Results 1 to 9 of 9
  1. #1
    Join Date
    Jan 2005
    Posts
    152
    Just had an AmericanStandard installed today, 2.5 ton, vari-speed AH. I'm achieving my setpoint OK, but it seems that my old AC felt colder coming out of the supply.

    Question: As a rule of thumb, what's the normal temp drop that installers usually look for? I thought it was between 10 and 20 degrees. If I'm not obtaining the proper temp delta, I'm guessing it'd be a good idea to have the contractor back out to check the charge? Also: I noticed that he didn't consult the super-cooling chart in the setup instructions, and use the 10degree supercooling number written on the condenser.

    If you charge until the guages 'look right', you might not charge it properly, correct?

  2. #2
    Join Date
    Jul 2006
    Location
    Southern CT
    Posts
    552
    You are worrying about nothing. You said that you are achieving setpoint, that would indicate that the system is working ok. Give it time...discharge air temp is not the only factor if a system is correct. Example: measure your supply air temp with clean filter, then block off 3/4 of the filter with cardboard. I'll bet your supply temp drops, but the system wouldn't work correctly like that. Relax, and enjoy the new system ;-)

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,420
    American-Standard gives a head & suction pressure to look for under indoor & outdoor conditions and the coil you have installed.

    What's the humidity? Did they set the blower speed for 400 CFM per ton?

    It would be nice to see 20 drop over the coil (don't read at grilles) but with high humidity, much less than that could be right.

  4. #4
    Join Date
    Jul 2004
    Location
    Winston-Salem,Nc
    Posts
    350
    is the outdoor unit single or multistage?

  5. #5
    Join Date
    Jan 2005
    Posts
    152
    Outdoor unit is a 13SEER single-stage. It did take a while before all the humidity was removed in the house - the old unit was dead and the house was 83 when the AC was turned on, and who knows how high the humidity was...

    However: the house has been 77 degrees all nite, and I just turned it on; been running for 20 mins, and the air coming from the supplies still doesn't seem as cold as other A/C's I'd felt.

    Question: With the temp about ~2-3 degrees away from setpoint, and the humidity in-line with what's expected with the A/C running, is a 20degree split still a good rule of thumb?

  6. #6
    Join Date
    Jul 2006
    Posts
    1,091
    Old to new unit is not a good comparisum, like pysch said airflow makes a difference. I'm sure your old coil was not spotless. And remember... everything in your home was 83 when the unit was turn on (thermal storage). Youre not just cooling your air (removing heat), but your books, your couch, your... every soild/liquid matter.

  7. #7
    Join Date
    Jan 2005
    Posts
    152
    I started another post, related to the fact that it seems that the air from my supply gets colder, as the OD temp goes up. The temp is 93 now, and the air seems colder now, than it did when it was 75 last nite.

    As OD temp goes up, the refer pressure raises a bit - if this is the case, and I'm getting colder as the refer pressure goes up, does that mean my pressure is too low, as the system was charged when installed yesterday?

  8. #8
    Join Date
    Jan 2005
    Posts
    152
    This morning, I measured the temp delta. Air entering was 76, and the air emerging from the first floor outlet closest to the AH was 61. The unit had been running for 45 mins with the compressor on.

    Is a temp drop of 15 degrees sufficient? OD temp at the time was ~85.

    I checked the dip switches, and the unit is set for 400 cfm. It has settings for low/high 350/450 respectively. Comfort-R is enabled.

  9. #9
    Join Date
    Sep 2002
    Location
    I don't know
    Posts
    2,897
    It's perfectly normal if the system is removing a lot of humidity. It takes at least a couple of days to dry out a house.

    15 is not too bad regardless; you need to check the outlet temp right at the air handler for an accurate reading. It's probably working fine; don't worry about it.

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