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  1. #14
    Join Date
    Nov 2005
    Posts
    15
    Originally posted by jultzya
    Let's start here, here, here, & here.

    Then try to give as much of this as possible...

    Make: __
    C Model number: __
    E Model number: __
    Evap Metering Device: PISTON

    SP 53 /T 28 ST 40 SH 12
    LP 176 /T 92 LT 80 SC 12
    AT 75 CT __ DT __
    RT __ ST 40 DT __
    IWB __ IDB __
    Evap ST __ LT __
    Comp A __ Rated A __


    Make: __Airease
    C Model number: __SCU12G42A
    E Model number: __C2E46B-2A
    Evap Metering Device: PISTON .078

    Retested numbers

    SP 57 /T 32 ST 42 SH 10
    LP 155 /T 85 LT 70 SC 15
    AT 69 CT __ DT __
    RT __ ST 40 DT __
    IWB __ IDB __
    Evap ST 40 LT 67
    Comp A __ Rated A __

    Not sure what the rest of your abreviations are but the Condenser discharge air temp above fan is 77
    Return air at furnace is 68
    Supply air out of evap is 42
    Delta temp is 26 indicating low flow as many of you guys have suggested.
    Evap temp is then 27 with fear of freezing
    I do not have dry and wet bulb thermocouples

    as far as the air flow goes, as I stated earlier I have a 286 sq.in. return grill and the supply is a 14" round plentum of 154 sq.in. Off of the 14" duct is a 10" duct that turns into two 8" ducts. Also there are two 5" ducts and one 6" duct that feed two regiters. All the others only feed one register each.



  2. #15
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,848
    The Condenser discharge air temp above fan is 77.
    > WHAT, with a 75 ambient that is only aa 3-degree delta-T!
    Return air at furnace is 68
    Supply air out of evap is 42
    Delta-T temp is 26 indicating low airflow as many of you guys have suggested.
    Evap temp is then 27 with fear of freezing

    A 3.5-ton condenser, 4-ton cooling coil.
    Has 286-sq.in. return grill and the supply is a 14" round plenum or 154 sq.in. Off of the 14" duct is a 10" duct that turns into two 8" ducts. Also there are two 5" ducts and one 6" duct that feed two registers. All the others only feed one register each.

    The 3.5-ton system ought to have a 20” round 350-sq.in. Main Supply and Return Trunks.
    A 22” 380-sq.ins. Return wouldn’t hurt a thing.
    What do you have for an air handler?
    Test every aspect of the airflow, and get it right!
    Use the Manual D.

    http://www.udarrell.com/proper_cfm_b...g_systems.html

  3. #16
    Join Date
    Nov 2005
    Posts
    15
    Originally posted by udarrell
    The Condenser discharge air temp above fan is 77.
    > WHAT, with a 75 ambient that is only aa 3-degree delta-T!

    No, that ambient temp was from the first test posting. The subsequent numbers were from the second testing. The ambient that pertains to that test was 68 degrees for a delta temp across the condenser of 9 degrees.

    Your correct that I have some serious air flow issues to rectify.

  4. #17
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,820
    Just for grins pull the blower door off the furnace and see what happens. of course you will have to hold or tape the switch temp.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  5. #18
    Join Date
    Jan 2003
    Posts
    959

    maybe low

    I find it very hard that the suction line temp and the out comming off the a coil are the same. How long is the line set you are using. If its more than 25' you need more freon.
    Let unit run a while and stablize. make sure there is no restriction on air flow. I have had the paper that comes with the a coil get caught up into the a coil.

    Another trick I use is I listen to the liquid line at the a coil. if its full you will get a smother steady sound if it is not then you will hear it be unstable as if it is staving for liquid.

    Did you pull a good vacum on the system?

    regards,
    Kelvin

  6. #19
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,820

    Re: maybe low

    Originally posted by klyons20
    Another trick I use is I listen to the liquid line at the a coil. if its full you will get a smother steady sound if it is not then you will hear it be unstable as if it is staving for liquid.
    Dang I knew I should not have thrown my stethoscope away, in 30 years I have never heard of that trick, learn something new everyday.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  7. #20
    Join Date
    Jan 2003
    Posts
    959

    hear it...

    Well, if its low and or something in there besides freon you can hear it..

    regards,
    Kelvin

  8. #21
    Join Date
    Nov 2005
    Posts
    15

    Re: maybe low

    Originally posted by klyons20
    I find it very hard that the suction line temp and the out comming off the a coil are the same. How long is the line set you are using. If its more than 25' you need more freon.
    Let unit run a while and stablize. make sure there is no restriction on air flow. I have had the paper that comes with the a coil get caught up into the a coil.

