New AC, finished build out, humid inside!

Old 09-28-13, 07:39 PM
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New AC, finished build out, humid inside!

My system is:


It cools pretty well, but the humidity in the 1300 square foot area it services is 60% at times. My dowstairs system keeps the house at 45-50% max. Any ideas? It was at 55% the other night at 78%, so I ran the thermostat and room down to 70 degrees and I managed to squeek out about 52% humidity. Its NOTICEABLY sticky in there when you walk in from the rest of the house. Is there something that needs to be done with the AC?
Old 09-29-13, 04:58 AM
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One thing you need to be aware of is that the term RELATIVE humidity is just that.
The % will change dramatically with the temperature you are taking the reading at, so as you lower the temperature in the space the RH % will rise as the temperature drops.

What you need to do is set the controls and leave the system for a reasonable length of time to stabilize...........24 - 36 hours would be the bare minimum!

As far as there being a problem with the system, if the unit has been properly installed and set up, looking at the run time would tell you a lot.
Might be over-sized if everything else is in order.
Old 09-29-13, 09:52 PM
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Call the installer back - the blower speed may be set too high. (too much capacity or excessive air leakage can cause the same issue)

Do you have the model number of the air handler or furnace?

Are there any bathrooms in the area that the system serves? Do you run exhaust fans when showering/cooking?

Is the area an addition? Keep in mind that it takes a while for building materials to dry out.
Old 09-30-13, 07:16 AM
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Im going to let it be for a week or two. This area is not an addition. Its basically 1200-1300 square feet of a second story that was never 'finished'. So, its basically been attic space and exposed to temps and humidity that an attic would be. There was some new material for framing, but not much. Just a few walls. perhaps everything does need to dry out. Ill keep an eye on it, its got a warranty of 2 years so its easy to have it tweaked.

In each register there is a piece of flat metal bent at an angle. It is riveted in place. It looks like some sort of damper, but it is not adjustable...its fixed. Does anyone have any clue what it is for or what it does?

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