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Old 06-26-2012, 04:31 PM   #1
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AC blows warm air as outside temp rises


Wife and I had central air installed in our home just a couple years ago. Every summer when the temperature rises into the high 80's and above I notice that the AC runs all day and cannot meet demand, which is usually set to 74. The split between air out and in narrows as the outside temp rises into the high 80's. On the worst of days during heat waves (high 90's and high humidity) the inside temp reaches 81! Air out during this time is around 74....? We have insulated flexible duct running in the attic. Is it possible that the insulated duct isn't insulated enough?

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Old 06-26-2012, 04:39 PM   #2
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AC blows warm air as outside temp rises


Has it gotten that hot before and functioned normally? OR Is this the first time it's been this hot and it hasn't performed as you've expected?

IF it worked well prior to this year even in hot weather, it may be due to a refrigerant leak from the system, which can reduce the cooling capacity of the system. You'll need to call an HVAC company to service the unit if that's the case.

IF it's never gotten this hot and the system is struggling with the high temps then you may have some serious systemic problems like: an insufficiently sized air conditioner; a lack of proper returns or air supply. Neither of these are cheap and fast repairs. Either way, you'll probably need to have it looked at by a pro.

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Old 06-26-2012, 05:43 PM   #3
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AC blows warm air as outside temp rises


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Originally Posted by jaf4uall View Post
Wife and I had central air installed in our home just a couple years ago. Every summer when the temperature rises into the high 80's and above I notice that the AC runs all day and cannot meet demand, which is usually set to 74. The split between air out and in narrows as the outside temp rises into the high 80's. On the worst of days during heat waves (high 90's and high humidity) the inside temp reaches 81! Air out during this time is around 74....? We have insulated flexible duct running in the attic. Is it possible that the insulated duct isn't insulated enough?
It's possible, but it's not likely to be the sole cause of that degree of bad performance. The flex duct should be R6 or better and shiny on the outside (reflective barrier).

You need to stick a thermometer into the air flow on each side of the evaporator coil to get the true split. Then stick the thermometer up in the supply and return grilles. Then you can compare. Use a digital probe thermometer. For example, a Weber grill thermometer works fine. If you drill holes in your plenum to insert the thermometer, be sure not to drill through the coil or anything else! Note that the split measured in the house will tend to decrease with the lengths of the duct runs. If you have some short runs and long runs, it may help to balance the air flow if that hasn't already been done.

What's the air flow like? Does it decrease as the system fails to keep up? That could indicate the coil is freezing over, a sign of low charge.

You really need to get your installer out to get it working right, as it sounds like it never has. Then get a second opinion from a different company if necessary.
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Old 06-27-2012, 12:40 AM   #4
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AC blows warm air as outside temp rises


I'm guessing from the tone of the first post that it never worked right. Correct?
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