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  1. #1
    Join Date
    Mar 2012
    Posts
    16

    HELP! Old AC not cooling well enough... recharge help?

    It's extremely hot here in Illinois with highs of around 100-105 and my compressor is having a difficult time getting my home temps under control. Just got my electric bill and it's $250 for about 2100kwh. Normal house utilization is around 900-1000kwh/mo when not running the AC. The AC is an 8.2 SEER Heat Controllers that's probably a 70s setup. I have an estimate for a new system but just haven't had the money with a new baby that's just arrived. We're having a hard time keeping the house at 75-76 and at those temps the AC is running non-stop when it's at it's hottest out. So.. I'd like to get some advice on whether or not you guys think getting someone out for a recharge will help or be worth it or if I'd be wasting money that could be saved to go toward the new system. If I can make it through Aug and Sept then I can save through the winter and replace it come spring. And if a recharge will get inside air temps colder then I know the savings over the next couple months could pay for it but otherwise I'm out money.

    Here is some more information...

    The inside furnace/air handler is a Trane XE90 installed in 04. The filter is clean and I'm using the more efficient crap, cheap green filters to improve airflow.

    The evap coil is clean as I've opened the cabinet to check it out. There aren't any air leaks that I've found in ductwork as I have full access in the basement.

    The Compressor coil is clean and I bought coil cleaner this year and sprayed it down and lightly power washed as to not damage the fins. A lot of nasty crap came out.

    I've owned the home for 5 years and when I bought it, the inspector said the AC had a 14 degree differential which was at the edge of the OK range. The air was definitely colder then than it is now.

    The airflow from the vents is good but the air temperature is just mildly cool. The temp of the inside air doesn't really seem to change much no matter how hot it is outside. It's 80 this morning and the inside AC air from vents feels about the same as it does later when it's in the 90s.

    When the HVAC company came and gave me an estimate, they said the fan on the compressor was running a little slow. It is a GE 0.7Amp 825rpm 1/12hp. It does have a piece of fabric hanging from the grill that looks to be used to monitor airflow that is hanging just above the fan blades while the fan is running. I feel pretty good warm airflow from the fan while it's running.

    As far as the compressor lines, the one covered in insulation is cold and sweating while the system is on. It's not an uncomfortable to hold cold but is cold. The smaller line is warm while the system is running.

    If there is any more info that I can give you, let me know, just trying to keep up with the heat and get through this miserable summer. I've never had so many weeks of constant 100 degree temps.

  2. #2
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,971
    It does sound like the indoor supply air is not having enough heat removed from it; that temp-split should be around 18-F under normal heatload conditions & @50% indoor humidity.

    The temp-split of the air coming off the outdoor condenser is also an important indicator of performance levels & clues to discover where problems may exist.

    Simple easy to do ways to check the performance of your central air conditioner so, if needed, you can call an Energy Efficiency HVAC Technician

    Performance Data Collection – Best Time to collect data is Late afternoon around 4:30 pm; also when outdoor temps are around 85; 95; 105F or, anywhere in between.

    *All U need is a good thermometer (digital reading in tenths preferable) & and indoor Humidity Gauge

    1) Helpful; Tonnage & SEER Rating of condenser & condenser's model number: ________

    2) Indoor Coil: TXV or, orifice metering device? _______ Only if U know.

    3) Outdoor condenser’s discharge-air-temperature _____

    4) Outdoor air temperature: _______

    5) Outdoor Condenser Air-Temp-Split _____

    6) Need the percent of humidity - away from Supply-Air outlets ______

    7) Indoor Return-Air Temperature ______ Subtract Supply-Air Temperature= Temp-split ______F

    8) Indoor temperature-split _______F

    --- Need the above information for performance analysis; example below:

    A Goodman 2-Ton 13-SEER condenser, 800-cfm indoor airflow @ 85-F outdoors; 80-F indoor dry bulb & 50% relative humidity = 103.9-F - 85-F outdoors or an 18.9-F temp-split; Indoor temp-split 18 to 19-F.;
    @ Indoor 75-F & 50% RH outdoor condenser split is close to 14.9-F

    If it's not close to the mfg'ers data U need to call a good Tech & explain your findings...if he seems puzzled call someone else.

    *I have an all electric farm home except for propane heating & for a record setting hot June, & I stayed perfectly COOL; my TOTAL JUNE electric bill was: June 30, 2012; Darrell’s ELECTRIC METER; 62610 – 62140= used 470-KWh * .0985= $46.295.

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