House humid after New coil


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Old 08-24-18, 02:17 AM
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House humid after New coil

We have been living in this house in TX for the last ten years and are the original owners. We have never had a humidity problem in the house until the other day when we had a new coil and plenum installed. The air feels cold but different than before, almost heavy is what my son described it as. I felt sweaty last night and that never happens. We have to keep turning it colder just to make it bearable. I've had the hvac guy out once to close a few dampers to get better air flow to some rooms but that doesn't help the humid feeling we are having. He also checked to make sure everything was sealed properly. I have a hygrometer snd it says around 52% in the bedroom. I know that doesnt sound very high but i cant explain the humid feeling. I'm not sure what is was before the coil/plenum change because it was never an issue. Please help this is driving me crazy thanks
 
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Old 08-24-18, 07:32 AM
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AC systems have no humidity control other than lowering temp.

If the temp is the same with the pre and post equipment then the relative humidity would be the same.
 
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Old 08-24-18, 10:46 AM
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Was the same size coil used as before?

A bigger coil may run warmer on a given capacity and remove less humidity.

If your existing unit is a 10 seer, a new coil rated for the same tonnage will be physically larger.

When the plenum was replaced, did they seal it properly to the duct and air handler or furnace? Supply Air leakage into unconditioned space can drive more moisture into the house by putting it into negative pressure.

Improper refrigerant charge - too much or too little can affect dehumidification.

When a unit is overcharged, the coil pressure is higher which correlates with a higher temperature.

When a unit is undercharged, there isn't enough refrigerant entering the coil and the end of each circuit is too warm, so it doesn't dehumidify properly.

Too high of a fan speed can also reduce dehumidification, but if they replaced the coil/plenum and left the speed alone, this shouldn't be an issue.

AC systems have no humidity control other than lowering temp.

If the temp is the same with the pre and post equipment then the relative humidity would be the same.
Actually they remove humidity by condensing moisture on the coil, which is colder than the temp the air is cooled down to.

An improperly set up a/c can cool without doing much dehumidifying. To dehumidify properly, the temp of the coil coil fins must be well below the indoor air dewpoint.
 
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Old 08-27-18, 06:55 AM
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I found an article that describes exactly what we are experiencing. A cold and clammy feeling. The article says the culprit is air leakage.

https://www.homecomfortexpertsinc.com/6428-2/
 
 

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