,574
    Quote Originally Posted by hvac-master View Post
    The reality is that once a system has been installed you do not need to place a set of gauges on it to check superheat or subcooling unless you are less than confident in your brazing and leak test abilities.

    Confirm your airflow is 400 CFM per ton and perform a calculation of the installed total capacity(Measured CFM X 4.5 X Delta Enthalpy). Once you benchmark a systems capacity at installation it is very easy to determine when a future problem arises.
    I don't lose any freon checking the charge. Always empty the hoses back in to the low side before pulling them loose. The quantity of refrigerant vapor left in the hoses will be absolutely insignificant. If the set doesn't leak, then it will even be less than insignificant because the static pressure in them will be about the same when you leave as it was when you got there.

    Benchmarking is good for factory engineers. Not good for resi service. We don't have time to wait for indoor and outdoor conditions to repeat themselves, and when these are different capacity is also different. Capacity isn't a constant, not by a long shot. I have a chart and a slide rule, either of which will determine whether air volume is in the correct range as long as the charge is ok, but you have to confirm a proper charge before using it.
    Charge is more critical than air volume, and it is difficult to accurately measure air volume to the precision required for you to determine charge levels by differences in enthalpy. If your calculation is only very slightly off, then you could lose a compressor because you didn't do something as simple as check superheat.
    Last edited by hvacrmedic; 03-15-2008 at 01:40 AM.

  11. #37
    Join Date
    Jan 2005
    Posts
    159
    OP: I guess since that was a joke that meant more to the people in the trade, I guess that's why I didn't get it. --Sorry!

    I appreciate hearing all the techs say that doing a superheat & subcooling check is part of what they'll do as part of a PM. That's exactly what I wanted to hear - of all the people I've had out over the years, none have done a superheat / subcooling calculation.

    Now I just need to find just such a firm to do my PM.

  12. #38
    Join Date
    Dec 2002
    Location
    Toledo, Ohio, United States
    Posts
    12,911
    Twilli says whats superheat, we don't need that on Colemans
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  13. #39
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,171
    Quote Originally Posted by twilli3967 View Post
    Twilli says whats superheat, we don't need that on Colemans
    You will on the new 13 SEERs. they've gone back to pistons.
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