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  1. #19
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,974
    Quote Originally Posted by Cap'n Preshoot View Post
    Apologies for not getting back sooner. Here are the stats & info

    Condenser/Compressor Lennox 14ACX-036
    A Coil: Lennox CH33-44/48B -2 -F
    TXV

    Flwg data retrieved moments ago (12:30 PM Friday 8/24

    Outdoor condenser discharge air temp = 107.5
    Outdoor air temp = 91.7
    air split = 15.8 deg

    Indoor return air temp (at the attic plenum) 73.6
    Indoor supply air temp " " " " 60.6
    air split = 13.0 deg

    Relative humidity: Family rm 57% Master BR 64%
    Room temperature: Family rm 74.7 deg Master BR 70.1 deg
    Dew Point: Family rm 57.9 deg Master BR 58.5 deg
    Master BR is the coldest room in the house, but is the longest run but also has a 12 x 12 ceiling return air grille
    The home feels slightly humid.

    Taylor #9842 digital thermometer
    ExTech #445814 digital psychrometer

    addt'l info: The T-stat is in a hallway with the 20 x 30 main return along with an exterior door and a SE facing window (all morning & afternoon sun, but has a dark shade covering the window). We are able to achieve set-point of 75 deg in the hallway but if the set point is lowered, say to 74, system cannot keep up and the temperature in the hallway actually rises to 77 (as displayed on the T-stat) Thanks!!!!
    Comparing your data to a 14-SEER 3-Ton unit of another Make: the indoor temp-split of 13F appears to be not enough; even when using 63% RH & 1175-CFM this data says 16F split.

    At an indoor 75F dry bulb & 50% RH the indoor split should be close to 20F; I'd say @58% RH the indoor split ought to be near 17-F.

    Possible refrigerant system problem;an overcharge would produce a false higher pressure reading than the actual heatload transfer would be providing. Therefore, we have to look at the outdoor split with caution...

    The outdoor condenser split is on target using 50% RH but a little low using 58% RH; a higher latent/humidity load on the indoor coil increases the outdoor condenser split but decreases the indoor split.

    The difference between the two splits indicates possible problems.
    However, to pin point any problems we need the subcooling temperature & compressor amp-draw.

    Using the Lennox Approach Method; for the 14ACX it calls for 6-F (+/- 1-F) of condenser subcooling. The liquid line temp minus outdoor ambient = approach subcooling temperature.

    On non-accumulator Lennox A/C condensers with TXV metering devices the above method will indicate whether it's overcharged or undercharged according to their approach chart.
    Last edited by udarrell; 08-24-2012 at 07:12 PM. Reason: Word missing...(+/- 1-F)

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