    Another trick I use is I listen to the liquid line at the a coil. if its full you will get a smother steady sound if it is not then you will hear it be unstable as if it is staving for liquid.

    Did you pull a good vacum on the system?

    regards,
    Kelvin
    Thanx for the reply Kelvin.
    Yes, the suction line leaving the evap, all the way to the condenser is the same as the supply air from the register closest to the evaporator. The line set is 45'. I did not add any freon because of the numbers I was getting. Also, if I was low on freon wouldn't the superheat be high instead of low?
    I added 400 CFM more air flow, even though I know it is still low. I now have a total of 1055 CFM. From what I have read, the lowest I should ever have is 1347. But I know of other people that are 15% short of there projected minimum CFM flow that are not having the problem I am having.
    As far as hearing the liquid line, I try that. Also I suppose there could be paper stuck up in the evaporator, I don't remember checking up there when I installed it. Also I pulled a 30 hg vacuum for over an hour.
    Thanx.

  9. #22
    Join Date
    Oct 2004
    Posts
    3,400

    Re: Re: maybe low

    [QUOTE]Originally posted by funthea
    I pulled a 30 hg vacuum for over an hour.

    ???

  10. #23
    Join Date
    Feb 2005
    Location
    Dothan, Al
    Posts
    3,453

    Re: Re: maybe low

    [QUOTE]Originally posted by funthea
    Thanx for the reply Kelvin.
    "Yes, the suction line leaving the evap, all the way to the condenser is the same as the supply air from the register closest to the evaporator."


    This is due to the evap being full of liquid ( low superheat ) - when full, the supply air will be the same temp as the suction line. Matter-of-fact,I usually like to se only a 3-5 degree difference between the two. when I am charging. ( if humidity is not high )


    "I did not add any freon because of the numbers I was getting."


    I'm certainly glad you didn't, refrigerant level is not the problem.



    "I added 400 CFM more air flow, even though I know it is still low. I now have a total of 1055 CFM. From what I have read, the lowest I should ever have is 1347. But I know of other people that are 15% short of there projected minimum CFM flow that are not having the problem I am having."


    Did this improve the readings, or were the last set after you increased airflow?? eg' - suction temp go up, suction press go up ??
    I believe that you need to get the proper airflow ( max amount ) and then lets see what the system measurements are.

    Respectfully,
    Richard

  11. #24
    Join Date
    Nov 2005
    Posts
    15

    Re: Re: Re: maybe low

    [QUOTE]Originally posted by bwal2
    Originally posted by funthea
    I pulled a 30 hg vacuum for over an hour.

    ???
    Ok, I used a two stage pump that claimed to pull to 100 microns. The gauge set that I was using only goes as low as 30 hg and it was maxed. I had pressure tested the system at 150 psi for over an hour before applying the vacuum. Although I did not measure the micron scale, I equated that since it held the 150 psi and the pump claimed to go down to 100 micron and the gauge set was maxed at its 30 hg reading. I figured it was good.

  12. #25
    Join Date
    Nov 2005
    Posts
    15

    Re: Re: Re: maybe low

    [QUOTE]Originally posted by bornriding
    Originally posted by funthea
    Thanx for the reply Kelvin.
    "Yes, the suction line leaving the evap, all the way to the condenser is the same as the supply air from the register closest to the evaporator."


    This is due to the evap being full of liquid ( low superheat ) - when full, the supply air will be the same temp as the suction line. Matter-of-fact,I usually like to se only a 3-5 degree difference between the two. when I am charging. ( if humidity is not high )


    "I did not add any freon because of the numbers I was getting."


    I'm certainly glad you didn't, refrigerant level is not the problem.



    "I added 400 CFM more air flow, even though I know it is still low. I now have a total of 1055 CFM. From what I have read, the lowest I should ever have is 1347. But I know of other people that are 15% short of there projected minimum CFM flow that are not having the problem I am having."


    Did this improve the readings, or were the last set after you increased airflow?? eg' - suction temp go up, suction press go up ??
    I believe that you need to get the proper airflow ( max amount ) and then lets see what the system measurements are.

    Respectfully,
    Richard
    Thax Richard for your reply. Yes I was of the same belief as you as far as the evap is full of liquid and heading back to the condenser.
    After adding the additional 400 CFM the only change I saw was that my delta temp at the evaperator changed from 30 to 22 degrees. But the suction line temp of 42 remained a problem. I am going to pop open the evap to see if there is paper in there as Kelvin noted.

  13. #26
    Join Date
    Oct 2004
    Posts
    3,400
    [QUOTE]Originally posted by funthea
    ... The gauge set that I was using only goes as low as 30 hg and it was maxed...
    (If you find a vacuum gage that reads deeper than 30"hg, I would like to see it.)


    Did you get airflow established?

    It really souds like that's the most likely suspect.

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