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  1. #1
    Join Date
    Jul 2008
    Posts
    5

    Carrier furnace with new A/c and low airflow

    Hi, I just had A/C installed to my home which is 2 years old. My furnace is a Carrier 58STX90-16 which had great air flow on heat mode throughout my house. I had a local contractor install a Ducane system with a matched 4 ton coil in the attic. He had to move the ducting distribution box to make room for the coil. Since then my air flow has been dismal. I contacted the installer with my problem and he was of little help. I went ahead and contacted another local contractor who came out and said that the unit was 1lb low on freon and he fixed a condensation leak in the attic. He also didn't have an answer to why the low air flow. Now today I've been testing the a/c to see if it could keep my house at 75 degrees. Right now it's 86 outside and the a/c is running constantly and it's 77 inside my home. I checked the small copper line going to the condensor because i was told it should be warm and it's not. Please help with some guidance if you could I'm getting tired of throwing money at this unit with no support from these contractors...

    Thank You...

    Mike

  2. #2
    Join Date
    Jul 2008
    Posts
    33
    It sounds like the installing contractor needs to address and fix the problem. Have them do a static pressure test, and check airflow compared to size of unit. A reputable contractor will fix the problem.

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,090
    Well. You may have gone with the wrong bid.
    Not to bust on Ducane. But many times its used by lower priced contractors that don't test systems to see if the existing duct work can handle the coils restriction.

    Good chance, that as you expect, teh install is not corect.

    Can you post pics of teh A/C coil box, and how teh ducts are attached to it.

    From your description, we can't tell anything.
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    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Jul 2008
    Posts
    5
    Thanks for the replies. The original contractor is giving me the run around and as you suspect my budget is tight and I went with the low bid but now my budget is out the window. I'll get some pics posted...

  5. #5
    Join Date
    Jul 2008
    Posts
    20

    here i am

    whats ur temperature difference between supply and return duct

  6. #6
    Join Date
    Jul 2008
    Posts
    5

  7. #7
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Is that a flexible dryer vent on the flue line? Not sure if that's code, but I'd want rigid material to carry those harmful flue gases. If you can get close enough to the distribution box, do you feel any major air loss?

  8. #8
    Join Date
    Jul 2008
    Posts
    5
    The flue is a flexible metal tubing of some sort, I would assume it's code the house was new construction as of 2 years ago but you never know. I checked all around the coil for any significant air loss and I don't feel any. Could it be possible that my blower just isn't strong enough for this coil even though it is supposedly matched or could there be an obstruction between the furnace and coil?

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,090
    That looks like a flexable B vent connector section. Its code approved. Atleast here it is.

    It looks like the coil is 3 or 4" narrower then the furnace, and if it is. That means it could be restricting the air flow.

    I have no idea why that drain pipe is going in to the supply plenum.
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  10. #10
    Join Date
    Apr 2008
    Location
    Alberta Canada
    Posts
    2,246

    You are pushing it

    That furnace is 1600 CFM Max The plenium Coil looks small better be at least 18" round supply duct or 14" x 20" rect duct coming off plenium. You can increase motor to 2000 CFMs if duct work is not problem
    Do it right the first time.

  11. #11
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,743
    that was a take the money and run job......


    since you will probably never see them again you might want to call another contractor to see if it can be straightend out.

  12. #12
    Join Date
    Jul 2008
    Posts
    5
    Yeah it definitely looks and feels like a take the money and run job. At this point I'm trying to locate a competent contractor in my area who can adequately fix my issue. Should I be requesting an increase in the CFM from my blower or is the coil the issue since it is smaller than the furnace? My hopes are that the next contractor will be able to diagnose and fix this properly.

    Thanks for the input!

  13. #13
    Join Date
    Feb 2008
    Location
    Dallas & Longview, TX
    Posts
    629
    Ouch!

    The next contractor should check the static before increasing CFM. It could be the coil or the plenum. Glad to see the plenum drain though!

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