New AC unit & evap coil, not cooling..
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  1. #1

    New AC unit & evap coil, not cooling..

    I have a rental house, it's a singlewide and it has a two ton unit. I replaced the condenser unit about a year ago with a Goodman R22 unit. It would never cool, the company came out, checked it, etc, but I could never get more than an 11 degree temperature drop. I finally contacted another company who said it was probably the mismatched coil, so they installed a new Goodman evaporator coil. We kept the original furnace and the new coil just sits on top of it in a closet area. Anyway, the new coil was installed and now I'm only getting 7-8 degree temperature drops. I don't get it... At first the company said it was a wrong piston size, so they replaced that and it's the exact same issue. I asked what the pressures on the unit were and if I remember correctly, it was around 78 psi and 190 psi and the temp inside was in the low to mid 80's and about the same outside...

    The tenants are not happy, and two companies now can't figure this out. I've researched a little and tried changing the fan speeds on the furnace and still have no changes..

    Any help would be greatly appreciated.. Please!!

  2. #2
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,410
    Can't diagnose from here, but sounds like a sizing problem with new system. Get the original installers back out and let them find the problem. You've had this problem since install about a year ago? What's the outside AC model and indoor A coil model??

  3. #3
    Quote Originally Posted by wahoo View Post
    Can't diagnose from here, but sounds like a sizing problem with new system. Get the original installers back out and let them find the problem. You've had this problem since install about a year ago? What's the outside AC model and indoor A coil model??

    That's what I originally thought, but even if a system wasn't large enough for the house, would it not still put out a cold temperature even though it wouldn't cool the house? My thoughts are it should still make the 16-20 (or whatever it is) temperature drop that a normal operating system does.... Of course, I could be flawed in that thought but that's just my personal experience with my very limited service knowledge.. I work as an installer for about 2 years during college and spent a month in the service department before getting canned, so I didn't learn too much!

    I believe the AC is a gsc13024 and the coil is a capf1824.

    Thanks!

  4. #4
    Join Date
    Jul 2007
    Location
    Delaware
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    3,824
    Is that not a down-flow unit? (supply vents in the floor)
    Always here

  5. #5
    Yes it is

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,597
    Gas or oil furnace?

    Should have asked them what the superheat and subcool were.

    A 2 ton unit with 1200 CFM of air going through it won't have a 20 degree split.

    Are you sure the old unit was 2 tons?
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  7. #7
    Join Date
    Apr 2010
    Location
    NC Sandhills
    Posts
    382
    What is your general location and approx size/age of mobile home? They are notorious for high infiltration and little insulation especially in ducting, around here a 2 Ton AC will be fighting a uphill battle, unless it is a newer home or low sqft. Like beenthere said the furnaces will mostlikely be pushing to much cfm for a 2 ton coil. If the blower speed was reduced it would increase temp split in cooling but can cause your heat exchanger to overheat in heating unless the controls change speed based on heat or cool call, a on site Tech will be able to diagnose.

  8. #8
    The AOP forums/Ask Our Pro's forums, are restricted to only Pro members that have been vetted by the AOPC can post advise, questions or commentary in a thread created by someone else. You need to apply for your vetting/* if you wish to participate in threads in the AOP forums. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.
    Last edited by beenthere; 09-10-2012 at 11:22 PM. Reason: Non Pro * Member

  9. #9
    Join Date
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    rage-red, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, questions or commentary in other peoples threads. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

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  10. #10
    Join Date
    Jul 2008
    Location
    Rochester NY
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    4,695
    4 tons!

    Instead of attempting to cool the great outdoors, ever consider sealing the beer can duct work?

    I did that on a 1700 sf double wide (& sealed some very leaky window trim and plumbing penetrations), and they cool very effectively with 1.5 ton! At this latitude we get some hot, LONG days.

    They HEAT with 40,000 btu, not even 4 ton.

    Take a camera, take the registers up, take 2-3 pictures in each direction. When you look ate the pictures on your computer you'll be shocked by all the visible leaks. Fix them, return too if you have one, and I bet the problem is solved.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  11. #11
    Quote Originally Posted by beenthere View Post
    Gas or oil furnace?

    Should have asked them what the superheat and subcool were.

    A 2 ton unit with 1200 CFM of air going through it won't have a 20 degree split.

    Are you sure the old unit was 2 tons?

    It's an electric furnace... What do you mean exactly about the 1200 CFM? I'm not really sure how that works, are you saying if the furnace blower is too big that it rushes past the coil too fast to cool or?

    & yes, the old unit was two tons also.. Or possibly even 1.5

  12. #12
    Quote Originally Posted by tedkidd View Post
    4 tons!

    Instead of attempting to cool the great outdoors, ever consider sealing the beer can duct work?

    I did that on a 1700 sf double wide (& sealed some very leaky window trim and plumbing penetrations), and they cool very effectively with 1.5 ton! At this latitude we get some hot, LONG days.

    They HEAT with 40,000 btu, not even 4 ton.

    Take a camera, take the registers up, take 2-3 pictures in each direction. When you look ate the pictures on your computer you'll be shocked by all the visible leaks. Fix them, return too if you have one, and I bet the problem is solved.

    I'm not sure what you mean about the 4 tons.... But, I'm pretty sure it's sealed up, I've looked and as I'm sure you know, it's just the long box, only has one trunk under the house.. I know it's a bad design but I have checked for leaks before, and there is no return, just an open area at the closet.

    The only thing I don't understand is, is a unit is properly charged, regardless or how it's sized for the building its in, would it still not put out a proper temperature drop even if it's not big enough to properly cool, but shouldn't it still cool the air it does put out?

  13. #13
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,410
    I think most mobine home indoor blowers are sized for 3 to 4 tons of air flow. If you are actually blowing 1200 cfm thru a two ton coil you'll have a real poor temp drop thru coil. Slowing down the air flow will improve the size of temp. drop and improve de-humidification. With only 8 degree drop, you're not getting hardly any de-humidification of the air passing thru the coil. What is your subcool reading? I'll wager it's very high! In our area, we seldom see AC units smaller than 2 1/2 tons on M.Homes. Never seen a 2 ton AC in M.Home!

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