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Thread: R410a system

  1. #1

    R410a system

    Hello guys.... Thought I could use your help? Had problem with house cooling down ok, I did not install this new system was put in oct anyway this is a service call house will not cool down here is what I found.
    System is a 410a 2 1/2 ton sq ft of house is 1100
    Ranch with down flow system all low supplies to high returns sized ok for air. Has piston coil so I did super Heat on it.... WB 76 outside temp 100 Head pressure 400 suction pressure 145 suction line temp 82 tstat reading 85 in house supply discharge temp 65 house will not cool down.... Did notice no (attic fan) ..not pulling outside air from anywhere I can see. Condenser was effected by Sandy. Other contractor changed contacter I put new cap in ...amps were ok on compressor. I don't know what else to check..... Also I pumped system down and checked piston ok. Am I missing something? I don't know what else to check.... Please help....

  2. #2
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    Why is the humidity so high? That is why your supply temp is higher.

  3. #3
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    Your SH is too high, should only be 24, not 31. With the info you posted, it sounds like its still slightly low on charge.
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  4. #4
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    Have you checked insulation? Cfm readings across the evap correct? Acoil blockage? Wet bulb readings sound very high. Is unit running constantly?

  5. #5
    Hello... My return temp was 85 in return duct pulling back to furnace.... Supply discharge temp out of register 65.....was not cooling when I got ther that is why the house is so warm it was very warm outside 100 I waited about 2 hrs shoul have cooled down a little...... I was thinking getting outside air from somewhere but I could not find any?

  6. #6
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    Play with waynes brain ac anlyzer calculator @ efficientcomfort.net.

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  7. #7
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    sounds like u do have 20F delta T,usually mean system working fine,maybe something else u need to look at it beside the system!

  8. #8
    Pony.... I was thinking the something.... I keep going back to warm air being introduced from somewhere else?

  9. #9
    It's a lot cooler today outside I'll stop by there..... I need to look at attic location for roof fan I think that is part of problem. I'll see if house cooled down any.... Thanks guys for your help.

  10. #10
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    Quote Originally Posted by pony View Post
    sounds like u do have 20F delta T,usually mean system working fine,maybe something else u need to look at it beside the system!
    +1

    What about airflow? Is it moving 1,000CFM? If Delta T and airflow are both good then the system is OK.

  11. #11
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    Quote Originally Posted by 54regcab View Post
    +1

    What about airflow? Is it moving 1,000CFM? If Delta T and airflow are both good then the system is OK.
    So his saturated liquid line only being 17F above outdoor temp doesn't mean anything to you. Nor his SH being 7F too high. Both indicating the charge is probably low.
    Last edited by beenthere; 07-07-2013 at 10:33 AM.
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  12. #12
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    Quote Originally Posted by beenthere View Post
    So his saturated liquid line only being 17F above outdoor temp doesn't mean anything to you. Nor his SH being 7F too high. Both indicating the charge is probably low.
    True, if low airflow was the culprit SH would be low, not high. Are you using a chart to know what correct SH should be?

    I don't understand the how the SCT being 17 degrees higher that OAT indicates low charge. According to the chart for my system head pressure should only be 380 @ 100F OAT with 145 suction, he's go 400. Of course every system is different (this chart is specific to my system) and his may not even use a chart to charge. Is my system designed to run unusually low head pressures?
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  13. #13
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    Delta T chart

    The 31F superheat is high according to the R22 chart I have, should be 24F like you stated. (Chart says 22F but R410 may be different, close enough). According to the chart the 65 degree register temp is actually low, indicating poor airflow. The OP could be low on airflow and charge?

    Hope the charts are helpful to the OP on diagnosing his system.
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