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  1. #1
    Join Date
    Nov 2005
    Posts
    15
    New install on 3.5 ton 12 SEER with 4 ton coil with no expansion valve used. .078 orifice only.

    53 psi Suction line
    176 psi high line
    75 degree ambient temp at condenser
    40 degree suction line temp at condenser and at coil
    40 degree supply vent temp at all vents
    80 degree high line temp

    Obviously the suction line pressure and temp are both too low. And the suction line is 40 degrees and sweating the entire length from condenser to coil.

    No obvious kinks in suction line. But the pressing notion of a restriction exists due to the low pressure. However, if the restriction were in the suction line, wouldn't there be a temp difference at both sides of the restriction. Yet the temp is consistent the entire length. I'm thinking a restriction in a feeder tube in the coil.

    Any input would be appreciated.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,474
    Low airflow?

  3. #3
    Join Date
    Apr 2004
    Posts
    7,680
    Sounds like no load, whats the indoor WB and whats the airflow? (Actual CFM).

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,390
    Originally posted by funthea
    75 degree ambient temp at condenser

    Any input would be appreciated.
    L.O.L.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  5. #5
    Join Date
    Nov 2005
    Posts
    15
    I understand there is no real load with an ambient of 75 and the WB of 70 but should this render a suc temp of 40 and result in the low suc pressure?

  6. #6
    Join Date
    Nov 2005
    Location
    W.WA
    Posts
    10
    Yes

  7. #7
    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 __

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,390

    Ambient & Load

    Originally posted by funthea
    I understand there is no real load with an ambient of 75 and the WB of 70 but should this render a suc temp of 40 and result in the low suc pressure?
    AIRFLOW ___ CFM ?
    Is Room Temp already < 72'F?
    Is Evap. L.A.T. < 54'F?

    What was the Vacuum Pressure and
    duration prior to adding charge?

    Seems like suction pressure is 'just slightly' low given almost no load with the discharge pressure Significantly low.

    IF you can not test at 82'F +,
    Turn the OVEN On for a few hours with the door Open.

    + come back in May. RE-Test in ANY Event.

    AT 75 CT __ DT __
    RT __ ST 40 DT __
    IWB __ IDB __

    Evap ST __ LT __
    Comp A __ Rated A __
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #9
    Join Date
    Apr 2003
    Location
    Iowa
    Posts
    763
    are you sure you have enough in it yet? seems like everything is low on it.

  10. #10
    Join Date
    Feb 2005
    Location
    Dothan, Al
    Posts
    3,453
    Originally posted by BaldLoonie
    Low airflow?

    I agree with Baldy, low air flow - suction line should be no more than 20 - 24 degrees below IAT. IMO

    Richard

  11. #11
    Join Date
    Nov 2005
    Posts
    15
    Thanx for all the replies. I'll get back with the info you have all requested when I get home. For now as far as the questions I can readily answer... The cfm is a result of a return of 286 sq. in. grill vent and a supply of 14" diameter round. Air seams to blow quite nicely from room vents at 40-42 degrees. And yes the room temp was 72 degrees as was the return air going into the furnace.

    My fear is that I have liquid refrigerant going into the suction line that could damage the compressor.

  12. #12
    Join Date
    Nov 2005
    Posts
    15
    Originally posted by airconman
    are you sure you have enough in it yet? seems like everything is low on it.
    I would have believed I was low on refrigerant too, as I did not put any in.

    The Airease unit claimed to be charged with enough to cover 20 ft of line and I added 45 ft of line. I did not add any because the vent air temp was colder that I would have expected, the suction line temp was colder than I would have expected and the LP was what I thought it should be.

    I thought I had a restriction in one of the feeder tubes in the evap. This would cause all the liquid refrigerant to only use the tubes that weren't restricted resulting in a flooding of the tubes that weren't restricted and a situation where not all of the liquid could evaperate. Thus causing the suction line to take on liquid refrigerant. This would explain why the suc line is so cold and sweating... I thought.

    [Edited by funthea on 11-02-2005 at 03:35 PM]

  13. #13
    Join Date
    Feb 2005
    Location
    Dothan, Al
    Posts
    3,453
    Originally posted by funthea
    "I would have believed I was low on refrigerant too, as I did not put any in."

    Richard: You may be slightly low, but that is not yur immediate problem. Fix the problem and then recheck yur charge


    "I thought I had a restriction in one of the feeder tubes in the evap. This would cause all the liquid refrigerant to only use the tubes that weren't restricted resulting in a flooding of the tubes that weren't restricted and a situation where not all of the liquid could evaperate. Thus causing the suction line to take on liquid refrigerant. This would explain why the suc line is so cold and sweating... I thought."
    [/B]
    No, a restriction will cause a reduction in the amount of refrigerant entering the evap., thus causing a reduction in pressure / sat.temp, but the superheat will be higher, keeping the suction temp up.
    The only thing that I know of that would cause yur conditions is low airflow through the coil, or an expansion valve overfeeding the coil.

    Hope this helps,
    Respectfully,
    Richard

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